Question: ATP is generated in ETC by

ATP SYNTHASE (COMPLEX V) It is a protein assembly in the inner mitochondrial membrane. It is sometimes referred to as the 5th Complex (Figs 19.14 and 19.15). Proton pumping ATP synthase (otherwise called F1-Fo ATPase) is a multisubunit transmembrane protein. It has two functional units, named as F1 and Fo. It looks like a lollipop since the membrane-embedded Fo component and F1 are connected by a protein stalk. Fo Unit: The "o" is pronounced as "oh"; and not as "zero". The "o" stands for oligomycin, as Fo is inhibited by oligomycin. Fo unit spans inner mitochondrial membrane. It serves as a proton channel, through which protons enter into mitochondria (Fig.19.14). Fo unit has 4 polypeptide chains and is connected to F1. Fo is water-insoluble whereas F1 is a water-soluble peripheral membrane protein. F1 Unit: It projects into the matrix. It catalyses the ATP synthesis (Fig. 19.14). F1 unit has 9 polypeptide chains, (3 alpha, 3 beta, 1 gamma, 1 sigma, 1 epsilon). The alpha chains have binding sites for ATP and ADP and beta chains have catalytic sites. ATP synthesis requires Mg++ ions. Mechanism of ATP synthesis: Translocation of protons carried out by the Fo catalyses the formation of the phospho-anhydride bond of ATP by F1. Coupling of the dissipation of proton gradient with ATP synthesis (oxidative phosphorylation) is through the interaction of F1 and Fo.Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 232


Question: Maximum cholesterol is seen in

Ref: Textbook of Medical Biochemistry Dr (Brig) MN Chatterjea Rana Shinde, 8th Edition, page no: 446


Question: Monoprotic acid is

Formic acid can donate one H+, it is monoprotic.The acid equilibrium problems discussed so far have focused on a family of compounds known as monoprotic acids. Each of these acids has a single H+ ion, or proton, it can donate when it acts as a Brnsted acid. Hydrochloric acid (HCl), acetic acid (CH3CO2H or HOAc), nitric acid (HNO3), and benzoic acid (C6H5CO2H) are all monoprotic acids.Several impoant acids can be classified as polyprotic acids, which can lose more than one H+ ion when they act as Brnsted acids. Diprotic acids, such as sulfuric acid (H2SO4), carbonic acid (H2CO3), hydrogen sulfide (H2S), chromic acid (H2CrO4), and oxalic acid (H2C2O4) have two acidic hydrogen atomsTriprotic acids, such as phosphoric acid (H3PO4) and citric acid (C6H8O7), have three.


Question: Fidelity of protein translation depends on

In translation, proof reading of mRNA is done by Amino acyl- tRNA synthetase. Amino acyl t-RNA synthetase is responsible for fidelity (faithfulness) of protein translation.


Question: Location of Keratan sulfate 1 is

Keratan sulfate I was originally isolated from the cornea, while keratan sulfate II came from cailage. In the eye, they lie between collagen fibrils and play a critical role in corneal transparency. Changes in proteoglycan composition found in corneal scars disappear when the cornea heals. Reference: Harper&;s Biochemistry; 30th edition; Chapter 50; The Extracellular Matrix


Question: Most abundant collagen in body is

The collagen superfamily of proteins includes more than 25 collagen types, as well as additional proteins that have collagen-like domains. The three polypeptide a chains are held together by hydrogen bonds between the chains. Variations in the amino acid sequence of the a chains result in structural components that are about the same size (approximately 1,000 amino acids long), but with slightly different propeies. These a chains are combined to form the various types of collagen found in the tissues. For example, the most common collagen, type I, contains two chains called a1 and one chain called a2 (a12a2)Ref: Lippincott's Illustrated Reviews: Biochemistry Fifth Edition Page no: 41


Question: Oligosaccharide is


Question: Lipotropic factors are

Lipotropic Factors - They are required for the normal mobilisation of fat from liver. Therefore, deficiency of these factors may result in fatty liver. They can afford protection against the development of fatty liver. 1. Choline. Feeding of choline has been able to reverse fatty changes in animals. 2. Lecithin and methionine. They help in synthesis of apoprotein and choline formation. The deficiency of methyl groups for carnitine synthesis may also hinder fatty acid oxidation. 3. Vitamin E and selenium give protection due to their anti-oxidant effect. 4. Omega 3 fatty acids present in marine oils have a protective effect against fatty liver. REF : DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, SIXTH EDITION, PG.NO., 143.


Question: Steroid synthesis takes place at

Endoplasmic reticulum (ER): Eukaryotic cells are characterised by several membrane complexes that are interconnected by separate organelles. These organelles are involved in protein synthesis, transpo, modification, storage and secretion. Varying in shape, size and amount, the endoplasmic reticulum (ER) extend from the cell membrane, coats the nucleus, surrounds the mitochondria and appears to connect directly to the Golgi apparatus. These membranes and the aqueous channels they enclose are called cisternae. Types: There are two kinds of the endoplasmic reticulum (ER): (i) Rough surfaced ER, also known as ergastoplasm. They are coated with ribosomes. Near the nucleus, this type of ER merges with the outer membrane of the nuclear envelope. (ii) Smooth surfaced ER: They do not have attached ribosomes. Functions (a) Function of rough ER: Rough ER synthesises membrane lipids, and secretory proteins. These proteins are inseed through the ER membrane into the lumen of the cisternae where they are modified and transpoed through the cell. (b) Function of smooth ER: Smooth endoplasmic reticulum is involved: (i) In lipid synthesis and (ii) Modification and transpo of proteins synthesised in the rough ER Note: A number of impoant enzymes are associated with the endoplasmic reticulum of mammalian liver cells. These include the enzymes responsible for the synthesis of sterol, triacylglycerol (TG), Phospholipids (PL) and the enzymes involved in detoxification of drugs. Cytochrome P450 which paicipates in drug hydroxylation reside in the ER.Ref: Textbook of Medical Biochemistry, Eighth Edition, Dr (Brig) MN Chatterjea, page no: 7-8


Question: The best source of potassium is


Question: Vitamin also acting as hormone

Vitamin D is not strictly a vitamin since it can be synthesized in the skin the dietary source is required only when sunlight exposure is inadequate Its main function is in the regulation of calcium absorption and homeostasis most of the actions of vitD mediated by nuclear receptors. ref harpers biochemistry 30th ed page 551


Question: A large, protruding jaw; large hands and feet; normal height; and an elevated blood glucose level.

