Question: Atherosclerosis is due to

Atherosclerosis is a slowly progressive disease of large to medium-sized muscular aeries and large elastic aeries characterised by elevated focal intimal fibrofattyPlaques. Principal larger vessels affected are the abdominal aoa, descending thoracic aoa, internal carotid aeries and medium to smaller sized vessels affected are popliteal aeries, coronary aeries, and circle of Willis in brain. The atheroma may be preceded by fatty streaks that are intimal collection of lipid-laden macrophages and smooth muscle cells, occurring in persons as young as one year of age.The disease typically manifests in later life as the vessel lumen is compromised, predisposing to thrombosis and the underlying media is thinned, predisposing to aneurysm formation. It is the number one killer disease, 50 per cent of all deaths in the USA are attributed to atherosclerosis and half of theseare due to acute myocardial infarctions. The remainder include cerebrovascular accidents ("stroke"), aneurysm rupture, mesenteric occlusion and gangrene of theextremities. Etiological Factors Major risk factors in CHD have been discussed earlier. Risk of developing atherosclerosis increases with age, a positive family history, cigarette smoking, diabetes mellitus, hypeension, and hypercholesterolemia. The risk is correlated with elevated LDL and inversely related to the HDL level. Hereditary defects, e.g. familial hypercholesterolemia involving the LDL receptor or the LDL apoproteins cause elevated LDL, hypercholesterolemia andaccelerated atherosclerosis. Lesser influences on the risk of atherosclerosis include sedentary, or high-stress lifestyle, obesity and oral contraceptives.Ref: M.N. Chatterjee - Textbook of Biochemistry, 8th edition, page no: 454 - 456


Question: Water is a poor conductor of electricity because it is

Ans: a (Non ionised) Reg: Harper's 27th ed/p.5,6Pure water (de ionised water) is a poor conductor of electricity. The electrical conductance of water increases when there are impurities (salts), resulting in more number of ions for electrical conduction.A water molecule is an irregular, slightly skewed tetrahedron with oxygen at its center. It is a strong dipole, with high dielectric constant of 78.5 which enable water to dissolve large quantities of charged compounds such as salts.Water is an excellent nucleophile.


Question: The technique for accurate quantification of gene expression is

PCR Real-time PCR Traditional PCR For accurate quantification of the amount of initial DNA in the reaction Detects the DNA by electrophoresis at the end-point of the reaction


Question: The end product of one stage fermentation is

All other guides have given ethanol as the answer to this question. Which is incorrect.
One stage fermentation here means fermentation of pyruvate in one stage.
When pyruvate is formed, it can have several fates.
Under aerobic conditions, pyruvate enters the TCA cycle after conversion into acetyl CoA by PDH.
There are two fates for pyruvate under anaerobic metabolism:-


Question: The fluid mosaic model of membrane structure was proposed by


Question: Vitamin k epoxide cycle is seen in

Reference: Harpers illustrated biochemistry 30th edition


Question: In Hanup's disease, the following amino acids are excreted into the urine

Hanup disease reflects impaired intestinal and renal transpo of tryptophan and other neutral amino acids.The defect limits tryptophan availability for niacin biosynthesis and accounts for the pellagra-like signs and symptomsHarper 30th edition Pg: 308


Question: Keratosis is a feature of deficiency of


Question: The end product of cytosol fatty acid synthetase in humans is

ahnitic acid
In fatty acid synthesis
1.Primary substrate        →   Glucose
2. Immediate substrate   →   Acetyl-CoA
3. End product               →  Palmitate (Palmitic acid)


Question: GABA (Gamma amino butyric acid) is characteristic of

Functions of GABA:- One of the major inhibitory neurotransmitters in brain. Regulates the activity of neurons by discouraging the transmission signals It is believed that GABA opens chloride channels & (|||) the permeability of post-synaptic membranes. (|) GABA levels will cause excitation in brain leading to convulsions

Classification and metabolism of amino acids


Question: Supercoiled DNA is separated by relaxed DNA by

Gel electrophoresis is a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores.ELISA (enzyme-linked immunosorbent assay) is a plate-based assay technique designed for detecting and quantifying substances such as peptides, proteins, antibodies, and hormones.DNA fingerprinting is a test to identify and evaluate the genetic information--called DNA(deoxyribonucleic acid)--in a person&;s cells.DNA footprinting is a method of investigating the sequence specificity of DNA-binding proteins in vitro. This technique can be used to study protein-DNA interactions both outside and within cells.


Question: At the physiological pH the DNA molecules are

Ans. is 'b' i.e. Negatively charged DNA molecules are negatively charged, this is evident as it is stained by a cationic (positively charged) dye.Read the following lines for Ronald Hoffman Hematology:"Anionic cellular elements (nuclear DNA) reacts with cationic dye (Methylene blue)"


Question: Coris disease is due to defect in

It is type III glycogen storage disease. to deficiency of the debranching enzyme. Clinical features: highly branched dextrin accumulate, fasting hypoglycemia, hepatomegaly.Ref: DM Vasudevan, 7th edition, page no: 125


Question: Transaldolase is a

Transaldolase 1 is a key enzyme of the nonoxidative pentose phosphate pathway providing ribose-5-phosphate for nucleic acid synthesis and NADPH for lipid biosynthesis. This pathway can also maintain glutathione at a reduced state and thus protect sulfhydryl groups and cellular integrity from oxygen radicals. The residue of lysine-142 in the active site of transaldolase forms a Schiff base with the keto group in sedoheptulose-7-phosphate after deprotonation by another active site residue, glutamate-106. The reaction mechanism is similar to the reverse reaction catalyzed by aldolase: The bond joining carbons 3 and 4 is broken, leaving dihydroxyacetonejoined to the enzyme a Schiff base. This cleavage reaction generates the unusual aldose sugar erythrose-4-phosphate. Then transaldolase catalyzes the condensation of glyceraldehyde-3-phosphate with the Schiff base of dihydroxyacetone, yielding enzyme-bound fructose 6-phosphate. Hydrolysis of the Schiff base liberates free fructose 6-phosphate, one of the products of the pentose phosphate pathway.Ref: DM Vasudevan, Page no: 691


Question: Km is increased, but Vmax remains same. The enzyme inhibition is

Features of non-competitive inhibition

Inhibitor have no structural resemblance to substrate.
Mostly irreversible (Except a few reversible non-competitive inhibition).
Excess substrate do not abolish the inhibition.
Km remains the same.
Vmax decreases.

Features of competitive inhibition

Inhibitor will be structural analogue of substrate.
Reversible .
Excess substrate abolish the inhibition.
Km increases.
Vmax remains the same.


Question: Nucleoside is made up of

Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a 5-carbon sugar (either ribose or deoxyribose)


Question: Ketone bodies not utilised by

Paial oxidation of fatty acids in the liver leads to ketone body production. Ketone bodies are expoed to extrahepatic tissues, where they act as a fuel in prolonged fasting and starvation.


Question: Alpha helix of primary polypeptide structure is stabilized by

The alpha helix is the most common and stable conformation for a polypeptide chain.In proteins like hemogloin and myoglobin, the alpha helix is abundant. The alpha helix is aspiral structure .The polypeptide bonds form the bacbone and the side chains of aminoacids extend outward.The structure is stabilized by hydrogen bonds between NH and C=O groups of the main chain. REFERENCE :DM VASUDEVAN TEXTBOOK EIGHTH EDITION; Page no:39


Question: Uncontrolled phagocytosis of oxidized LDL paicles is a major stimulus for the development of foam cells and fatty streaks in the vascular subendothelium. This process may be inhibited by increased dietary intake of

Oxidation of lipid and protein poion of LDL is deleterious Oxidised LDL is taken up by scavenger receptors of the macrophages and leads to foam cell formation. This promotes atherosclerosis. Thus, it is impoant to prevent the oxidation of LDL. Vitamin E is the chain-breaking antioxidant that acts on the lipid phase of LDL and prevents lipid peroxidation. Other chain breaking antioxidants are Vit A, C; SOD; Uric acid Preventive antioxidants are glutathione peroxidase, catalase


Question: Alpha helix and Beta pleated sheet are examples of

Regions of ordered secondary structure arise when a series of aminoacyl residues adopt similar phi and psi angles. Extended segments of polypeptide (example, loops) can possess a variety of such angles. The angles that define the two most common types of secondary structure, the ` helix and the a sheet, fall within the lower and upper left-hand quadrants of a Ramachandran plot, respectively. Ref: Harper's Illustrated Biochemistry, 30E (2015) pg no 38.


Question: In porphyra cutanea tarda the type of porphyrin excreted in urine is

Porphyria cutanea tarda is also known as cutaneous hepatic porphyria. The paial deficiency of enzyme Uroporphyrinogen decarboxylase is responsible for the occurrence of porphyria cutanea tarda. Hence there is an increased excretion of uroporphyrins 1 and 3


Question: Xanthurenic acid is produced in

In the metabolism of Tryptophan, Kynurenin is an intermediate step. The accumulated Kynurenine is shunted to Xanthurenic acid. So, in pyridoxal deficiency, Xanthurenic acid is excreted in the urine.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 240


Question: AST/ALT > 2 is seen in deficiency of

The AST/ALT ratio is the ratio between the concentrations of the enzymes aspaate transaminase (AST) and alanine transaminase, aka alanine aminotransferase (ALT) in the blood of a human or animal. It is measured with a blood test and is sometimes useful in medical diagnosis to differentiate between causes of liver damage, or hepatotoxicity. the following are typical AST and ALT patterns relating to the "upper limit of normal" (ULN) Alcoholic fatty liver disease: AST > 8 times the ULN; ALT > 5 times the ULN Nonalcoholic fatty liver disease: AST and ALT > 4 times the ULN Acute viral hepatitis or toxin-related hepatitis with jaundice: AST and ALT > 25 times the ULN Ischemic hepatopathy (ischemic hepatitis, shock liver): AST and ALT > 50 times the ULN (in addition the lactate dehydrogenase is often markedly elevated) Chronic hepatitis C virus infection: Wide variability, typically normal to less than twice the ULN, rarely more than 10 times the ULN Chronic hepatitis B virus infection: Levels fluctuate; the AST and ALT may be normal, though most patients have mild to moderate elevations (approximately twice the ULN); with exacerbations, levels are more than 10 times the ULN Acid maltase deficiency (AMD) is an autosomal recessive disease characterized by an excessive accumulation of glycogen within lysosome-derived vacuoles in nearly all types of cells.


Question: Enzyme inhibited by insulin is

3. Hypoglycemic Effect of INSULINE - i. Insulin lowers the blood glucose level by promoting utilization and storage. ii. Gluconeogenesis is inhibited by insulin by repressing the key enzymes, pyruvate carboxylase (PC) phosphoenol pyruvate carboxykinase (PEPCK) and glucose-6- phosphatase. iii. Insulin inhibits glycogenolysis by oring the inactivation of glycogen phosphorylase and inhibiting glucose-6-phosphatase. The net effect of all these three mechanisms, blood glucose level is lowered. REF: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, EIGHTH EDITION,PG.NO.,167.