In acromegaly, the height is normal, but the jaw, hands, feet, and soft tissues grow. DM frequently occurs because of the stimulation of gluconeogenesis by GH and the inability of glucose to suppress the release of GH by the tumor.

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: The rate limiting enzyme in glycolysis is

(Phosphofroctokinase) (152- Harper 27th) (108- Lippincott's)Phosphofroctokinase - is the pace- setting (rate- limiting) enzyme of glycolysis. It is inhibited by ATP and citrate uses fructose 6- phosphate as substrate, and catalyzes a reaction that is for from equilibrium. The reaction is activated by fructose 2- 6 biphosphate


Question: Aspaate transaminase, an enzyme, is most abundant in

In old literature, it was called as serum glutamate oxaloacetate transaminase (SGOT). AST needs pyridoxal phosphate (vitamin B6) as co-enzyme. ii. Normal serum level of AST ranges from 8 to 20 U/L. It is a marker of liver injury and shows moderate to drastic increase in parenchymal liver diseases like hepatitis and malignancies of the liver. iii. AST was used as a marker of myocardial ischemia in olden days. The level is significantly elevated in myocardial infarction. The time course of AST increase in blood is given in Figure 23.2. iv. But troponins have replaced AST as a diagnostic marker in ischemic hea disease.Ref: DM Vasudevan, Page no: 269


Question: Glucose is conveed to sorbitol by

In lens, the enzyme aldose reductase reduces monosaccharides to corresponding sugar alcohols; glucose to sorbitol and galactose to galactitol. POLYOL PATHWAY OF GLUCOSE - Sorbitol is very poorly absorbed from intestine. It involves the reduction of glucose by aldose reductase to sorbitol, which can then be oxidized to fructose. This would amount to the interconversion of glucose to fructose. Glucose when conveed to sorbitol, cannot diffuse out of the cell easily and gets trapped there. Sorbitol is normally present in lens of eyes. But in diabetes mellitus, when glucose level is high, the sorbitol concentration also increases in the lens. This leads to osmotic damage of the tissue and development of cataract. Galactitol also causes cataract. REF: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, SIXTH EDITION, PG.NO.,119,588.


Question: Glycosaminoglycans located in CNS is

Proteoglycans linked to chondroitin sulfate by the Xyl-Ser O-glycosidic bond are prominent components of cailage. They are located at sites of calcification in endochondral bone and are a major component of cailage. They are found in high amounts in the ECM of the central nervous system and, in addition to their structural function, are thought to act as signaling molecules in the prevention of the repair of nerve endings after injury.Ref: Harper&;s Biochemistry; 30th edition; Chapter 50; The Extracellular Matrix


Question: DNA denaturation is measured by absorbance at

Increase in the optical absorbance of UV light by Purine and Pyrimidine bases called hyperchromicity.( DNA bases absorbs UV light of 260nm).


Question: Column chromatography using phenyl Sepharose beads separates proteins based on the

Hydrophobic interaction chromatography separates proteins based on their tendency to associate with a stationary phase matrix coated with hydrophobic groups(eg.phenyl Sepharose)

Classification and metabolism of amino acids


Question: Carbon atoms added in FA synthesis


Question: DNA synthesis occurs in phase

Cell cycle : In G1 phase , the cell prepares for DNA synthesis. DNA synthesis occurs diring the S (synthesis ) phase of the cell cycle. During the S phase , DNA is completely replicated , but only once. Cell prepares for mitosis in G2 phase, when proteins necessary for daughter cells are synthesized. Then the cell enters into the M phase. Reference : DM.VASUDEVAN.TEXTBOOK SEVENTH EDITION ; PAGE NO :582


Question: Blood group antigens belong to the class

For red blood cells, the membrane oligosaccharides that determine the antigenic natures of the ABO substances appear to be mostly present in glycosphingolipids, whereas in secretions the same oligosaccharides are present in glycoproteins. Some examples of conjugated proteins are lipoproteins, glycoproteins, phosphoproteins, hemoproteins, flavoproteins, metalloproteins, phytochromes, cytochromes, opsins and chromoproteins. so the ABO substances can be chosen as Conjugated proteins from the given options Ref: Harper's Illustrated Biochemistry, 30E (2015) Pg No. 697 chapter 53.


Question: Amino acid with dissociation constant closest to physiological pH is

To understand dissociation constant (pKa) of amino acids one must know the ionizable groups of amino acids.
Each amino acid has two ionizable groups (i) α-carboxyl group (-COOH), and (ii) α-amino group (-NH2).
Besides these two groups, some amino acids have special ionizable groups. e.g. -SH of cysteine, imidazole of histidine.
The dissociation constant (pKa) is the value of pH at which any ionizable group of the amino acid is in 50% ionized form and 50% non-ionized form.
Thus, each amino acid has two pKa values:-

pk1:- pH at which 50% of amino acid molecules have a-carboxyl group in the ionized form (COO-) and 50% molecules have it in unionized form (COOH).
pk2:- pH at which 50% of amino acid molecules have an a-amino group in the ionized form (NH3+) and 50% molecules have it in unionized form (NH2).

The value of pk-1 and pk-2 is different for different amino acids. But it ranges between 3.5-4.0 for pk-1 (i.e. pKa of α -carboxyl group is 3.5-4.0) and 8.0-9.0 for pk-2 (i.e. pKa of a-amino group is 8.0-9.0).

Beside a-carboxyl and a-amino group, some amino acids contain special ionizable group, which will provide one more pKa value (pk3). For example pKa of imidazole group of histidine ranges between 6.5-7.4. That means somewhere between pH 6.5-7.4, 50% of histidine molecules in a solution will have imidazole group in ionized form and 50% molecules will have in unionized form


Question: The enzyme responsible for unwinding of DNA is

Classes of Proteins Involved in Replication Protein Function DNA polymerases Deoxynucleotide polymerization Helicases ATP -driven processive unwinding of DNA Topoisomerases Relieve torsional strain that results from helicase-induced unwinding DNA primase Initiates synthesis of RNA primers Single-strand binding proteins (SSBs) Prevent premature reannealing of dsDNA DNA ligase Seals the single strand nick between the nascent chain and Okazaki fragments on lagging strand Harper30e pg: 378


Question: To be defined as a ganglioside,a lipid substance isolated from nervous tissue must contain

Gangliosides are the complex glycosphingolipids derived from glucosylceramide that contain in addition one or more molecules of sialic acid. Neuraminic acid is the principal sialic acid found in human tissues. Gangliosides are present in nervous tissue in high concentration.They help in cell-cell recognition and communication and as receptors for hormones and bacterial toxins. Reference: Harpers illustrated biochemistry 30 th edition

NANA,hexose,sphingosine,long chain fatty acid,


Question: Glycolytic enzyme(s) inhibited by fluoride


Question: An example of chromoprotein is

Chromoproteins: These are proteins with coloured prosthetic groups. Hemoglobin (Heme, red); Flavoproteins (Riboflavin, yellow), Visual purple (Vitamin A, purple) are some examples of chromoproteins.
Reference: Vasudevan 7th  ed, pg 43


Question: Radiosensitive stage of cell cycle

Radiation and cell cycle M phase followed by g2-m interphase is when the cell is radiosensitive. (g2m interphase > G2 > M) The cell is vulnerable to radiation in the stage of mitosis (m), less so during synthesis (s) and relatively insensitive during resting periods.Four impoant processes that occur after radiation exposure can be summarized as the "four r&;s" of radiobiology*The first is repair. Repair is temperature dependent and is thought to represent the enzymatic mechanisms for healing intracellular injury.The second r is reoxygenation, a process whereby oxygen (and other nutrients) are actually better distributed to ble cells following radiation injury and cell killing*the third r is repopulation, the ability of the cell population to continue to divide and to replace dying and dead cells.*The fouh r is redistribution, which reflects the variability of a cell&;s radiosensitivity over the cell cycle.Ref: Principles of radiation therapy by Deeley, 27; Harrison&;s principles of internal medicine 16th edition, 435


Question: Chylomicrons contain

CHYLOMICRONSSynthesis of chylomicrons Chylomicrons are formed in the intestinal mucosal cells and secreted into the lacteals of lymphatic system (Chapter 11). They are rich in triglyceride (Fig. 12.9). If lipemic serum is kept overnight in the refrigerator, chylomicrons rise as a creamy layer to the top, leaving the subnatant clear. When the chylomicrons are synthesised by the intestinal mucosa, they contain only apo-B-48 and apo-A but apo-C and apo-E are added from HDL in blood during transpo (Fig. 12.10). Metabolism of ChylomicronsMain sites of metabolism of chylomicrons are adipose tissue and skeletal muscle. The half-life of chylomicrons in blood is about 1 hour.The enzyme lipoprotein lipase (LpL) is located at the endothelial layer of capillaries of adipose tissue, muscles, and hea; but not in liver. Apo C-II present in the chylomicrons activates the LpL. The LpL hydrolyses triglycerides present in chylomicrons into fatty acids and glycerol. Muscle or adipose tissue cells take up the liberated fatty acids.Following injection of heparin, the LpL is released from the tissues and lipemia is thus cleared. This is called post-heparin lipolytic activity. Lack of C-II leads to decreased activity of LpL and consequent accumulation of chylomicrons and VLDL in blood. Insulin increases LpL activity.Liver Takes up Chylomicron Remnants As the TAG content is progressively decreased, the chylomicrons shrink in size. These remnants containing apo-B-48 and apo-E are taken up by hepatic cells by receptor-mediated endocytosis. Apo-E binds the hepatic receptorsFunction of ChylomicronsChylomicrons are the transpo form of dietary triglycerides from intestines to the adipose tissue for storage, and to muscle or hea for their energy needsRef: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 153


Question: Has its release inhibited by thyroxine.

Thyroxine (the end product) inhibits the release of TSH by the anterior pituitary. Thyroxine has no effect on the release of LH, PRL, GH, or FSH.


Question: Von Gierke&;s occurs due to deficiency of

Glycogen storage disease type I (GSD I) or von Gierke&;s disease, is the most common of the glycogen storage disease. This genetic disease results from deficiency of the enzyme glucose-6-phosphatase and has an incidence in the American population of approximately 1 in 100,000 bihs.Ref: DM Vasudevan, 7th edition, page no: 128


Question: The pathways that can produce energy even in the absence of O2 is

In Glycolysis--in Absence of O2 (Anaerobic Phase) * In absence of O2, reoxidation of NADH at glyceraldehyde-3-P-dehydrogenase stage cannot take place in the electron-transpo chain. * But the cells have limited coenzyme. Hence to continue the glycolytic cycle NADH must be oxidised to NAD+. This is achieved by reoxidation of NADH by conversion of pyruvate to lactate (without producing ATP) by the enzyme lactate dehydrogenase. SECTION FOUR * It is to be noted that in the reaction catalysed by glyceraldehyde-3-P-dehydrogenase, therefore, no ATP is produced. In anaerobic phase per molecule of glucose oxidation 4 - 2 = 2 ATP will be produced. + 2 ATPRef: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 332


Question: Substrate level phosphorylation is catalysed by

In glycolysis, The enzyme pyruvate kinase transfers a P from phosphoenolpyruvate (PEP) to ADP to form pyruvic acid and ATP Result in step 10. Details: The final step of glycolysis conves phosphoenolpyruvate into pyruvate with the help of the enzyme pyruvate kinase. As the enzyme's name suggests, this reaction involves the transfer of a phosphate group. The phosphate group attached to the 2' carbon of the PEP is transferred to a molecule of ADP, yielding ATP. Again, since there are two molecules of PEP, here we actually generate 2 ATP molecules.Ref: DM Vasudevan, 7th edition, page no: 111


Question: TCA is not controlled by

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. Hence NADPH is note controlled.Ref: DM Vasudevan, 7th edition, page no: 250


Question: Energy source of brain in later pa of starvation

Brain and starvation: During starvation, a significant pa (60-70%) of the energy requirement of the brain is then met by ketone bodies. Under conditions of paial anoxia, the production of ammonia is increased. This is immediately trapped as glutamine. The NH2 group of glutamine and glutamate can be used for synthesis of other amino acids.Ref: DM Vasudevan, 7th edition, page no: 100