Question: Enzyme responsible for respiratory burst reaction


Question: Tryptophan is glucogenic & ketogenic by producing

The major metabolic fate of tryptophan is to be oxidized by tryptophan pyrrolase (tryptophan di-oxygenase) (Step 1, Fig. 17.8). It is a hemoprotein. The enzyme is inducible by coicosteroids.iii. In this major pathway, the total 11 carbon atoms of tryptophan are catabolized as formyl group (1C which enters the one-carbon pool), alanine (3C, entering the glucose pathway) and acetoacetate (4C, going to ketogenic pathway). So, tryptophan is both glucogenic and ketogenic. The remaining 3 carbons are removed as 3 CO2 molecules.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 211


Question: Statin action on HMG CoA reductase is

Inhibition result in decrease LDL receptors on hepatocytes


Question: Rate Limiting enzyme for Cholesterol synthesis is

(C) HMG Co-A reductase# 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase is the rate-controlling enzyme of the mevalonate pathway, the metabolic pathway that produces cholesterol and ther isoprenoids.Bio synthesis of Lipids - Multiple Steps IMPRTANT RATE-LIMITING ENZYME REACTIONSUrea cycleCarbamoyl phosphate synthetase IGlycolysisPFK-1GluconeogenesisFructose-1,6-bisphosphatase (reverses PFK-1 step)TCA cycleIsocitrate DHGlycogen synthesisGlycogen synthaseGlycogenolysisGlycogen phosphorylase (requires pryridoxal phosphate, the active form of B6)HMP shuntG6PD (deficient in "hemolysis IS PAIN" - INH, sulfonamides, primaquine, aspirin, ibuprofen, nitrofurantoin)De novo pyrimidine synthesisCarbamoyl phosphate synthetase li (combined orotic acid phosphoribosyltransferase/ orotidine-5-phosphate decarboxylase)De novo purine synthesisGlutamine-PRPP amidotransferase.Fatty acid synthesisFatty acid oxidationAcetyl-CoA carboxylase (ACC)Carnitine acyltransferase IKetogenesisHMG-CoA synthaseCatecholamine synthesisTyrosine hydroxylaseCholesterol synthesisHMG-CoA reductase (blocked by statins)


Question: Copper is a constituent of the enzyme

Role in Enzyme Action: Cu forms integral pa of ceain enzymes, e.g. some of cytochromes, cytochrome oxidase, tyrosinase, Monoamine oxidase (MAO), Lysyl oxidase, Catalase, Ascorbic acid oxidase, uricase and superoxide dismutase. These enzymes contain about 550 mg of Cu per gram of enzyme proteinRef: MN Chatterjea Textbook of Medical Biochemistry, 6th edition, page no: 622


Question: Essential pentosuria is due to defect in

It is an inborn error of metabolism.In the pathway, L-xylulose is conveed to D-xylulose by two enzymes, xylitol dehydrogenase, and xylulose reductase.Absence of any of these enzymes leads to pentosuria.Ref: DM Vasudevan, 7th edition, page no: 135


Question: The daily requirement of protein for the adults is


Question: Stop codon

They do not code for any amino acid Mark the end of protein synthesisOther stop codons are UAA UGARef: DM Vasudevan, 7th edition, page no: 599


Question: During the formation of hydroxyproline and hydroxylysine, the essential factors required is/are

In Collagen Synthesis: Vitamin C is required for the post-translational modification, Hydroxylation of lysine and Proline Vitamin C plays the role of a coenzyme The hydroxylation reaction is catalysed by lysyl hydroxylase (for lysine) and prolyl hydroxylase (for proline) this reaction is dependent on vitamin C(ascorbic acid), molecular oxygen and alpha-ketoglutarate Hydroxyproline and hydroxylysine are essential for the collagen cross-linking and the strength of the fibre Ref: Satyanarayana 4th ed page 132


Question: Vitamin B12 deficiency leads to accumulation of

(D) Methylmalonyl-CoA # Vit B12 deficiency leads to megaloblastic anemia.> B12 (cobalamin) is involved in the isomerization of methylmalonyl coenzyme Ato succinyl coenzyme A, requiring adenosylcobalamin as a prosthetic group on the enzyme methylmalonyl- coenzyme A mutase.> A deficiency of vitamin B12 thus leads to increased levels of methylmalonate, excreted in the urine as methylmalonic acid. Interruption of the succinyl pathway with the build-up of increased levels of methylmalonate and propionate (a precursor) could lead to the formation of abnormal fatty acids that may be incorporated into neuronal lipids.> Beta oxidation of saturated fatty acids with odd number of carbon atoms proceeds as follows: Propionyl CoA with biotin (Propionyl CoA carboxylase) forms methylmalonyl CoA which is converted to succinyl CoA due to methylmalonyl CoA mutase (vitamin B12 as coenzyme) Deficiency of vitamin B12 leads to methylmalonyl aciduria.


Question: In Gaucher&;s diseases, there is deficiency of

Enzyme defect Gaucher&;s disease. Beta glucosidase is deficient Salient features: -Glucocerebroside accumulate. adult, infantile, juvenile. Hepatosplenomegaly, erosion of bone, moderate anemia.Ref: DM Vasudevan, 7th edition, page no: 184


Question: Southern blot is used for

SOUTHERN BLOT : It is based on the specific base pairing propeies of complementary nucleic acid strands ,this technique is based on DNA hybridization. DNA is isolated from the tissue.It is then fragmented by restiction endonucleases.The cut pieces are electrophoresed on agarose gel. Treatment with NaOH denatures the DNA, so that the pieces become single stranded. This is then blotted over to a nitrocellulose membrane .The ssDNA is adsorbed on the nitrocellulose membrane. An exact replica of the pattern in the gel is reproduced on the membrane. REF :DM VASUDEVAN TEXTBOOK; 8th edition;Page no :609


Question: Vitamin also acting as hormonea) Vitamin Db) Vitamin Ac) Vitamin B1d) Vitamin C

Vitamin A and vitamin D are actually hormones which act on intracellular receptors (steroid receptor family).


Question: An essential amino acid in man is

Isoleucine, Leucine, Threonine, Lysine, Methionine, Phenylalanine, Tryptophan, and Valine are essential amino acids.
Reference: Vasudevan 7th  ed, pg 27


Question: Unsaturated fatty acids are synthesized in the

Most of the activity of these enzymes in the biosynthesis of triacylglycerols resides in the endoplasmic reticulum, but some are found in mitochondria.Ref: Harper&;s Biochemistry; 30th edition; Chapter 24; Metabolism of Acylglycerols & Sphingolipids


Question: Fatty acid sythase complex does not include

Fatty acid synthase complex is a multienzyme complex The complex is a dimer of two identical polypeptide monomers arranged in an X-shape in which six enzymes and acyl carrier protein are linked in primary structure. Reference: Harpers illustrated biochemistry 30 th edition


Question: Pentose pathway produces

The major purpose of the pentose phosphate pathway is generation of reduced NADPH and pentose phosphates for nucleotide synthesis.Ref: DM Vasudevan, 7th edition, page no: 130


Question: Vitamin required for post translational modification of coagulants is


Question: A different sequence of amino acids having a similar structure of proteins is an example of

Divergence and convergence are two evolutionary processes by which organisms become adapted to their environments.
Convergence has been defined as the acquisition of morphologically similar traits between distinctly unrelated
organisms.
Convergence occurs at every level of biological organization.

Functional Convergence

This refers to molecules that serve the same function but have no sequence or structural similarity and carry out their function by entirely different mechanisms.

Mechanistic convergence

Mechanistic convergence occurs when the sequence and structure of molecules are very different but the mechanisms by which they act are similar.

Structural Convergence

This refers to molecules with very different amino acid sequences that can assume similar structural motifs, which may carry out similar functions.

Sequence Convergence

In sequence convergence, one or more critical amino acids or an amino acid sequence of two proteins come to resemble each other due to natural selection. (In protein evolution, sequence divergence, rather than sequence convergence is the rule.)


Question: Uric acid is formed by

Uric acid the end product of purine catabolismis a strong reducing agent. Its role as an antioxidant is paicularly significant in the upper respiratory tract REF : DM VASUDEVAN TEXTBOOK ;8th EDITION ;Page no:547 and 548


Question: In chronic diabetics the value of TG and VLDL are more because

Insulin Activates Lipoprotein lipase Inhibits Hormone sensitive lipase (HSL) In diabetic condition opposite will occur, i.e. Increased activity of hormone sensitive lipase and decreased lipoprotein lipase activity. Increased activity of hormone sensitive lipase Catabolic activity of Fatty acid in Blood

Increase in peripheral function of LDL receptors

Increased activity of lipoprotein lipase and decreased activity of hormone sensitive lipase


Question: Active sites of serine protease contain

Serine proteases name stems from the nucleophilic Ser (serine) in the enzyme active site Nucleophilicity of the catalytic Ser is typically dependent on a catalytic triad of Asp, His, and Ser residues, commonly referred to as the charge relay system Ref: biochemistry by U. Satyanarayana 3rd edition Pgno : 171


Question: "Indican" is a metabolite of

Indian is a major excretory product in the metabolism of tryptophanRef: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 242, fig 18.11


Question: Enzyme deficient in alkaptonuria is

Ans. a (Homogentisic acid oxidase). (Ref. Harper, Biochemistry, 25th ed., 332)Disorders of amino acid and urea cycle metabolismAmino acid metabolism NameEnzyme deficiencyMetabolism affected1AlbinismTyrosinaseTyrosine2AlkaptonuriaHomogentisate oxidasePhenylalanine, tyrosine3CystathioninuriaCystathionine lyaseCysteine, methionine, serine4HistidinemiaHistidine ammonia lyaseHistidine5HomocystinuriaCysthionine sythaseCysteine, methionine, serine6Maple syrup urine diseaseBranched-chain keto acid dehydrogenaseValine, isoleucine, leucine7Phenylketonuria(PKU)Phenylanine hydroxylasePhenylalanine8TyrosinosisHydroxyphenylpyruvate hydroxylaseTyrosine transaminase Urea cycle1ArgininemiaArginase2ArgininosuccinaturiaArgininosuccinate lyase3CitrullinemiaArgininosuccinate synthetase4Hyperammonemia-IOrnithine transcarbamoylase5Hyperammonemia-llCarbamoyl-phosphate synthetase-l


Question: Digestive enzymes are

Hydrolases are any class of enzymes which catalyze the hydrolysis of proteins, nucleic acids, starch, fats, phosphate esters, and other macromolecular substances. The hydrolysis is carried out through the addition of water. Digestive enzymes carry out their function in this way, hence they are called hydrolase Enzymes are globular proteins that control biological reactions. Digestive enzymes speed up the breakdown (hydrolysis) of food molecules into their 'building block' components. These reactions occur outside of the cells lining the gut.


Question: Folding of nascent polypeptide chains is the function of

In molecular biology, molecular chaperones are proteins that assist the covalent folding or unfolding and the assembly or disassembly of other macromolecular structures. Chaperones are present when the macromolecules perform their normal biological functions and have correctly completed the processes of folding and/or assembly. The chaperones are concerned primarily with protein folding.


Question: Net gain of ATP in glycolysis

During the anaerobic (oxygen deficient) condition, when one molecule of glucose is conveed into 2 molecules of lactate, there is a net yield of 2 molecules of ATP. 4 molecules of ATP are synthesized by the 2 substrate level phosphorylations (steps 6 and 9). But 2 molecules of ATP are used in the steps 1 and 3, hence the net yield is only 2 ATP (Table 9.4). The whole reaction is summarized as Glucose + 2 Pi + 2 ADP --> 2 Lactate + 2 ATP iv.But when oxygen is in plenty, the two NADH molecules, generated in the glyceraldehyde3-phosphate dehydrogenase reaction (step 5), can enter the mitochondrial electron transpo chain for complete oxidation. As each NADH provides 2.5 ATPs, this reaction generates 2.5 x 2 = 5 ATPs. Thus when oxygen is available, the net gain of energy from the glycolysis pathway is 7 ATPs (Table 9.5).Hence the ATP yield from glycolysis is different in anaerobic and aerobic conditions.Ref: DM Vasudevan, 7th edition, page no: 112


Question: Genetic material possessing the dual capacity to exist chromosomal and extrachromosomal entity

An episome is a poion of genetic material that can exist independent of the main body of genetic material (called the chromosome) at some times, while at other times is able to integrate into the chromosome. Examples of episomes include inseion sequences and transposons. Viruses are another example of an episome. Viruses that integrate their genetic material into the host chromosome enable the viral nucleic acid to be produced along with the host genetic material in a nondestructive manner. As an autonomous unit (i.e., existing outside of the chromosome) however, the viral episome destroys the host cell as it commandeers the host&;s replication apparatuses to make new copies of itself. Read more: Episomes - DNA, Chromosome, Genetic, and Host - JRank AiclesRef: <a href="


Question: Branched chain ketoacid decarboxylation is defective in

Maple syrup urine disease is due to deficiency of the enzyme branched chain α-keto dehydrogenase which catalyzes decarboxylation of branched - chain amino acid.