Question: Ribosomes have following enzymatic activity

Evidence That rRNA Is a Peptidyl Transferase * Ribosomes can make peptide bonds (albeit inefficiently) even when proteins are removed or inactivated. * Ceain pas of the rRNA sequence are highly conserved in all species. * These conserved regions are on the surface of the RNA molecule. * RNA can be catalytic in many other chemical reactions. * Mutations that result in antibiotic resistance at the level of protein synthesis are more often found in rRNA than in the protein components of the ribosome.Ref: Harpers Illustrated Biochemistry, 30th edition, page no: 423, table 37-3


Question: Lipid with highest mobility is

Classification Based on Electrophoretic Mobility (Frederickson and colleagues, 1967): The most widely used and simplest classification for lipoproteins is based on the separation of major four classes by electrophoresis. The most frequently employed electrophoretic media are "paper" and 'agarose'. Plasma lipoproteins separated by this technique are classified in relation to the comparable migration of serum proteins.On electrophoresis, the different fractions according to mobility appear at:The origin is chylomicrons,Migrating into b-globulin region is called b-lipoproteins (LDL)Migrating into Pre-b-globulin region, called as pre-b-lipoproteins (VLDL)Migrating to "a1-globulin region called a-lipoproteins (HDL)Ref: Textbook of Medical Biochemistry 8th Edition Dr (Brig) MN Chatterjea, Rana Shinde, page no; 444, 445


Question: Multienzyme complex in humans

Fatty acid synthetase

Enzymes used in the fatty acid synthesis are multienzyme complexes:-

Acetyl-CoA carboxylase
Fatty acid synthase


Question: Hexokinase is

A hexokinase is an enzyme that phosphorylates hexoses (six-carbon sugars), forming hexose phosphate. In most organisms, glucose is the most impoant substrate of hexokinases, and glucose-6-phosphate is the most impoant product. Hexokinase can transfer an inorganic phosphate group from ATP to a substrate.


Question: Termination of the synthesis of the RNA molecule is signaled by a sequence in the template strand of the DNA molecule, a signal that is recognized by a termination protein, the

There are two major termination strategies found in bacteria: Rho-dependent and Rho-independent. In Rho-dependent termination, the RNA contains a binding site for a protein called Rho factor. Rho factor binds to this sequence and stas "climbing" up the transcript towards RNA polymerase. When it catches up with the polymerase at the transcription bubble, Rho pulls the RNA transcript and the template DNA strand apa, releasing the RNA molecule and ending transcription. Another sequence found later in the DNA, called the transcription stop point, causes RNA polymerase to pause and thus helps Rho catch up.^4 Rho-independent termination depends on specific sequences in the DNA template strand. As the RNA polymerase approaches the end of the gene being transcribed, it hits a region rich in C and G nucleotides. The RNA transcribed from this region folds back on itself, and the complementary C and G nucleotides bind together. The result is a stable hairpin that causes the polymerase to stall. In a terminator, the hairpin is followed by a stretch of U nucleotides in the RNA, which match up with A nucleotides in the template DNA. The complementary U-A region of the RNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, produces enough instability for the enzyme to fall off and liberate the new RNA transcript. Reference: Harpers illustrated biochemistry 30th edition


Question: Cofactor for glutathione peroxidase

Selenocysteine is abbreted as SeCys. It is seen at the active site of the following enzymes: a) Thioredoxin reductase; b) Glutathione peroxidase, which scavenges peroxides; c) 5&;- De-iodinase that removes iodine from thyroxine to make triiodothyronine and d) Selenoprotein P, a glycoprotein seen in mammalian blood. Replacement of SeCys by Cys will lead to decreased activity of these enzymes. Deficiency of some of these enzymes with the anti-oxidant function may be related to atherosclerosis. Concentration falls in selenium deficiency. Its structure is COOH-CHNH2-CH2-SeH. It is directly incorporated into proteins during the translation process. Biosynthesis of selenocysteine is by replacing the oxygen of serine by selenium; this is done by two steps: Se + ATP - Se-P + AMP + Pi Serine + Se-P - SeCys + Pi Its genetic code is UGA. The tRNA-Sec is the specific tRNA, inseing SeCys. However, normally UGA codon is a stop signal. UGA code for SeCys is identified by a SeCys inseion element in the mRNA, with the help of a specific elongation factor. The tRNA-Sec is first charged with serine, then it is conveed into SeCys. This is then inseed into the correct position when protein is synthesized.Ref: DM Vasudevan, page no: 187


Question: Hemoprosthetic group is found in

Myoglobin is a monomeric protein that acts as a secondary oxygen transpoer and binder in the muscle tissues. Fuhermore, the teiary feature of a myoglobin resembles a water-soluble globule protein characteristics. The diffusion and use of oxygen in the muscles are necessary for the bodily system processes such as respiration. Myoglobin has 8 right-handed a-helices separately forming a polypeptide chain and each contains a single heme prosthetic group with a central bound iron atom.Ref: Text book of biochemistry for medical students. seventh edition, page no: 240 and 294


Question: Mothers with phenylketonuria (PKU) are at increased risk of having children with

Women with PKU who plan to conceive and are not already on a phenylalanine-restricted diet should be counseled to adhere to the diet before conception and throughout pregnancy. Phenylalanine readily crosses the placenta, and high maternal serum levels can result in damage to the fetus or pregnancy loss. Hyperphenylalaninemia causes microcephaly with mental retardation and cardiac defects in the heterozygote fetus who otherwise would not be affected. Impoantly, these defects can be prevented with maternal dietary treatment. Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 347-351


Question: Vitamin H is also known as

Vit H is also known as Biotin. In old literature Biotin was known as anti-egg white injury factor. Biotin was isolated in 1942 by Vincent du Vigneaud, who was awarded Nobel prize in 1955. Reference: DM Vasudevan,Textbook of Biochemistry, pg no. 399


Question: Thiamine deficiency, the thiamine level is best monitored by

(Trans ketolase level in RBC) (377 - Lippencott's 3rd) (167- 7th)* Thiamine deficiency is diagnosed by an increased in erythrocyte transketolase activity observed on addition of thiamine pyrophosphate* The transketolase activity in erythrocytes is decreased Measurement of RBC transketolase activity is a reliable diagnostic test to assess thiamine deficiency. The increase in this enzyme activity (more in severe deficiency) by the addition of TPP is an index of the degree of thiamine deficiency* LA / PA ratio: Abnormal blood lactic acid / Pyruvic acid is said to be more specific indicator of B1 deficiency (160-Rama shinde 6,h)


Question: Normal role of Micro RNA is

MicroRNA (abbreted miRNA) is a small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals, and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression.miRNAs (microRNAs) are sho non-coding RNAs that regulate gene expression post-transcriptionally. They generally bind to the 3&;-UTR (untranslated region) of their target mRNAs and repress protein production by destabilizing the mRNA and translational silencing.


Question: Coenzymes for pyruvate dehydrogenase are A/E


Question: Chalones are of cell division

Chalones are endogenous cell division inhibitorThey inhibit the division by acting on a number of events in cells cycleDue to inhibitory propey on cell division, it has a therapeutic action in cases like cancer.


Question: Lipogenesis occurs in

DE NOVO SYNTHESIS OF FATTY ACIDSThe process of fatty acid synthesis was studied by Feodor Lynen, who got Nobel prize in 1964. The pathway is referred to as Lynn&;s spiral. It is not a reversal of oxidation. Fatty acids are synthesized mainly by a de novo synthetic pathway operating in the cytoplasm. So it is referred to as extramitochondrial or cytoplasmicfatty acid synthase system. The major fatty acid synthesised de novo is palmitic acid, the 16C saturated fatty acid. The process occurs in liver, adipose tissue, kidney, brain, and mammary glandsRef: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 136


Question: Conversion of phenylacetic acid into phenol is an example of

Primary alcohols can be oxidised to make aldehydes, which can then be oxidised to carboxylic acids. Phenols and carboxylic acids can't be oxidised as they don't have a hydrogen atom on the carbon atom to which the OH group is attached.


Question: Immediate precursor of acetoacetate

Immediate precursor of acetoacetate (ketone body) is HMG CoA, not Acetoacetyl CoA.


Question: In alkaptonuria the urine contains

Alkaptonuria is an autosomal recessive Condition. The metabolic defect is deficiency of homogentisate oxidase. this results in excretion of homogentisic acid in urine.Ref: DM Vasudevan - Textbook of Biochemistry for Medical Students, 7th edition, page no: 237


Question: Melatonin is synthesised from

Tryptophan is conveed to Seratonin, which is acetylated. Fuher methylated with the help of S-adenosyl methionine to form Methionine.Ref: DM Vasudevan - Textbook of Biochemistry for Medical Students, 7th edition, page no: 241


Question: The predominant isoenzyme of LDH in cardiac muscle is

Lactate dehydrogenase (LDH) is a tetrameric enzyme consisting of two monomer types: H (for the hea) and M (for muscle) that combine to yield five LDH isozymes: HHHH (I1), HHHM (I2), HHMM (I3), HMMM (I4), and MMMM (I5). The relative propoions of each subunit in the cells of a paicular organ are determined by tissue-specific patterns in the expression of the H and M genes. Isozyme I1 predominates in hea tissue and isozyme I5 in the liver. Thus, when LDH levels rise in blood plasma, the identity of the injured tissue can be inferred from its characteristic pattern of LDH isozymes. In the clinical laboratory, individual isozymes can be separated by electrophoresis and detected using a coupled assay (Figure 7-12). While historicallyof impoance, the assay of LDH has been superseded as a marker for MI by proteins that appear in plasma more rapidly than LDH.Ref: Harper&;s Biochemistry; 30th edition; Chapter 7; Enzymes: Mechanism of Action


Question: Von Gierke’s disease is caused due to deficiency of

Glycogen Storage Diseases (Glycogenosis)


Question: Reducing sugar in the urine is seen in

Galactosemia

Reducing sugar (galactose) in urine is seen in galactosemia.


Question: A codon consists of

A codon is a sequence of 3 nucleotides from 5' → 3' end corresponds to one amino acid.


Question: Mc Ardles disease is due to deficiency of

Glycogen storage diseases TYPE NAME DEFICIENT ENZYME CLINICAL FEATURES Type I von Gierke's disease Glucose-6-phosphatase Fasting hypoglycemia; hepatomegaly,thrombocyte dysfunction. Type II Pompe's disease Lysosomal maltase Accumulation of glycogen in lysosomes of liver, hea and muscle; death before 2 years Type III Limit dextrinosis (Cori's disease) Debranching enzyme Highly branched dextrin accumulates; Fasting hypoglycemia; hepatomegaly Type IV Amylopectinosis (Anderson's disease) Branching enzyme Glycogen with few branches; hepatosplenomegaly; mild- -hypoglycemia; death by age of 5 Type V McArdle's disease Muscle phosphorylase Excercise intolerance; accumulation of glycogen in muscles Type VI Her's disease Liver phosphorylase Mild hypoglycemia; hepatomegaly; better prognosis than other types REF: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY,EIGHTH EDITION,PG.NO.,144.


Question: Secretory proteins are synthesized in

ER is a network of interconnecting membranes enclosing channels or cisternae, that are continuous from outer nuclear envelope to outer plasma membrane. This will be very prominent in cells actively synthesizing proteins,e.g.immunoglobulin secreting plasma cells. The proteins , glycoproteins and lipoproteins are synthesised in the ER. REFERENCE:DM.VASUDEVAN.Textbook. SEVENTH EDITION ; PAGE NO 12

First in cytoplasm and then in Endoplasmic Reticulum

First in Endoplasmic Reticulum and then in cytoplasm


Question: Glycosphingolipid is made up of


Question: The lipid bilayer of cell membrane exist as

The lipid bilayer shows free lateral movement of its components, hence the membrane is said to be fluid in nature. Fluidity enables the membrane to perform endocytosis and exocytosis. However, the components do not freely move from inner to outer layer or outer to inner layer (flip-flop movement is restricted). During apoptosis (programmed cell death), flip-flop movement occurs. Somewhat similar to a gel.Ref: DM Vasudevan, page no: 11