Question: Modified nucleotide is seen in

Transfer ribonucleic acid (tRNA) is a type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein. tRNAs function at specific sites in the ribosome during translation, which is a process that synthesizes a protein from a mRNA molecule. Proteins are built from smaller units called amino acids, which are specified by three-nucleotide mRNA sequences called codons. Each codon represents a paicular amino acid, and each codon is recognized by a specific tRNA. The tRNA molecule has a distinctive folded structure with three hairpin loops that form the shape of a three-leafed clover. One of these hairpin loops contains a sequence called the anticodon, which can recognize and decode a mRNA codon. Each tRNA has its corresponding amino acid attached to its end. When a tRNA recognizes and binds to its corresponding codon in the ribosome, the tRNA transfers the appropriate amino acid to the end of the growing amino acid chain. Then the tRNAs and ribosome continue to decode the mRNA molecule until the entire sequence is translated into a protein.Ref:<a href="


Question: If starvation exceeds 7 days, the major nutritional supply of the brain comes from


Question: Most common physiological form of DNA

DNA can exist in at least six forms, i.e. A, B, C, D, E and Z.The B-form of DNA is the most common form of DNA and is right-handed helix.It is the strandard DNA structure with 10 base pairs per turn.Watson and Crick model describes the B-form of DNA.Other forms of DNA are A-form (contains 11 base pairs per turn and is right handed helix) and Z-form (contains 12 base pairs per turn and is left handed helix).Z-form is ored by alternating G-C sequences in alcohol and high salt solution; and is inhibited by alternating A-T sequnces (Note-B form has minimum base pairs per turn, i.e. 10).


Question: Deamination of the following amino acid occurs in liver

Deamination of glutamine occurs in liver and ammonia is released, which is converted to urea.


Question: Ketone body formation without glycosuria seen in


Question: Stop codons are

Terminator Codons : There are three codons which do not code for any paicular aminoacid.They ae "nonsense codons".more correctly termed as PUNCTUATOR OR TERMINATOR CODONS. They mark end of protein synthesis.These three codons are UAA,UAG,and UGA. UGA is a stop codon ,but in special circumstances,it stands for seleno-cysteine. REF :DM VASUDEVAN TEXTBOOK:7th EDITION ;Page no ;599.


Question: Rothera's test for detection of

Ketones

Rothera's nitroprusside - pink/purple permanganate ring test and Gerhard's - ferric chloride - red wine color tests are used for detection of ketone bodies in urine.


Question: Maximum energy is liberated by the hydrolysis of

Step 8 of Glycolysis - i. 2-phosphoglycerate is conveed to phosphoenol pyruvate by the enzyme enolase. One water molecule is removed. ii. A high energy phosphate bond is produced,so when it is hydrolysed max.energy is liberated. The reaction is reversible. iii. Enolase requires Mg++, and by removing magnesium ions, fluoride will irreversibly inhibit this enzyme. Thus, fluoride will stop the whole glycolysis. So when taking blood for sugar estimation, fluoride is added to blood. If not, glucose is metabolized by the blood cells, so that lower blood glucose values are obtained. Ref:DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY,EIGHTH EDITION,PG.NO.,131.


Question: Rate limiting enzyme in catecholamine biosynthesis is

Tyrosine Hydroxylase Is Rate-Limiting for Catecholamine BiosynthesisRef: Harper&;s Biochemistry; 30th edition; Chapter 41; The Diversity of the Endocrine System


Question: Dinitrophenol causes

Mechanism of Action of DNP as uncoupler Dinitrophenol (DNP) a potent uncoupler is ampipathic and increase the permeability of the lipoid inner mitochondrial membrane to protons (H+), thus reducing the electrochemical potential and sho-circuiting the ATP synthase. In this way, oxidation can proceed without phosphorylation. Note: DNP was used for weight loss. But it was discontinued due to hypehermia and other side effects.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 146

Uncoupling of oxidation and phosphorylation


Question: Enzyme responsible for complete oxidation of glucose to CO2 to water is present in

Ans. is 'b' i.e. Mitochondria The fate of pyruvate formed at the end of glycolysis (glucose metabolism) is as follows :Under anaerobic conditions : Pyruvate is reduced by the NADH to lactate in the presence of Lactate dehydrogenaseUnder aerobic conditions : Pyruvate is taken up into mitochondria & is converted to Acetyl-CoA in the presence of pyruvate dehydrogenase complex. Now this Acetyl-CoA enters Krebs cycle.* Kreb's cycle is the final pathway where oxidative metabolism of carbohydrates, amino acids & fatty acids converge, their carbon skeleton being converted to CO2 and H20.


Question: FIGLU is a metabolite of

FIGLU is metabolite in the histidine metabolism. Histidine is first non-oxidatively deaminated by histidase to form urocanic acid (step1). It is then hydrated to imidazolinone propionic acid (step 2) and then hydrolyzed to formimino glutamic acid (FIGLU) (step 3). Histidine ---->FIGLU------->Formimino THF Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 297


Question: An example of lyases is


Question: In the body, metabolism of 10 gms. of protein would produce approximately

Calorific value of nutrientsNutrientEnergy yield kcal/gramEnergy yield kjoule/gramRQ Carbohydrates4161 Fat937.71 Protein4.217.81 Alcohol728.66 Ref: Textbook of biochemistry (DM Vasudevan ), 6th edition, page no. 432


Question: In sickle cell anemia, glutamic acid is replaced by


Question: Lack of Homogentisate oxidase enzyme causes

(B) Alkaptonuria # ALKAPTONURIA: The defective enzyme in alkaptonuria is homogentisate oxidase in tyrosine metabolism. Homogentisate accumulates in tissues & blood, gets oxidized to the corresponding quinones, which polymerize to give black or brown colour. For this reason, the urine of alkaptonuric patients resembles coke in colour.


Question: vitamin involved in 1 carbon metabolism

THFA is the carrier of One Carbon groups The folic acid is first reduced to 7,8-dihydrofolic acid and fuher reduced to 5,6,7,8-tetrahydrofolic acid (THFA) . Both reactions are catalyzed by NADPH dependent folate reductase. The THFA is the carrier of one-carbon groups. One carbon compound is an organic molecule that contains only a single carbon atom. The following groups are one carbon compounds: Formyl (-CHO) Formimino (-CH=NH) Methenyl (-CH=) Methylene (-CH2-) Hydroxymethyl (-CH2OH) Methyl (-CH3). One carbon groups bind to THF through N5 are Formyl, Formimino or methyl N10 are Formyl Both N5 and N10 are Methylene and Metheny Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 475


Question: Vitamin that acts like a hormone

(D) Vitamin D # Vitamin D is a fat-soluble vitamin that acts as a steroid hormone.> Several hormones, including adrenal and gonadal steroid hormones, thyroid hormones, retinoid hormones, and vitamin D, bind with protein receptors inside the cell rather than in the cell membrane. Because these hormones are lipid soluble, they readily cross the cell membrane and interact with receptors in the cytoplasm or nucleus.> The activated hormone-receptor complex then binds with a specific regulatory (promoter) sequence of the DNA called the hormone response element, and in this manner either activates or represses transcription of specific genes and formation of messenger RNA (mRNA)


Question: Source of energy in kerb cycle is

ATP Generating Steps in TCA Cycle - There are 3 NADH molecules generated during one cycle, each of them will give rise to 2 1/2 ATPs on oxidation by electron transpo chain (ETC); so altogether they will give 3 x 2 1/2 = 7 1/2 (7.5) high energy phosphates. The FADH2 will generate 1 1/2 molecules of ATP. In addition, one molecule of GTP (equivalent to one molecule of ATP) is formed by substrate level phosphorylation. Hence, per turn of the cycle, 10 high energy phosphates are produced. STEP NO. REACTIONS COENZYMES ATPs 3 Isocitrate - alpha ketoglutarate NADH 2.5 4 Alpha ketoglutarate - succinyl CoA NADH 2.5 5 Succinyl CoA - Succinate GTP GTP 1 6 Succinate - Fumarate FADH2 1.5 8 Malate - Oxaloacetate NADH 2.5 TOTAL = 10 REF :DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, EIGHTHEDITION,PG.NO.,305,307.


Question: Enzymes increase reaction rates by

MECHANISM OF ENZYME ACTION
Explained by different theories:

Lowering of activation energy
Michaelis-Menten theory
Fischer’s Template theory
Koshland’s Induced Fit theory.

Lowering of Activation Energy
Enzymes lower the activation energy. Activation energy is defined as the energy required to convert all molecules of a reacting substance from ground state to transition state.


Question: Structure of antibodies is composed of

It is made up of 2 heavy (H) chains and 2 light (L) chains, combined through disulfide bridges. In the case of lgG, H chains are composed of 440 amino acids and L chains made up of 214 amino acids. Depending on the heavy chain makeup, the immunoglobulins are differentiated into 5 major classes.Immunoglobulin-G (lgG) is made up of heavy chain g (gamma)lgM has u (mu) heavy chainlgA has a (alpha) heavy chainlgD contains d (delta) lgE heavy chain is called e (epsilon).Ref: D M Vasudevan 7th edition Page no: 687


Question: Ketone bodies are synthesized

Ketogenesis Acetoacetate is the primary ketone body while beta-hydroxybutyrate and acetone are secondary ketone bodies. They are synthesized exclusively by the liver mitochondriaRef: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 143


Question: Splicing activity is a function of

A small nuclear RNA (snRNA) is one of many small RNA species confined to the nucleus; several of the snRNAs are involved in splicing or other RNA processing reactions.Small cytoplasmic RNAs (scRNA) are present in the cytoplasm and (sometimes are also found in the nucleus).snRNPs (snurp) are small nuclear ribonucleoproteins (snRNAs associated with proteins).scRNPs (scyrp) are small cytoplasmic ribonucleoproteins (scRNAs associated with proteins).The spliceosome is a complex formed by the snRNPs that are required for splicing together with additional protein factors.Anti-Sm is an autoimmune antiserum that defines the Sm epitope that is common to a group of proteins found in snRNPs that are involved in RNA splicing. The five snRNPs involved in splicing are U1, U2, U5, U4, and U6.Together with some additional proteins, the snRNPs from the spliceosome.All the snRNPs except U6 contain a conserved sequence that binds the Sm proteins that are recognized by antibodies generated in autoimmune disease.


Question: Fumarase is a

Class I Fumarase enzyme, EC 4.2.1.2 (fumarate hydratase), which catalyzes the reversible hydration of fumarate to L-malate. ... Aspaate ammonia-lyase, EC 4.3.1.1 (aspaase), which catalyzes the reversible conversion of aspaate to fumarate and ammonia. Fumarase (or fumarate hydratase) is an enzyme that catalyzes the reversible hydration/dehydration of fumarate to malate. Fumarase comes in two forms: mitochondrial and cytosolic. The mitochondrial isoenzyme is involved in the Krebs Cycle (also known as the Tricarboxylic Acid Cycle or the Citric Acid Cycle), and the cytosolic isoenzyme is involved in the metabolism of amino acids and fumarate. Subcellular localization is established by the presence of a signal sequence on the amino terminus in the mitochondrial form, while subcellular localization in the cytosolic form is established by the absence of the signal sequence found in the mitochondrial variety


Question: UV light causes mutation in cells by


Question: Enzyme used for cDNA synthesis is

Complementary DNA (cDNA) DNA that is complementary to RNA Reverse transcriptase (RNA dependent DNA polymerase) is used for the synthesis


Question: Trypsin cleavesa) Arginineb) Glutamatec) Lysined) Proline

Trypsin hydrolyses peptide bonds fornied by carboxy terminal of lysine and arginine


Question: Best marker of dyslipidemia


Question: At physiological pH, carboxy terminal of peptide is

In ion-exchange chromatography, proteins interact with the stationary phase by charge-charge interactions. Proteins with a net positive charge at a given pH will tightly adhere to beads with negatively charged functional groups such as carboxylates or sulfates (cation exchangers).