Question: Separation of proteins based on size is done by


Question: The major source of ammonia in kidney

Glutamic acid acts as a link between amino acids and ammonia.Ammonia, which is highly toxic, arises in humans primarily from the a-amino nitrogen of amino acids. Tissues, therefore, conve ammonia to the amide nitrogen of the nontoxic amino acid glutamine. Subsequently, in kidney cells, ammonia generated on purpose from glutamine with the help of Glutaminase.Ref: Harper&;s biochemistry; 30th edition; Chapter 28 Catabolism of Proteins & of Amino Acid Nitrogen


Question: Second messengers, DAG and IP3 are formed from

Phosphatidylinositol Is a Precursor of Second MessengersThe G proteins activate phospholipase C, which hydrolyzes phosphatidylinositol4,5-bisphosphate to produce diacylglycerols and the water-soluble second messenger inositol 1,4,5-triphosphate (IP3).Ref: Harper&;s Biochemistry; 30th edition; Chapter 54; White Blood Cells


Question: Rothera&;s test used for detection of

The presence of ketosis can be established by the detection of ketone bodies in urine by Rothera&;s test.Rothera&;s test: Saturate 5 mL of urine with solid ammonium sulfate. Add a few drops of freshly prepared sodium nitroprusside followed by 2 mL of liquor ammonia along the sides of the test tube. Development of a purple ring indicates the presence of ketone bodies in urine. Strip tests based on the same principle are also available.Ref: D M Vasudevan 7th edition Page no: 166


Question: tRNA combines with

i.e. (mRNA): (308-310-Harper 28th) (554-U-satyanarayan 3rd) (418-Lippincot's 5th)Transfer RNA (tRNA)* tRNA are the smallest (4S) of the three major types of RNA molecules (15%)* The tRNA molecules contain a high percentage of unusual bases (for example-dihydrouracil) and have extensive inter chain base pairing that leads to characteristic secondary and tertiary structures* Each tRNA serves as an "adaptor " molecules that carries its specific amino acid - Covalently attached to its 3 ' end to site ofprotein synthesis. There it recognizes the genetic code sequence of an mRNA, which specifies the addition of its aminoacid to the growing peptide chain. mRNAs and si RNAs cause inhibition of gene expression by decreasing specific protein production, albeit via distinct mechanisms, Both represent exciting new potential targets for therapeutic drug development1. miRNAs - Micro RNAs are typically 21-25 nucleotides long RNA species derived from RNA polymerase II*** transcription units. The small processed mature miRNAs typically hybridize via the formation of imperfect RNA-RNA duplexes within the 3'-untransIated regions of specific target mRNAs leading via poorly understood mechanism to translation arrest2. SiRNAs - silencing RNAs 21 = 25nt in length generated by selective nucleolytic degradation of double stranded RNAs of cellular or viral origin* These short siRNAs usually form perfect RNA-RNA hybrids* SiRNAs are frequently used to decrease or "Knock down99 specific protein levels


Question: The glycolytic enzyme Enolase is inhibited by


Question: Amino acid carrying ammonia from muscle to liver

Under conditions of starvation, the glucose alanine cycle is of special metabolic significance (Fig. 9.30). Alanine is quantitatively the most impoant amino acid taken up by the liver from peripheral tissues, paicularly from skeletal muscle. It forms a major paicipant in inter-organ transpo of nitrogen (Figs 14.4 and 14.5).Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 187


Question: Fluoride inhibits

Ans. d (Enolase) (Ref Harper 28th/150)# Enolase is the enzyme of glycolysis pathway that converts 2-phosphoglycerate into phosphoenol pyruvate and is inhibited by "Fluoride".# The blood is preserved with "NaF".Fluoride inhibits the Enolase, which is an enzyme of glycolysis.EnzymeInhibitorPathway 1.AconitaseFluoroacetate0Krebs cycle2.L-KG dehydrogenaseArseniteKrebs cycle3.EnolaseFluoride0Glycolysis4.Succinate dehydrogenaseMalonate oxaloacetateKrebs cycle5.Glyceradehyde 3-phosphateLactoacetate dehydrogenaseGlycolysis6.MOAIproniazid0-7.Pyruvate dehydrogenaseArsenite-8.Carbonic anhydraseSulfanilamide-# ESR determination:- Westergren's method: 3.8% sodium citrate solution used as anticoagulant.- Wintrobe's method: 2 mg of potassium oxalate and 3 mg of Ammonium oxalate as anticoagulant (double oxalate)# For measurement of BT, CT, PT 3.8% sodium citate solution used as anticoagulant.# For blood transfusion: blood stored in (Anticoagulant used for blood transfusion)- Acid citrate dextrose (ACD) for 21 days- Citrate phosphate dextrose (CPD) for 35 days# Saline adenosine.


Question: Most common genentic enzyme defect in urea cycle is

OTC combines carbamyl phosphate with ornithine to make citrulline which is subsequently processed tourea (see: cycle diagram). Along with CPSI and NAGS deficiency, OTCdeficiency is the most severe of theurea cycle disorders. Patients with complete OTC deficiency rapidly develop hyperammonemia in the newborn period Ref-Harpers illustrated biochemistry 30/e p583


Question: Glutathione is a

Glutathione is -glutamyl cysteinyl glycine, i.e. glutathione is a tripeptide made up of 3 aminoacyl residues - Glutamate, Cysteine, Glycine Gluta - Glutamate Thi- Sulfur containing (Cysteine) One- Glycine (1 C amino acid) Glutathione is the major intracellular reducing substance/anti-oxidant SH group of glutathione is responsible for its antioxidant function.


Question: Oxaloacetate + Acetyl CoA → Citrate + CoASH. This reaction is

There are two irreversible steps : (i) Oxaloacetate to citrate, catalyzed by citrate synthase, and (ii) α - ketoglutarate to succinyl CoA, catalyzed by α - ketoglutarate dehydrogenase.


Question: Major contribution towards gluconeogenesis

Alanine dominates among transpoed amino acid. It is postulated that pyruvate in skeletal muscle undergo transamination to produce alanine. Alanine is transpoed to liver and used for gluconeogenesis.This cycle is referred to as glucose-alanine cycle Ref: satyanarayana 4th edition , pg: 262


Question: The anticodon region is an impoant pa of the


Question: Vitamin A intoxication cause injury to

Higher concentration of retinol increases the synthesis of lysosomal hydrolases. The manifestations of hypervitaminosis A are attributed to the destructive action of hydrolases, particularly on the cell membranes.
Ref : Satyanarayana, 3rd ed, pg no.123


Question: DNA restriction fragments are separated by

Typically, a DNA molecule is digested with restriction enzymes, and the agarose gel electrophoresis is used as a diagnostic tool to visualize the fragments. An electric current is used to move the DNA molecules across an agarose gel, which is a polysaccharide matrix that functions as a so of sieve. Ref-D.M.Vasudevan 7/e p479


Question: In hemoglobin, iron is bound to

The iron atom of hemoglobin has six coordinated bonds : (i) Four bonds are formed between the iron and nitrogen atoms of porphyrin ring system; (ii) Fifth bond is formed between the nitrogen of histidine (proximal histidine: HisF8) of globin; and (iii) Sixth bond is formed with oxygen.


Question: The major source of NADPH for fatty acid synthesis

HEXOSE MONOPHOSPHATE (HMP) SHUNT An Alternate Pathway for Oxidation of Glucose Synonyms: Variously called as: Hexose monophosphate pathway or shunt Pentose phosphate pathway (PP-pathway) Pentose cycle Phosphogluconate pathway Warburg-Dickens-Lipman Pathway. Sources of NADPH Hexose monophosphate shunt or HMP pathway is the main source of NADPH. Oxaloacetate produced by citrate lyase in the cytoplasm can be reduced to malate by NADH + H+ and malate dehydrogenase. There is another cytoplasmic enzyme called malic enzyme (NADP-malate dehydrogenase). Malate is oxidatively decarboxylated to pyruvate and NADPH is produced. An enzyme called isocitrate dehydrogenase is present in the cytoplasm. It generates NADPH mainly in ruminants. It uses NADP as the coenzyme.Ref: Textbook of Medical Biochemistry, Eighth Edition, Dr (Brig) MN Chatterjea, page no: 354,418


Question: Enzyme marker for pancreas

CPK -creatine phosphokinase is an enzyme which is increased in myocardial infarction. Amylase is produced by the pancreas and salivary glands. Increased in acute pancreatitis SGOT- elevated in myocardial infarction ALT elevated in liver diseasesRef: DM Vasudevan, 7th edition, box no; 23.4, page no: 308


Question: Amino acids not coded by triplet codona) Lysineb) Hydroxyprolinec) Selenocysteined) Pyrrolysinee) Ornithine

Selenocysteine is 21st AA coded by UGA which is normally a stop codon.
Pyrrolysine is 22nd AA coded by UGA which is also a stop codon normally.
Lysine is also an essential amino acid so has to be coded by codon (AAA, AAG).
Hydroxyproline and hydroxylysine are not coded by a codon, i.e. they are not incorporated into protein during translation. Rather, they are formed in protein, by post-translational modification (hydroxylation) of proline and lysine, respectively.
"Ornithine is not an amino acid coded for by DNA, and, in that sense, is not involved in protein synthesis.


Question: Same aminoacid is coded by multiple codons due to following


Question: Cereals are deficient in


Question: Uronic acid level in urine is elevated in

MUCOPOLYSACCHARIDOSES The mucopolysaccharidoses 7are hereditary diseases (1:25,000 live bihs) caused by a deficiency of any one of the lysosomal hydrolases normally involved in the degradation of heparan sulfate and/or dermatan sulfate . They are progressive disorders characterized by lysosomal accumulation of GAGs in various tissues, causing a range of symptoms, such as skeletal and extracellular matrix deformities, and intellectual disability. All are autosomal recessive disorders except Hunter syndrome, which is X linked. Children who are homozygous for any one of these diseases are apparently normal at bih and then gradually deteriorate. In severe cases, death occurs in childhood. There currently is no cure. Incomplete lysosomal degradation of GAGs results in the presence of oligosaccharides in the urine. These fragments can be used to diagnose the specific mucopolysaccharidosis by identifying the structure present on the nonreducing end of the oligosaccharide, because that residue would have been the substrate for the missing enzyme. Diagnosis is confirmed by measuring the patient's cellular level of the lysosomal hydrolases. Bone marrow and cord blood transplants, in which transplanted macrophages produce the enzymes that degrade GAGs, have been used to treat Hurler and Hunter syndromes, with limited success. Enzyme replacement therapy is available for both syndromes but does not prevent neurologic damage. Ref : Lippincotts biochemistry 5th edition page no:310


Question: Cyanide affects respiratory chain by

The toxicity of cyanide is due to its inhibitory effect on the terminal cytochrome which brings cellular respiration to a standstill. The inhibitor usually binds to a different domain on the enzyme, other than the substrate binding site. Since these inhibitors have no structural resemblance to the substrate, an increase in the substrate concentration generally does not relieve this inhibition.Ref: DM Vasudevan, Page no: 234


Question: Wernicke's encephalopathy occurs due to deficiency of

(A) Vitamin B1 # Dry Beriberi involves both the peripheral and the central nervous systems.> Peripheral nerve involvement is typically asymmetric motor & sensory neuropathy with pain, paresthesias& loss of reflexes.> The legs are affected more than the arms. Central nervous system involvement results in Wernicke-Korsakoff syndrome.> Wernicke's encephalopathy consists of nystagmus progressing to ophthalmoplegia, truncal ataxia & confusion> Koraskoff's syndrome includes amnesia, confabulation, and impaired learning.


Question: The enzyme primarily responsible for protein degradation in the stomach is

Secretions from the Oxyntic (Gastric) Glands:It is composed of three types of cells: (1) mucous neck cells, which secrete mainly mucus; (2) peptic (or chief) cells, which secrete large quantities of pepsinogen; and (3) parietal (or oxyntic) cells, which secrete hydrochloric acid and intrinsic factor. When pepsinogen is first secreted, it has no digestive activity. However, as soon as it comes in contact with hydrochloric acid, it is activated to form active pepsin.Pepsin functions as an active proteolytic enzyme in a highly acidic medium (optimum pH 1.8 to 3.5), but above a pH of about 5 it has almost no proteolytic activity and becomes completely inactivated in a sho time.Ref: Guyton; 13th edition; Chapter 65 Secretory Functions of the Alimentary Tract


Question: Lipid is required in the average diet because it

is necessary for storage of carbohydrates


Question: Excessive ultraviolet (UV) radiation is harmful to life. The damage caused to the biological systems by ultraviolet radiation is by

Although UV photons of different energies have various effects on DNA, the most impoant damage to DNA is the formation of pyrimidine dimers. In the pyrimidine dimer, two adjacent pyrimidine bases--cytosine (C) and/or thymine (T)--are linked in an abnormal structure which distos the shape of the DNA double helix and blocks its copying by the DNA replication or RNA transcription machinery. A block in either of these impoant processes would be very dangerous for a cell; as little as one dimer per cell in fact, can be lethal. Dimers are formed in DNA most efficiently by UV-C, less efficiently by UV-B, and very little by UV-A action.