Harper, Ed 30, Pg 27


Question: Coenzyme required for tissue respiration is

Coenzyme Q (CoQ) is a quinone derivative with a long, hydrophobic isoprenoid tail. It is also called ubiquinone because it is ubiquitous in biologic systems. CoQ is a mobile carrier and can accept hydrogen atoms both from FMNH2, produced on NADH dehydrogenase (Complex I) and from FADH2, produced on succinate dehydrogenase (Complex II).Ref: Harpers Biochemistry; 30th edition


Question: Polymer of fructose

Ans. c (Inulin) (Ref. Ganong.-23rd/Ch. 38. 26th/pg. 105).Substances Used to Measure GFRIn addition to the requirement that it be freely filtered and neither reabsorbed nor secreted in the tubules, a substance suitable for measuring the GFR should be nontoxic and not metabolized by the body. Inulin, a polymer of fructose with a molecular weight of 5200 that is found in dahlia tubers, meets these criteria in humans and most animals and is extensively used to measure GFR. Radioisotopes such as 51Cr-EDTA are also used, but inulin remains the standard substance. In practice, a loading dose of inulin is administered intravenously, followed by a sustaining infusion to keep the arterial plasma level constant. After the inulin has equilibrated with body fluids, an accurately timed urine specimen is collected and a plasma sample obtained halfway through the collection. Plasma and urinary inulin concentrations are determined and the clearance calculated. The GFR in a healthy person of average size is approximately 125 mL/min.CLASSIFICATION OF IMPORTANT SUGARS AldosesKetosesTrioses (C3H6O3)GlyceroseDihydroxyacetoneTetroses (C4H8O4)ErythroseErythrulosePentoses (C5Hl0O5)RiboseRibuloseHexoses (C6H12O6)GlucoseFructoseHexoses of Physiologic ImportanceSugarSourceImportanceClinical significanceD-GlucoseFruit juices. Hydrolysis of starch, cane sugar, maltose and lactoseThe "sugar" of the body. The sugar carried by blood, and the principal one used by the tissuesPresent in the urine (glycosuria) in diabetes mellitus owing to raised blood glucose (hyperglycemia)D-fructoseFruit juices. Honey,Hydrolysis of cane sugar and of insulin (from the Jerusalem artichoke)Can be changed to glucose in the liver and so used in the bodyHereditary fructose intolerance leads to fructose accumulation and hypoglycemiaD-GalactoseHydrolysis of lactoseCan be changed to glucose in the liver and metabolized. Synthesized in the mammary gland to make the lactose of milk. A constituent of glycolipids and glycoproteinsFailure to metabolize leads to galactosemia and cataractD-Mann- OseHydrolysis of plant mannans and gumsA constituent of many glycoproteins Pentoses of Physiologic ImportanceSugarWhere foundBiochemical importance D-RiboseNucleic acidsStructural elements of nucleic acids and coenzymes, eg, ATP, NAD, NADP, flavoproteins. Ribose phosphates are intermediates in pentose phosphate pathway D-RibuloseFormed in metabolic processRibulose phosphate is an intermediate in pentose phosphate pathway D-ArabinoseGum arabic. Plum and cherry gumsConstituent of glycoproteins D-XyloseWood gums, proteoglycans, glycosaminoglycansConstituent of glycoproteins D-LyxoseHeart muscleA constituent of a lyxoflavin isolated from human heart muscle L-XyluloseIntermediate in uronic acid pathwayFound in urine in essential pentosuria DisaccharidesSugarSourceClinical significanceMaltoseDigestion by amylase or hydrolysis to starch.Germinating cereals and malt LactoseMilk, may occur in urine during pregnancy.In lactase deficiency, malabsorption leads to diarrhoea and flatulenceSucroseCane, and beet sugar. Sorghum.Pineapple carrot roots.In sucrase deficiency, malabsorption leads to diarrhoea and flatulenceTrehaloseFungi and yeasts.The major sugar of insect hemolymphGlucose Is one of the main hexoses absorbed from GIT, derived principally from dietary STARCH.


Question: Most non polar Amino Acid is

Non-polar amino acids are very much less polar than polar amino acids.
Among the given options, only leucine is non-polar.


Question: The most important source of reducing equivalents for fatty acid synthesis in the liver is

HMP pathway

The main source of NADPH for lipogenesis is the pentose phosphate pathway: PPP (also called the hexose monophosphate pathway: HMP).


Question: Increased level of lipoprotein(a) predisposes to

Atherosclerosis

Presence of lipoprotein (a) in blood in excessive amount increases the risk of coronary heart disease.
This could possibly be due to the structural resemblance of this apolipoprotein with plasminogen.
Because of close structural resemblance, LP(a) competes with plasminogen, thereby decreasing its conversion to plasmin.
Reduced plasmin activity results in decreased dissolution of clots. This, in turn, increases the susceptibility of an individual to atherosclerosis.


Question: Main source of energy derived from

Glycogen is the reserve carbohydrate in animals. It is stored in liver and muscles.The phosphorylated enzyme is less sensitive to allosteric inhibitors. Thus even if cellular ATP and glucose-6-phosphate are high, Phosphorylase will be active. The glucose-1-phosphate produced from glycogen in the liver may be conveed to free glucose for release to the blood.


Question: Cellular bearings of hereditary disease seen in

Hereditary information is preserved in DNA. Thus all genetic diseases are due to change in DNA.


Question: Rate limiting enzyme in glycolysis

Fructose-6-phosphate is fuher phosphorylated to fructose1,6 bisphosphate. The enzyme is phosphofructokinase. is the rate-limiting enzyme of glycolysis. It is an allosterically regulated enzyme catalyzes the second phosphorylation step of glycolysis using a second molecule of ATP is an impoant key enzyme of this pathwayRef: DM Vasudevan, 7th edition, page no: 109


Question: Krebs cycle and Urea cycle are linked at

Reference: Harpers illustrated biochemistry 30th edition


Question: The immediate precursor in the formation of acetoacetate from acetyl CoA in the liver is

HMG CoA

Acetoacetyl-CoA is the starting material for ketogenesis.

However, it is HMG-CoA from which acetoacetate arises.


Question: Sphingolipids are chiefly accumulated in

CNS

Sphingolipids are mainly found in cell membranes, particularly nerve cells and brain tissues.


Question: During prolonged starvation, the rate of gluconeogenesis depends on

Increased alanine levels in liver

In the fasting state, there is a considerable output of alanine from skeletal muscle, far in excess of its concentration in the muscle proteins that are being catabolized.
It is formed by transamination of pyruvate produced by glycolysis of muscle glycogen and is exported to the liver, where, after transamination back to pyruvate, it is a substrate for gluconeogenesis.
This is the glucose-alanine cycle. Which has two major functions:-

Transport of α -amino groups of amino acids (ammonium ion/ammonia) from muscle to liver
Transport of alanine as a substrate for gluconeogenesis

Decreased essential fatty acids in liver


Question: PCR requires

A primer is a sho strand of RNA or DNA (generally about 18-22 bases) that serves as a staing point for DNA synthesisPolymerase chain reaction uses DNA primers because they are more temperature stable. In experiments, it is often impoant to use a primer with a similar Tm to the template strand it will be hybridizing to.Ref: DM Vasudevan, 7th edition, page no: 638


Question: Serotonin is derived from

Serotonin is a metabolite of tryptophan Tryptophan ------------------->5hydroxy tryptophan ------------------>5hyroxy tryptamine (serotonin )Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 241


Question: Glucagon stimulates

Glucagon is a polypeptide hormone which is secreted by the A cells of the islets of Langerhans of pancreas. Glucagon is a group IIA hormone, i.e., acts by increasing cAMP. The actions of glucagon are somewhat opposite those of insulin.1) Glucagon stimulates glycogenolysis in the liver but not in muscle. Breakdown of glycogen yields glucose.2) Glucagon stimulates production of glucose from amino acids (gluconeogenesis). Both glycogenolysis and gluconeogenesis tend to raise plasma glucose level.3) Glucagon stimulates lipolysis. Breakdown of lipids yields free fatty acids, which may be oxidized completely to carbon dioxide, or incompletely to form ketone bodies


Question: McArdle’s disease is caused due to deficiency of


Question: The property of proteins to absorb ultraviolet rays of light is due to

Aromatic side chains (aromatic amino acids) are responsible for the UV light absorption of most proteins.


Question: Inhibition of glycogenolysis and gluconeogenesis is caused by

Insulin, a key inhibitor of hepatic glucose production, has effects on both glycogenolysis and gluconeogenesisRef: DM Vasudevan, 7th edition


Question: 25 hydroxylation of vitamin D occurs

Synthesis of 25-OH-D3 in Liver (Calcidiol)Vitamin D2 and/or D3 binds to specific D binding protein and is transpoed to liver.It undergoes hydroxylation at 25 position, by the enzyme 25-hydroxylase, in the endoplasmic reticulum of the mitochondria of liver cells.Coenzyme/cofactors required are: *Mg++NADPH, and *Molecular O2 A cytoplasmic factor is also required, the exact nature not known. Two enzymes, an NADPH-dependant cytochrome P450 reductase and a cytochrome P450 are involved also.25-OH-D3 (calcidiol) is the major storage form of vitamin D in liver and found in appreciable amount in circulation. The blood level of 25-OH-D3 exes feedback inhibition on the enzyme 25-hydroxylase. Reference: Chatterjea Textbook of Biochemistry pg no. 168


Question: Least post translational modification occurs in


Question: Mutarotation refers to change in

Mutarotation refers to the change in the specific optical rotation representing the interconversion of a- and b- anomers of D-glucose to an equilibrium. Ref: Biochemistry by U. Satyanarayana 3rd edition Pgno : 14


Question: Intermediate metabolite in TCA cycle are A/E

Pyruvic acid is a key substance in phase-II metabolism. 1. Principally it is formed from oxidation of glucose (glycolysis) by EM Pathway. Conversion of PA to OAA (by CO2-Fixation Reaction) Pyruvic acid can be conveed to oxaloacetate by the enzyme Pyruvate carboxylase. The enzyme requires: * 'Biotin' as a prosthetic group which brings CO2 * ATP and Mg++ * Requires 'acetyl-CoA' Acetyl-CoA does not enter into the reaction but may by combination with the enzyme maintains it in "active" conformation (+ve modifier). The generation of "acetyl-CoA" in metabolic reactions activates the enzyme and promote the formation of oxaloacetic acid (OAA) required for oxidation of acetyl-CoA in the TCA Cycle. Anaplerotic Reactions A sudden influx of Pyruvic acid (PA) or of "acetyl-CoA" to the TCA cycle might seriously deplete the supplies of OAA required for the citrate synthase reaction. Two reactions that are auxiliary to the TCA cycle operate to prevent this situation. These are known as anaplerotic (Filling up) reactions.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition, Page no: 334


Question: Vitamin required for collagen synthesis

The active form of vitamin C is ascorbic acid (Figure 28.8). The main function of ascorbate is as a reducing agent in several different reactions. Vitamin C has a well-documented role as a coenzyme in hydroxylation reactions, for example, hydroxylation of prolyl and lysyl residues of collagen (see p. 47). Vitamin C is, therefore, required for the maintenance of normal connective tissue, as well as for wound healing. Vitamin C also facilitates the absorption of dietary iron from the intestine.Deficiency of ascorbic acid A deficiency of ascorbic acid results in scurvy, a disease characterized by sore and spongy gums, loose teeth, fragile blood vessels, swollen joints, and anemia (Figure 28.9). Many of the deficiency symptoms can be explained by a deficiency in the hydroxylation of collagen, resulting in defective connective tissue.Ref: Lippincott, 5th edition, page no: 377


Question: A deficiency of substance B12 can result in an anemia. Choose the type of anemia that would occur if the substance were deficient.

Functions of vitamin B12 a. Vitamin B12 contains cobalt in a corrin ring that resembles a porphyrin.(1). Vitamin B12 is the cofactor for methylmalonyl-CoA mutase, which catalyzes the rearrangement of methylmalonyl-CoA to succinyl-CoA (see Fig below).(a). This reaction is involved in the production of succinyl-CoA from valine, isoleucine, threonine, methionine, and the propionyl-CoA formed by the oxidation of fatty acids with an odd number of carbons.(2). Vitamin B12 is involved in the transfer of methyl groups from FH4 to homocysteine to form methionine (see Figure below).A vitamin B12 deficiency results in a megaloblastic anemia plus demyelination of nerves, because of reduced levels of SAM in the nervous system. These cells are large because the vitamin deficiency interferes with DNA synthesis, and the cells double in size without being able to replicate their DNA. Once the anemia begins, the large blast cells are released by the marrow in an attempt to control the anemia. A hypochromic, microcytic anemia can result from the lack of iron, or lack of pyridoxal phosphate. Both conditions lead to a reduction in the synthesis of heme, so the red cells cannot carry as much oxygen (which gives them the pale color). The cells are small in order to maximize the concentration of hemoglobin present in the cells. Hemolytic anemia occurs when the red cell membrane fragments, which can occur with pyruvate kinase deficiencies or a lack of glucose-6-phosphate dehydrogenase activity (which results in reduced NADPH levels). Sickle cell anemia is caused by a point mutation in the b-globin gene, substituting a valine for a glutamic acid.The transfer of a 1-carbon unit from serine to deoxyuridine monophosphate (dUMP) to form deoxythymidine monophosphate (dTMP). FH4 is oxidized to FH2 in this reaction. FH2 is reduced to FH4 by dihydrofolate reductase. The rectangles indicate the steps at which the antimetabolites methotrexate and 5-fluorouracil act. FH2 , dihydrofolate; FH4 , tetrahydrofolate; NADP, nicotinamide adenine dinucleotide phosphate; NADPH, reduced NADP.


Question: Termination nucleotide sequence among following is


Question: Vit. B12 is absorbed in the

One molecule of IF can combine with 2 molecules of B12. This IF-B12 complex is attached with specific receptors on mucosal cells. The whole IF-B12 complex is internalized . It may be noted that B12 is absorbed from the ileum. Ref: DM Vasudevan, page no: 404


Question: The mineral having sparing action on vitamin E

The element selenium  is found in the enzyme glutathione  peroxidase  that  destroys  free radicals.  Thus, Se is also involved  in antioxidant functions like vitamin E, and both of them act synergistically.  To a certain extent, Se can spare the requirement  vitamin E, and vice versa.
Ref : Satyanarayana, 3rd ed, pg. 129


Question: The enzyme studied in Triphyenyl tetrazolium chloride test (TTC) to detect myocardial infarction is

Lactate dehydrodenase. TTC stain taken up depending on enzyme activity


Question: Glucose transporter in myocyte stimulated by insulin is

GLUT 4 is the transporter in muscle and adipose tissue that is stimulated by insulin.


Question: Total number of dehydrogenases in Krebs cycle

There are total 4 dehydrogenases present in kreb's cycle: 1. Isocitrate dehydrogenase 2. a- Ketoglutarate dehydrogenase complex 3. Succinate dehydrogenase 4. Malate dehydrogenase


Question: Albinism results from the deficiency of

Homogentisic acid oxidase: ALKAPTONURIA Phenylalanine hydroxylase: PHENYLKETONURIA Tyrosinase: ALBINISM Xanthine oxidase: URIC ACID SYNTHESIS ENZYME Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 353


Question: First substrate of Kreb’s cycle is

Pyruvate, the end product of aerobic glycolysis is transported into mitochondria by specific pyruvate transporter, where it is converted to acetyl CoA by pyruvate dehydrogenase (PDH) complex.


Question: The metabolite accumulating in Wolman&;s disease is

Wolman Disease and Cholesteryl Ester Storage Disease:These autosomal recessive disorders are caused by lack of lysosomal acid lipase. After LDL cholesterol is incorporated into the cell by endocytosis,it is delivered to lysosomes where it is hydrolyzed by lysosomal lipase. Failure of hydrolysis because of the complete absence of the enzyme causes accumulation of cholesteryl esters within the cells. Hepatosplenomegaly, steatorrhea, and failure to thrive occur during early infancy, leading to death at the age of 1 yr.In cholesterol ester storage disease, a less-severe form than Wolman disease, there is low but detectable acid lipase activity.Reference: Nelson Textbook of Paediatrics; 20th edition; Chapter 86; Defects in Metabolism of Lipids


Question: Cofactor for Glycogen phosphorylase in Glycogenolysis is

Glycogen phosphorylase removes glucose as glucose-6- phosphate from glycogen. It contains pyridoxal phosphate as prosthetic group.Ref: DM Vasudevan, 7th edition, page no: 124


Question: Positive nitrogen balance is seen in


Question: In a well fed state, acetyl CoA obtained from diet is least used in the synthesis of

Ketone bodies (acetoacetate) synthesis is decreased in fed state, so acetyl-CoA is not used for synthesis of ketone bodies in fed state.

About other options

Fatty acid (palimitoyl CoA) synthesis is increased in fed state. Fatty acids are synthesized from acetyl-CoA.
In fed state acetyl-CoA is oxidized via TCA cycle. Acetyl-CoA condenses with oxaloacetate to form citrate.
Oxalosuccinate is an intermediate of TCA cycle.


Question: Type of collagen forming basement membrane of kidney

Type IV collagen is abnormal, so basement membrane of kidney glomerular apparatus is abnormal. Hence, hematuria is seen, which will eventually progress to kidney failure.Ref: DM Vasudevan, page no: 583


Question: Long chain fatty acids penetrate the inner mitochondrial membrane as

Long-Chain Fatty Acids Penetrate the Inner Mitochondrial Membrane as Carnitine Derivatives Carnitine (-hydroxy--trimethylammonium butyrate), (CH3)3N+--CH2--CH(OH)--CH2--COO-, is widely distributed and is paicularly abundant in muscle. Long-chain acyl-CoA (or FFA) cannot penetrate the inner membrane of mitochondria. In the presence of carnitine, however, carnitine palmitoyltransferase-I, located in the outer mitochondrial membrane, conves long-chain acyl-CoA to acylcarnitine, which is able to penetrate the inner membrane and gain access to the -oxidation system of enzymes. Carnitine-acylcarnitine translocase acts as an inner membrane exchange transpoer. Acylcarnitine is transpoed in, coupled with the transpo out of one molecule of carnitine. The acylcarnitine then reacts with CoA, catalyzed by carnitine palmitoyltransferase-II, located on the inside of the inner membrane, reforming acyl-CoA in the mitochondrial matrix, and carnitine is liberated. Ref: Biochemistry by U. Satyanarayana 3rd edition Pgno : 288


Question: Active moiety of CoA is

- Synthesis of coenzyme A from pantothenate occurs in a series of  reactions. Pantothenate is  first phosphorylated to  which  cysteine is  added. Decarboxylation, followed by addition of AMP moiety and a phosphate (each from ATP) results in  coenzyme A.
-Coenzyme A serves as a carrier of activated acetyl or acyl groups (as thiol esters).


Question: Difference between reversible and irreversible reaction is


Question: Cyclic AMP increase the rate of glycogenolysis by

The roles of cAMP and inorganic phosphate (Pi) in the regulation of muscle glycogenolysis during exercise have been investigated in humans using the needle biopsy technique. The fraction of phosphorylase a in resting muscle was as a mean 23%, but the rate of glycogenolysis was extremely low. Epinephrine infusion increased cAMP in muscle by 3-fold and transformed 80% of phosphorylase to the form

Promoting the formation of phosphorylase

Acting as a cofactor for glycogen phosphorylase

Furnishing phosphate for the phosphorylysis of glycogen

Acting as a precursor of 5' AMP which is a cofactor for glycogen phosphorylase


Question: Movement of protein from nucleus to cytoplasm can be seen by

B i.e. FRAPFRAP (fluorescence recovery after photobleaching) primarily measures rate of lateral diffusion of lipids and it can be used to investigate diffusion of biological macromolecules (such as proteins etc) including lateral diffusion in the plane of membrane and movements into & out of nucleus.- FRET is used to visualize biochemistry of living cells such as to measure cAMP and activity of PKA.AFM (atomic force microscopy) is used to yield 3D contour map of membrane (surfaces) and visualize membrane proteins (eg microdomains or rafts etc)


Question:
Ligand for peroxisome proliferation activating receptor (PPAR), a group of nuclear hormone receptors that are involved in the regulation of genes related to glucose and lipid
metabolism is


Question: Not present in DNA


Question: Hexokinase is a

The International Union of Biochemistry (IUB) name of hexokinase is ATP:D-hexose 6-phosphotransferase E.C. 2.7.1.1. This name identifies hexokinaseas a member of class 2 (transferases), subclass 7 (transfer of a phosphoryl group), sub-subclass 1 (alcohol is the phosphoryl acceptor), and "hexose-6" indicates that the alcohol phosphorylated is on carbon six of a hexose.Ref: Harper&;s Biochemistry; 30th edition; Chapter 7; Enzymes: Mechanism of Action


Question: Gaucher's disease is due to enzyme deficiency of

(A) Glucocerebrosidase# Gaucher disease refers to a duster of autosomal recessive disorders resulting from mutations in the gene encoding glucocerebrosidase. This disease is the most common lysosomal storage disorder.> This affected gene encodes glucocerebrosidase, an enzyme that normally cleaves glucose residue from ceramide> As a result, glucocerebroside accumulates principally in the phagocytic cells of the body but in some forms also in the central nervous system.> Glucocerebrosides derived mainly from the cell membranes of leukocytes and erythrocytes.


Question: Sulfur of cysteineare not used/ utilized in the body for the following process/product

Methionine is an essential amino acid, so it cannot besynthesized from Cysteine.- But Sulfur of cysteine is donated by sulfur ofmethionine.- This is called transsulfuration reaction.- PLP is the coenzyme of transrulfuration.- The reaction is catalyzed by Cystathionine betaSynthase and Cystathionase enzyme

Help in the conversion of cyanide to thiocyanate

Disulfide bond formation between two adjacent peptide.


Question: Lipoprotein involved in reverse cholesterol transpo is

The class B scavenger receptor B1 (SR-B1) has been identified as an HDL receptor with a dual role in HDL metabolism. In the liver and in steroidogenic tissues, it binds HDL apo A-I, and cholesteryl ester is selectively delivered to the cells, although the paicle itself, including apo A-I, is not taken up. In the tissues, on the other hand, SR-B1 mediates the acceptance of cholesterol effluxed from the cells by HDL, which then transpos it to the liver for excretion the bile (either as cholesterol or after conversion to bile acids) in the process known as reverse cholesterol transpo. Reference: Harper; 30th edition; Page no: 259


Question: Binds to the receptors on Leydig cells.

LH binds to the receptors on Leydig cells and stimulates the release of testosterone. PRL, TSH, GH, and FSH do not bind to Leydig cells.


Question: Thin limbs, central obesity, fat cheeks, a ruddy complexion, and an elevated blood glucose level.

Excess production of cortisol causes muscle breakdown (hence thin limbs), fat deposition in the face and abdomen, thin skin (due to protein breakdown), and an increase in red blood cells, resulting in a red complexion. Blood glucose levels are elevated because cortisol stimulates gluconeogenesis. These symptoms do not appear due to elevated renin, aldosterone, PRL, or GH levels.

Elevated blood levels of aldosterone and renin resulting from an atherosclerotic plaque in a renal artery.

Hyperprolactinemia due to a pituitary tumor.

Acromegaly due to a GH-producing tumor that developed in adulthood.

Cushing syndrome due to an adrenal tumor.


Question: Defect in lipoprotein lipase enzyme leads to

Defect in either lipoprotein lipase or its cofactor Apo C II leads to Type I hyperlipoproteinemia chylomicrons, VLDL gets elevated in the body.


Question: Enzyme deficiency in McArdle syndrome

Glycogen storage disorderTypeNameEnzyme DeficiencyClinical FeaturesType VMyophosphorylase deficiency,McArdle syndromeMuscle phosphorylasePoor exercise tolerance; muscle glycogen abnormally high(2.5%-4%); blood lactate very low after exerciseRef: Harper&;s Biochemistry; 30th edition; Table 18-2; Chapter 18; Metabolism of Glycogen


Question: One molecule of Hb can bind to a maximum number of

Hemoglobins bind four molecules of O2 per tetramer, one per heme. A molecule of O2 binds to a hemoglobin tetramer more readily if other O2 molecules are already bound.Reference: Harper&;s Biochemistry; 30th edition; Chapter 6; Proteins: Myoglobin & Hemoglobin


Question: Melatonin is synthesized from

Ans. c (Tryptophan). (Ref. Harper, Biochemistry, 25th /pg.355)AMINOACID DERIVATIVESPhenylalanine:# Phenylalanine >> tyrosine >> dopa >> norepinephrine >> epinephrine# Phenylalanine >> tyrosine >> dopa >> dopamine >> melanin2# Phenylalanine >> tyrosine >> thyroxineTryptophan# Niacin# Serotonin# Melatonin2Histidine# Histidine -Histamine (by decarboxylation)Glycine# Porphyrin and haeme# Purines# Creatine (totally madeup of glycine + arginine + methionine; mnemonic--GAM)# Glutathione (totally made up of glycine + cystine+ glutamate; mnemonic--GCG)Arginine# Carnitine# UreaMethionine# Choline


Question: Ubiquitin is involved in

In animals, many proteins are degraded by the ubiquitin- protease pathway. This pathway was discovered by Aaron Ciechanover, A Hershko and Irwin Roose who got Nobel Prize. Proteosome 26s Protein * Comprises more than 30 polypeptide subunits, which are arranged in the form of a hollow cylinder. * Active sites of its proteolytic subunits face the interior of the cylinder, thus preventing the indiscriminate degradation of cellular proteins. * Proteins requiring degradation are targeted to the proteasome by "Ubiquitination"--the process in which there is covalent attachment of one or more ubiquitin molecules. Ubiquitin: It is a small, approximately 7s residue protein that is highly conserved among eukaryotes. Ubiquitination: It is catalyzed by a large family of enzymes called "E3 Ligases", which attach ubiquitin to the side chain amino group of lysyl residues.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 131


Question: Carbamoyl phosphate is used in

One molecule of ammonia and co2 condenses to form Carbomy phoshate in presence of 2 molecules of ATP and carbomyl phosphate synthetase II enzyme. this carbomyl phoshate is transferred to NH2 group of ornitine to form Citrulline in urea cycle.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 203


Question: Trans fatty acids are known to form during

Trans fatty acids (TFA) are atherogenic. They lower the HDL level and elevate LDL level. TFA is present in dairy products and hydrogenated edible oils. It is widely used in the food industry since it increases the shelf life of fried food. Cooking media containing PUFA and fast food preparations have a high content of trans fatty acids. Trans fatty acids adversely affect endothelial function and aggravate insulin resistance and diabetes. It is high in processed foods and bakery products, where hydrogenated vegetable oils are used for cooking.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 437


Question: Sulphur containing bond is not found in

Hyaluronic Acid A sulfate-free mucopolysaccharide. It was first isolated from the vitreous humor of the eye. Later it was found to be present in synol fluid, skin, umbilical cord, haemolytic streptococci and in the rheumatic nodule. It occurs both free and salt-like combination with proteins and forms so-called ground substance of mesenchyme, an integral pa of the gel-like ground substance of connective and other tissues. Composition: It is composed of repeating units of N-acetyl glucosamine and D-Glucuronic acid. On hydrolysis, it yields equimolecular quantities of D-Glucosamine, D-Glucoronic acid and acetic acid (Fig. 3.20). Functions: (See below under proteoglycans) Hyaluronidase: An enzyme present in ceain tissues, notably testicular tissue and spleen, as well as in several types of pneumococci and haemolytic streptococci. The enzyme catalyzes the depolymerization of hyaluronic acid and by reducing its viscosity facilitates diffusion of materials into tissue spaces. Hence the enzyme, sometimes, is designated as spreading factor.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 34


Question: In starvation, nitrogen is carried from muscle to liver and kidney by

Transport of alanine from muscle to liver (glucose-alanine cycle) has two functions :-

Providing substrate for gluconeogenesis
Transport of ammonia (NH4+) to liver for urea synthesis


Question: The reducing equivalents for cholesterol biosynthesis are provided by

Cholesterol is a 27-carbon compound consisting of 4 rings and a side chain. It is synthesized from acetyl-CoA by a lengthy pathway that may be divided into five steps:(1) synthesis of mevalonate from acetyl-CoA (2) formation of isoprenoid units from mevalonate by a loss of CO2 (3) condensation of six isoprenoid unitsform squalene (4) cyclization of squalene gives rise to the parent steroid, lanosterol; (5) formation of cholesterol from lanosterol.NADPH provides the reducing equivalents.Ref: Harper&;s Biochemistry; 30th edition; Chapter 26; Cholesterol Synthesis, Transpo, & Excretion


Question: Albumin is exclusively synthesized by

Total serum protein and albumin Measure of the biosynthetic function of the liver, as the liver is the primary site of synthesis of most plasma proteins. Roughly 70% to 80% of all plasma proteins are synthesized in the liver. These include albumin, fibrinogen, transferrin, and most components of the complement and blood coagulation cascade with the exception of von Willebrand factor, which is synthesized in the vascular endothelium. Ref: Biochemistry by U. Satyanarayana 3rd edition Pgno : 183


Question: Drug detoxification and steroid synthesis occur in


Question: "Type I phenylketonuria" is caused by a deficiency of

Hyperphenylalaninemias arise from defects in phenylalanine hydroxylase, EC 1.14.16.1 (type I, classic phenylketonuria (PKU), frequency 1 in 10,000 bihs), in dihydrobiopterin reductase (types II and III), or in dihydrobiopterin biosynthesis (types IV and V).Ref: Harper&;s Biochemistry; 30th edition; Chapter 29 Catabolism of the Carbon Skeletons of Amino Acids


Question: Splicing is a process of

Removal of Introns : The primary transcripts are very long ;they have molecular weights more than 10 power of 7.Molecular weight of mature mRNA is about 1-2 x 10 power of 6.This means large poion of hnRNA are cleaved off. The primary transcript contains coding regions (exons)interspersed with non-coding regions (introns). These intron sequences are cleaved and the exons are spliced (combined together ) to orm the mature mRNA molecule.This processing is done in the nucleus.Splicing is an energy requiring process. REF :DM VASUDEVAN TEXTBOOK ;7th EDITION ; Page no :591.


Question: Transfer of a poion of the DNA from one bacterium to another by bacteriophage is known as


Question: In the Krebs cycle, Malonate competitively inhibits

The first dehydrogenation reaction, forming fumarate, is catalyzed by succinate dehydrogenase, which is bound to the inner surface of the inner mitochondrial membrane. The enzyme contains FAD and iron-sulfur (Fe-S) protein, and directly reduces ubiquinone in the electron transpo chain. This is inhibited by Malonate Reference: Harper; 30th edition; Page no: 163


Question: Glutamine replaced by valine in sickle cell anaemia is characterized by


Question: Most impoant tool used in genetic engineering

Ans. is 'b' i.e., Enzymes Genetic engineering simply means manipulation of genetic material to achieve the desired goal in a predetermined way.Most impoant molecular tools in genetic engineering are enzymes used in recombinant DNA technology. (also called genetic engineering).Most impoant of these enzymes is restriction endonuclease.


Question: PIN number of oxygen is

Ans: a (2,5 ) Ref: Ajay Yadov, 2nded, p. 22Pin index for gasesOxygen-2,5 Entonox(50%02 +50%N2O)-7Nitrous oxide-3,5 Carbondioxide(<7.5%)-2,6Cyclopropane-3,6 Carbondioxide(> 7.5%)-1,6Air-1,5 Nitrogen-1,4


Question: Arginosuccinate is synthesized from

Ans. is 'c' i.e., Citrulline and aspaate Arginosuccinate is synthesized from citrulline and aspaate in Urea cycle.


Question: The enzymes level used for evaluation of myopathies is

Clinical suspicion for a myopathy is high, generally corroborated by elevated creatine kinase (CK) levels, it is often reasonable to skip or limit the extent of the EDX studies. Finally, EDX studies may be normal in selected muscle diseases (ceain endocrine, metabolic, congenital, and mitochondrial myopathies). Thus, in the appropriate clinical context, normal EDX studies do not necessarily rule out the presence of a myopathy.


Question: Cholesterol is transpoed to aerial smooth muscle by

Ref: Textbook of Medical Biochemistry 8th Edition Dr (Brig) MN Chatterjea, Rana Shinde, page no: 434,435


Question: Unfolded proteins are handled by

Abnormal folding of proteins may lead to prion diseases. Chaperones help to produce the correct spatial arrangement. Chaperones attach to nascent polypeptide chains and prevent wrong foldings so that folding is allowed only in the correct direction.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 604


Question: Molecular change in Lysosomal storage disorder is

Mutation(s) in a gene encoding a lysosomal hydrolase involved in the degradation of one or more GAGsAccumulation of substrate in various tissues, including liver, spleen, bone, skin, and central nervous systemDefective lysosomal hydrolaseThe metabolic block, as in the case of the mucolipidoses.Hyaluronidase is one impoant enzyme involved in the catabolism of both hyaluronic acid and chondroitin sulfate. It is a widely distributed endoglycosidase thatcleaves hexosaminidase linkages.From hyaluronic acid, the enzyme will generate a tetrasaccharide with the structure (GlcUAb-1,3-GlcNAc-b-1,4)2, which can be degraded fuher by a b-glucuronidase and b-N-acetylhexosaminidase.A genetic defect in hyaluronidase causes MPS IX, a lysosomal storage disorder in which hyaluronic acid accumulates in the joints

Defective fusion of lysosomes and phagosomes

Mutation of genes encoding lysosomal hydrolases


Question: After overnight fasting, levels of Glucose transporters are reduced in

Overnight fasting causes insulin levels to fall. This decreases the number of glucose transporters which are insulin dependent.
Insulin-dependent glucose transporters are GLUT-4, present in adipocytes, skeletal and cardiac muscles. Rest of the glucose transporters are not insulin dependent.


Question: Cholesterol is a (an)

Sterol

Cholesterol is the most important sterol.


Question: In Kreb's cycle and Urea cycle the linking component is

Urea cycle * Cleavage of argininosuccinate by argininosuccinate lyase, results in formation of arginine and release of the aspaate skeleton as fumarate (funnelled into TCA cycle) * Subsequent addition of water to fumarate forms l-malate, with subsequent oxidation forms oxaloacetate, followed by its transamination by glutamate aminotransferase then re-forms aspaate. * Argininosuccinate synthase links aspaate and citrulline forms argininosuccinate. * Thus the urea cycle is linked to TCA cycle through fumarate Ref:- Harper 30/e; pg num:- 294


Question: Enzymes of Calvin cycle are

The Calvin cycle is regulated by light-dependent activation of at least 5 enzymes: Rubisco(Ribulose Bisphosphate Carboxylase) NADP:glyceraldehyde-3-phosphate dehydrogenase Fructose-1,6-bisphosphate phosphatase Sedoheptulose-1,7-bisphosphate phosphatase Ribulose-5-phosphate kinase Of these 5 enzymes, all except rubisco are regulated by the ferredoxin-thioredoxin system. REF:DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, EIGHTH EDITION,PG.NO.,304.


Question: Enzymes involved in PUFA synthesis

The biosynthesis of PUFAs involves the introduction of double bonds (desaturation) in the aliphatic chain of a fatty acid and the extension (elongation) by two carbon units, of the acyl chain. So, the biosynthetic pathway involves the alternate action of enzymes currently named desaturases and elongases. Fatty acid substrates are always in the form of thioesters of acyl carrier proteins (ACP), Coenzyme A (CoA) or esterified to phospholipidsDesaturation is an aerobic process utilizing molecular oxygen and reducing equivalents obtained from an electron transpo chain.The electron donor depends only on the subcellular location of the desaturase, being cytochrome b5 in the endoplasmic reticulum and ferredoxin in plastids and bacteria.Desaturases represent a complex group of enzymes that could be classified in different ways, depending on the kind of esterification of the fatty acid used as substrate; the solubility of the enzyme; the electron donor; subcellular localization and the regioselectivity of the reaction.


Question: The gaps between segments of DNA on the lagging strand produced by restriction enzymes are rejoined/sealed by

In molecular biology, DNA ligase is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formationHelicase action in DNA replication. Helicases are often used to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases.Topoisomerases are enzymes that paicipate in the overwinding or underwinding of DNAPhosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate


Question: Number of structural genes in Lac operon is

The structural gene for b-galactosidase (lacZ) is clustered with the genes responsible for the permeation of lactose into the cell (lacY) and for thiogalactoside transacetylase (lacA). The structural genes for these three enzymes, along with the lac promoter and lac operator (a regulatory region), are physically associated to constitute the lac operonRef: Harper 27e, page: 430


Question: High energy compound is

Adenosine Triphosphate (ATP) i. ATP is the universal currency of energy within the living cells. Structure of ATP is shown in Figure 5.3. ii. The hydrolysis of ATP to ADP (under standard conditions) releases -30.5 kJ/mol or-7.3 kcal/mol (DG0' = - 7.3). The energy in the ATP is used to drive all endergonic (biosynthetic) reactions. The energy efficiency of the cell is comparable to any machine so far invented. ATP captures the chemical energy released by the combustion of nutrients and transfers it to synthetic reactions that require energy. iii. At rest, Na+-K+ -ATPase (see Chapter 2) uses up one-third of all ATP formed. Other energy requiring processes are, biosynthesis of macromolecules, muscle contractions, cellular motion using kinesin, dynein, etc. iv. ATP is continually being hydrolyzed and regenerated. An average person at rest consumes and regenerates ATP at a rate of approximately 3 molecules per second, i.e. about 1.5 kg/ day!Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 226


Question: In Eukaryotes, mRNA is produced by

There is only 1 RNA polymerase in prokaryotes. There are 3 eukaryotic RNA polymerases Type Location RNA transcribed Effect of a-amanitin I Nucleolous 18, 5.8, 28 rRNA Insensitive II Nucleoplasm mRNA, miRNA, snRNA Highly sensitive III Nucleoplasm tRNA, 5s rRNA , U6 snRNA Less sensitive


Question: The immediate precursor of mevalonic acid is

Beta-hydroxy beta-methyl glutaryl CoA (HMG CoA). The reduction of HMG CoA to mevalonate is catalysed by HMG CoA reductase. It is a microsomal (endoplasmic reticulum) enzyme.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 148


Question: Enzyme deficiency in Tarui disease is

Type name Enzyme Deficiency Clinical Features VII Tarui disease Muscle and erythrocyte phosphofructokinase 1 Poor exercise tolerance Muscle glycogen abnormally high (2.5%-4%) Blood lactate very low after exercise Also hemolytic anemia Reference: Harper; 30th edition; Table: 18-2; Page no: 179


Question: Transcription is inhibited by

Clindamycin -D antibiotics from StreptomycesMode of action is by inseion of phenoxa-zone ring between two G-C bp of DNA USed as anti-cancer drugRef: DM Vasudevan, 7th edition, page no: 593 table 45.2


Question: Optical transmission through a solution depends on

The amount of light that passes through a laboratory specimen. It can be used to measure the concentration of componentsin the specimen (e.g., the amount of solute contained in a solution).Ref: Textbook of Medical Biochemistry, D M VASUDEVAN


Question: Unwinding of DNA is done by

In addition to binding to the nucleosome, the H1 protein binds to the "linker DNA" (approximately 20-80 nucleotides in length) region between nucleosomes, helping stabilize the zig-zagged 30 nm chromatin fiber Ref-Sathyanarayana 4/e p360


Question: NAD+ linked dehydrogenase is

Pyruvate Dehydrogenase Complex - Inside the mitochondria, pyruvate is oxidatively decarboxylated to acetyl CoA by pyruvate dehydrogenase (PDH). It is a multi-enzyme complex with 5 co-enzymes and 3 apo-enzymes. The coenzymes needed are: Thiamine pyrophosphate (TPP) Co-enzyme A (CoA) FAD NAD+ Lipoamide. The lipoic acid, otherwise called thioctic acid has two sulphur atoms and 8 carbon atoms. It can accept or donate hydrogen atoms. 6. The enzyme pa of the PDH complex is made up of three component enzymes. 6-A. Pyruvate Dehydrogenase (Enzyme 1): It catalyses oxidative decarboxylation. TPP is required in this step. So, Thiamine, a B-complex group vitamin is essential for utilization of pyruvate.An enzyme bound hydroxylethyl TPP is formed. 6-B. Dihydro Lipoyl Trans Acetylase (Enzyme 2): Then, hydroxyethyl group is oxidized to form an acetyl group and then transferred from TPP to lipoamide to form acetyl lipoamide. 6-C. Dihydro Lipoyl Dehydrogenase (Enzyme 3): The last step is the oxidation of lipoamide. At the end of the reaction the cofactors, namely TPP, Lipoamide and FAD are regenerated. REF: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY,EIGHTH EDITION,PG.NO.,135.


Question: Cofactor for lipoprotein lipase is

Both phospholipids and apo C-II are required as cofactors for lipoprotein lipase activity, while apo A-II and apo C-III act as inhibitors. Reference: Harper; 30th edition; Page no: 257


Question: The main function of Vitamin C in the body is

Vitamin C is one of a group of nutrients that includes vitamin E (see p. 391) and b-carotene (see p. 382), which are known as antioxidants. Consumption of diets rich in these compounds is associated with a decreased incidence of some chronic diseases, such as coronary hea disease and ceain cancers. However, clinical trials involving supplementation with the isolated antioxidants have failed to determine any convincing beneficial effects.Reference: Lippincott, Edition 5, page no: 378


Question: UAC to UAG

UAC, a tyrosine can be mutated to a termination codon, UAA or UAG. This leads to premature termination of the protein, and so functional activity may be destroyed. This process is called nonsense or terminator codon mutation. Frameshift mutation is due to addition or deletion of bases. Missense mutation is due to a change in amino acid may be produced in the protein. These are the effects of mutation, whereas deletion, substitution, inseion are classification of mutation.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 613


Question: Dietary cholesterol is transported to extrahepatic tissue by

LDL

It is worth noting that dietary cholesterol is not directly transported to extrahepatic tissues.
Though the major function of chylomicrons is to transport exogenous triglyceride to various tissues, it also transports the other dietary lipids (including cholesterol) to the liver after conversion into chylomicron remnants.
In the liver, this dietary cholesterol and the endogenous cholesterol which is synthesized in the liver itself are incorporated into VLDL which is secreted into the circulation. In circulation, VLDL is converted to IDL and then to LDL. This LDL serves to deliver the cholesterol to various extrahepatic tissues. Thus, LDL transport dietary as well as endogenous cholesterol to extrahepatic tissues.


Question: Cytochrome Oxidase is a

Cytochrome oxidase is a hemoprotein widely distributed in many tissues, having the typical heme prosthetic group present in myoglobin, hemoglobin, and other cytochromes.Ref: Harper Biochemistry; 30th edition; Chapter 12; Biologic Oxidation


Question: Gaucher's disease is due to deficiency of enzyme


Question: Fructokinase is necessary for production of

Fructose-1-PO4

Fructokinase is necessary for the production of fructose- 1 -phosphate from fructose.


Question: The energy source reserved for strenuous muscular activity

Muscle glycogen is used for energy during exercise. The glycogen is degraded to a form of glucose that can enter metabolic pathways for energy generation. Because exercise is strenuous, muscle requires large amounts of energy, and this can be generated at the fastest rate by converting muscle glycogen to pathway precursors within the muscle. Liver glycogen will produce glucose that enters the circulation. Once in the circulation, the muscle can take up that glucose and use it to generate energy; however, the rate of energy generation from liver-derived glucose is much slower than that from muscle-derived glucose.


Question: Blood samples for glucose estimation are collected in fluoride bulbs/tubes as fluride prevents glycolysis byinhibition of

Ans. a (Enolase) (Ref. Harper's Illustrated 26th ed., 137; 27th/Ch. 18)ENOLASE# The step of glycolysis catalyzed by enolase involves dehydration, forming phosphoenolpyruvate.# Enolase is inhibited by fluoride.- To prevent glycolysis in the estimation of glucose, blood is collected in tubes containing fluoride.# The enzyme is also dependent on the presence of either Mg2+ or Mn2+.# The phosphate of phosphoenolpyruvate is transferred to ADP by pyruvate kinase to generate, at this stage, two molecules of ATP per molecule of glucose oxidized.# The product of the enzyme-catalyzed reaction, enolpyruvate, undergoes spontaneous (nonenzymic) isomerization to pyruvate and so is not available to undergo the reverse reaction.# The pyruvate kinase reaction is thus also irreversible under physiologic conditions. EnzymeInhibitorPathway1.AconitaseFluoroacetateKrebs cycle2.L-KG dehydrogenaseArseniteKrebs cycle3.EnolaseFluorideGlycolysis4.Succinate dehydrogenaseMalonate oxaloacetateKrebs cycle5.Glyceradehyde-3 phosphateLactoacetate dehydrogenaseGlycolysis6.MOAIproniazid 7.Pyruvate dehydrogenaseArsenite 8.Carbonic anhydraseSulfanilamide


Question: Protein targeted for destruction in eukaryotes are covalently linked to

Ubiquitin plays a major role in the degradation of proteins and is particularly associated with the disposal of misfolded proteins.
It is a small, highly conserved protein that plays a key role in marking various proteins for subsequent degradation in proteosomes.


Question: Detoxification of drugs is controlled by;

Ans B. Cytochrome P450 Detoxification is the removal of toxic substances from the body. Metabolism of xenobiotics takes place in two phases. In phase 1, the major reaction involved is hydroxylation, catalyzed by members of a class of enzymes referred to as monooxygenases or cytochrome P450s . The reaction catalyzed by a monooxygenase (cytochrome P450 ) is as follows:RH+O+NADPH+H+-ROH+HO+NADPRH above can represent a very wide variety of xenobiotics, including drugs, carcinogens, pesticides, petroleum products, and pollutants (such as a mixture of PCBs). In addition, endogenous compounds, such as certain steroids, eicosanoids, fatty acids, and retinoids, are also substrates. The substrates are generally lipophilic and are rendered more hydrophilic by hydroxylation. Cytochrome P450 is considered the most versatile biocatalyst known.


Question: Most impoant enzyme in DNA replication for chain elongation

Ans. is 'c' i.e.,DNA polymerase III Impoant DNA PolymerasesIn ProkaryotesDNA polymerase I :- Helps in gap filling and synthesis between okazaki fragments of lagging strand, and replaces ribonucleotides of RNA primer by deoxyribonucleotides. It has (i) 3' 5' exonuclease activity, (ii) 5' 3' exonuclease activity and (iii) polymerase (5' -> 3' polymerase) activityDNA polymerase II:- Helps in (i) proof reading (3' 5' exonuclease activity), and (ii) DNA repair.DNA polymerase III :- It is the main enzyme that synthesizes prokaryote DNA, i.e., synthesis of leading and lagging strand. It has (i) 5' -> 3' polymerase (or simply polymerase) activity for DNA synthesis, and (ii) 3'->5' exonuclease activity for proof reading.In EukaryotesDNA polymerase a :- It has primase activity (i.e. synthesizes RNA primer), and initiates DNA synthesis.DNA polymerase p :- It is a DNA repair enzymeDNA polymerase y :- Replicates mitochondrial DNADNA polymerase ?:- Helps DNA synthesis on lagging strand, i.e. elongation of okazaki fragments on lagging strand. It also has 5'->3' exonuclease activity for proof reading.DNA polymerase c :- Helps in DNA synthesis on leading strand. It also has 5'43 'exonuclease activity for proof reading.


Question: "Transition mutation" occurs in

Replacement of purine by another purine (A to G or G to A ) or pyrimidine by pyrimidine (T to C or C to T ) is called transition mutationRef: DM Vasudevan, 7th edition, page no: 612


Question: Proteins are separated on the basis of size by

The most widely used method for determining the purity of a protein is SDS - PAGE - Poly-acryl-amide gel-electrophoresis (PAGE) in the presence of the anionic detergent sodium dodecyl sulfate (SDS). Electrophoresis separates charged bio-molecules based on the rates at which they migrate in an applied electrical field.Since the charge-to-mass ratio of each SDS polypeptide complex is approximately equal, the physical resistance each peptide encounters as it moves through the acrylamide matrix determines the rate of migration. Since large complexes encounter greater resistance, polypeptides separate based on their relative molecular mass (M), Individual polypeptides trapped in the acrylamide gel are visualized by staining with dyes such as Coomassie blue.Ref: Harper 28th Ed. Page-23, Harper 27th Ed. Page: 24


Question: Complementary RNA sequence of 5&; AGTCTGACT3&;

Adenine complementary to uracil in RNA Guanine complementary to cytosineRef: DM Vasudevan, 7th edition, page no: 457


Question: Codons are present in

A triplet sequence of nucleotides on the mRNA is the coson for each amino acid. The codons are on the mRNA. Each codon is a consecutive sequence of three bases on the mRNA , Eg : UUU codes for phenylalanine. Reference : DM.VASUDEVAN.TEXTBOOK SEVENTH EDITION ; PAGE NO : 598


Question: Amobarbital inhibit electron transpo

Barbiturates such as amobarbital inhibit electron transpo Complex I by blocking the transfer from Fe-S to Q. At sufficient dosage, they are fatal in vivo. Reference: Harper; 30th edition; Page no: 132


Question: NADPH+ is generated in the reaction catalysed by

Amongst the given options, only G6-PD (glucose-6-phosphate dehydrogenase) is NADP linked enzyme.
NAD+ -linked dehydrogenases: Pyruvate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase. α -ketoglutarate dehydrogenase, glutamate dehydrogenase, glyceraldehyde-3-P dehydrogenase, lactate dehydrogenase, β -hydroxy acyl CoA dehydrogenase, glycerol 3-P dehydrogenase (cytoplasmic).

NADP+-linked dehydrogenases :Glucose-6-P dehydrogenase, 6-Phosphogluconate dehydrogenase, 3-ketoacyl reductase, Enoyl reductase.

FAD-linked dehydrogenases: Succinate dehydrogenase, fatty acyl CoA dehydrogenase, glycerol-3P dehydrogenase (mitochondrial).


Question: Sickling in 'HbS' disease is primarily caused by


Question: Benedict test is for

It is commonly employed to detect the presence of glucose in urine. Benedict&;s reagent contains sodium carbonate, copper sulfate, and sodium citrate. In alkalain medium, sugars form enediol, cupric ions are reduced, correspondingly sugar is oxidized. Glucose is a reducing sugar. Any sugar with free aldehyde/keto group will reduce Benedict&;s reagent.Ref: DM Vasudevan, 7th edition, page no: 73


Question: Most important in causing coronary artery disease (CAD) is

LDL

LDL concentration in blood has a positive correlation with the incidence of cardiovascular diseases.
LDL-cholesterol is deposited in vessels and promotes atherosclerosis.
Therefore, LDL is called 'bad cholesterol' or 'lethally dangerous lipoprotein (LDL)'.


Question: Chain initiation in protein synthesis is by

Initiation codon AUG codes for methionine.


Question: Orotic aciduria is due to deficiency of

Orotic aciduria an autosomal recessive disorder, can be caused by a deficiency in the enzyme UMPS, a bifunctional protein that includes the enzyme activities of orotate phosphoribosyltransferase and orotidine 5'-phosphate decarboxylase.


Question: Acetyl CoA carboxylase is activated by

Citrate

Acetyl-CoA carboxylase is an allosteric enzyme, it is activated by citrate and inhibited by long-chain acyl-CoA (palmitoyl CoA).


Question: Nucleosomes are

Nucleosomes : The double stranded DNA wraps twice around a histone octamer formed by H2A, H2B, H3 and H4. This super - twisted helix forms a spherical paicle of 10nm diameter ; called Nucleosome. The function of the Nucleosomes is to condense DNA ; this arrangement also stabilises the DNA. REF : DM.VASUDEVAN.TEXTBOOK; SEVENTH EDITION ; PAGE NO :577


Question: Biotin is required for the activity of

Mitochondrial pyruvate carboxylase catalyzes the carboxylation of pyruvate to oxaloacetate, an ATP-  requiring reaction in which the vitamin biotin is the coenzyme.
Biotin binds CO2 from bicarbonate as carboxybiotin prior to the addition of the CO2 to pyruvate.
The resultant oxaloacetate is reduced to malate, exported from the mitochondrion into the cytosol  and there oxidized back to oxaloacetate.

Key Concept:
Biotin is the co-enzyme for pyruvate carboxylase which carboxylates pyruvate into oxaloacetate
Ref : Harper’s illustrated biochemistry, 31st edition.


Question: Pyrimidine metabolism features a/e

D i.e. Reye syndrome decrease cytosolic carbamoyl phosphate


Question: Cardiolipin is found in

Phosphatidyl Glycerol It is formed by esterification of phosphatidic acid to glycerol. When two molecules of phosphatidic acid are linked with a molecule of glycerol, phosphatidyl glycerol or cardiolipin is formed. It is the major lipid of mitochondrial membrane. Commercially, it is extracted from the myocardium. Decreased cardiolipin level leads to mitochondrial dysfunction, and is accounted for hea failure, hypothyroidism and some types of myopathies.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 81


Question: Beta oxidation of fatty acids occur in

Tissues in which bbb-Oxidation is carried out: The circulating FA are taken up by various tissues and oxidised. Tissues like liver, hea, kidney, muscle, brain, lungs, testes and adipose tissue have the ability to oxidise long-chain FA. In cardiac muscle, fatty acids are an impoant fuel of respiration (80% of energy derived from FA oxidation). Enzymes Involved in bbb-Oxidation bbb-oxidation takes place in mitochondrion. Several enzymes known collectively as FA-oxidase system are found in the mitochondrial matrix, adjacent to the respiratory chain, which is found in the inner membrane. These enzymes catalyse the oxidation of FA to acetyl- CoA.Ref: Textbook of Medical Biochemistry, Eighth Edition, Dr (Brig) MN Chatterjea, page no: 407


Question: Sickling in 'Hbs' disease is primaily caused by

The primary pathophysiological event in sickling is intracellular polymerization of deoxy-HbS due to its markedly reduced solubility.


Question: Beta alanine is a end product of


Question: Bile acids are formed from


Question: Increased blood levels of cholesterol that are seen in hypothyroidism are most likely due to

Thyroid hormones induce the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which is the first step in cholesterol biosynthesis.Moreover, triiodothyronine (T3) upregulates LDL receptors by controlling the LDL receptor gene activation. This T3-mediated gene activation is done by the direct binding of T3 to specific thyroid hormone-responsive elementsFuhermore, T3 controls the sterol regulatory element-binding protein-2 (SREBP-2), which in turn regulates LDL receptor's gene expression Ref: DM Vasudevan, 7th edition, page no: 336, 334, 676

Decreased production of LDL receptor in liver and the thus decreased clearance by liver

Decreased production of LDL receptor in the adipose tissue and increases release of cholesterol from adipose tissues

Increased breakdown of lipoproteins releasing releasing cholesterol in circulation


Question: Professional antigen presenting cells

Antigen-presenting cells fall into two categories: professional and non-professional. Those that express MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors are often called professional antigen-presenting cells. The non-professional APCs express MHC class I molecules.An antigen-presenting cell (APC) or accessory cell is a cell that displays antigen complexed with major histocompatibility complexes (MHCs) on their surfaces; this process is known as antigen presentation. T cells may recognize these complexes using their T cell receptors (TCRs). These cells process antigens and present them to T-cells. Professional antigen-presenting cells, including macrophages, B cells and dendritic cells, present foreign antigens to helper T cells, while other cell types can present antigens originating inside the cell to cytotoxic T cells. In addition to the MHC family of proteins, antigen presentation relies on other specialized signalling molecules on the surfaces of both APCs and T cells.Dendritic cells (DC)Dendritic cells have the broadest range of antigen presentation and are necessary for activation of naive T cells. DCs present antigen to both helper and cytotoxic T cells. They can also perform cross-presentation, a process by which they present exogenous antigen on MHC class I molecules to cytotoxic T cells. Cross-presentation allows for the activation of these T cells. Dendritic cells also play a role in peripheral tolerance, which contributes to prevention of auto-immune disease.MacrophagesMacrophages can be stimulated by T cell secretion of interferon gamma. After this activation, macrophages are able to express MHC class II and co-stimulatory molecules, including the B7 complex and can, present phagocytosed peptide fragments to helper T cells. Activation can assist pathogen-infected macrophages in clearing the infection.B cellsB cells can internalize antigen that binds to their B cell receptor and presents it to helper T cells. Unlike T cells, B cells can recognize soluble antigen for which their B cell receptor is specific. They can then process the antigen and present peptides using MHC class II molecules. When a T helper cell with a TCR specific for that peptide binds, the B cell marker CD40 binds to CD40L on the T cell surface. When activated by a T cell, a B cell can undergo antibody isotype switching, affinity maturation, as well as the formation of memory cells.


Question: Immediate energy supply for muscle contraction

A Sprinter Uses Creatine Phosphate & Anaerobic Glycolysis to Make ATP, Whereas a Marathon Runner Uses Oxidative PhosphorylationCreatine Phosphate Constitutes a Major Energy Reserve in MuscleCreatine phosphate prevents the rapid depletion of ATP by providing a readily available high-energy phosphate that can be used to regenerate ATP from ADP.Creatine phosphate is formed from ATP and creatine at times when the muscle is relaxed and the demand for ATP is relatively low.The enzyme catalyzing the phosphorylation of creatine is creatine kinase (CK), a muscle-specific enzyme with clinical utility in the detection of acute or chronic diseases of muscle.Ref: Harper&;s biochemistry, 30th edition, page no: 676


Question: Transfer of an amino group from an amino acid to alpha keto acid is done by


Question: Menke's Kinky hair syndrome is due to defect in

Menke's kinky hair syndrome is due to mutation in ATP7A gene, leading defective copper transporter.


Question: tRNA molecules vary in length from

tRNA molecules vary in length from 74 to 95 nucleotides, like many other RNAs, are also generated by nuclear processing of a precursor molecule.Ref: Harper&;s Biochemistry; 30th edition; Chapter 34; Nucleic Acid Structure & Function