Question: A Mucopolysaccharide that do not contain uronic acid (UA)

Ans. d (Keratan Sulphate) (Ref. Harper's Biochemistry-26th ed. 544 and 27th ed. 553)Mucopolysaccharides constitute a major part of connective tissue and consist of units of disaccharides, nitrogen, and sulfate groups. In mucopolysaccharidoses, acid polysaccharides are abnormally deposited in the tissues and excreted in the urine. Acid mucopolysaccharide yield N5 acetyl-hexosamine (a substituted sugar) and uronic acid. Neutral mucopolysaccharides comprise of N5 acetyl-hexosamine and a hexose. Major acid mucopolysaccharides are hyaluronic acid, chondroitin sulphate, chondroitin 6-sulfate, dermatan sulfate, heparan, and heparin. Keratan sulfate (of cornea or bones) is neutral mucopolysaccharide.GAGSugarsSulfateLinkage of proteinLocationHAGIcNAc, GlcUANilNo firm evidenceSynovial fluid, humor, loose connective tissueCSGalcNAc, GlcUAGalNAcXyl-Ser; associated with HA via link proteinsCartilage, bone, corneaKSIIGlcNAc, GalGIcNAcGlcNAc-AsnCorneaKSIGlcNAc, GalSame as KSIGlcNAc-ThrLoose connective tissueHeparinGlcN, ldUAGlcNSerMast cells GlcN ldUA HaparanGlcN, GlclIAGlcNXyl-SerSkin fibroblasts, aortic wallsulphateGalNAC, IdUAGalNAcXyl-SerWide distribution (GLCUA)ldUa Educational points:NameAlternative designatorsEnzyme defectUrinary metabolitesMucopolysaccharidosesHurler, Scheie,MPSIa-L-iduronidaseDermatan sulfate, heparan sulfateHurler-ScheieHunterSanfilippo AMPSIIMPS IMAIduronate sulfataseHeparan sulfateN-sulfatase (sulfamidase)Dermatan sulfate, heparan sulfateHeparan sulfateSanfilippo BMPS IIIBa-N-AcetylglucosaminidaseHeparan sulfateSanfilippo CMPS MICAcetyltransferaseHeparan sulfateSanfilippo DMPS MIDN-Acetylglucosamine 6-sulfataseHeparan sulfateMorquio AMPS IVAGalactosamine 6-sulfataseKeratan sulfate, chondroitin 6 sulfateMorquio BMPS IVBb-GalactosidaseKeratan sulfateMaroteaux - LamyMPS VIN-Acetylgalactosamine 4- sulfatase (arysulfatase B)Dermatan sulfateSlyMPS VIIb-GlucuronidaseDermatan sulfate, heparan sulfate chondroitin 4-sulfate, chondroitin 6- sulfateMucolipidosesSialidosis (MIM)ML ISialidaseGlycoprotein fragmentsI-cell disease (MIM)ML IIUDP-N-acetylglucosamine: glycoprotein N-acetylglucosami-ninylphosphotransferase. (Acid hydrolases thus lack phos-phomannosyl residues.) Pseudo-Hurler polydys- trophyML IIIAs for ML II but deficiency is incompleteGlycoprotein fragments


Question: Eukaryotic DNA polymerase involved in proofreading and DNA repair during replication is

In bacteria, all three DNA polymerases (I, II and III) have the ability to proofread, using 3' - 5' exonuclease activity. ... In eukaryotesonly the polymerases that deal with the elongation (delta and epsilon) have proofreading ability (3' - 5' exonuclease activity) Ref satyanarayana 4e


Question:
Von Geirke’s occurs due to deciency
of

o Glucose – 6- phosphatase is deficient in Von Gierke’s disease


Question: Scurvy is due to deficiency of

Deficiency of ascorbic acid results in scurvy, a disease characterized by sore and spongy gums, loose teeth, fragile blood vessels, swollen joints, and anemia. Many of the deficiency symptoms can be explained by a deficiency in the hydroxylation of collagen, resulting in defective connective tissue.Reference: Lippincott; 5th Edition; Page no: 377


Question: Amino acid connot be used for glycogen synthesis

Ans. is 'c' i.e., Leucine Synthesis of glucose from non-carbohydrate precursors is called gluconeogenesis. When the end product is glycogen instead of glucose, the process is called glyconeogenesis, i.e., synthesis of glycogen from noncarbohydrate precursors. Terms gluconeogenesis and glyconeogenesis are used interchangeably as all reactions are same except for last where glucose-6-phosphate enters the glycogen synthesis pathway, instead by being conveed to glucose. Coming back to question Alanine, threonine and methionine are glucogenic amino-acids, i.e. can be used as substrates for gluconeogenesis or glyconeogenesis. Leucine is purily ketogenic amino acid, can not be used as a substrate for gluconeogenesis or glyconeogenesis.


Question: In DNA, adenine always pairs with

Chargaff observed that in DNA molecules the concentration of deoxyadenosine (A) nucleotides equals that of thymidine (T) nucleotides (A = T), while the concentration of deoxyguanosine (G) nucleotides equals that of deoxycytidine (C) nucleotides (G = C), led Watson, Crick, and Wilkins to propose in the early 1950s a model of a double-stranded DNA molecule. The model they proposed is depicted in Figure 34-2. The two strands of this double-stranded helix are held in register by both hydrogen bonds between the purine and pyrimidine bases of the respective linear molecules and by van der Waals and hydrophobic interactions between the stacked adjacent base pairs. The pairings between the purine and pyrimidine nucleotides on the opposite strands are very specific and are dependent upon hydrogen bonding of A with T and G with CRef: Harpers Illustrated Biochemistry, 30th edition, page no: 360


Question: Immediate source of energy is

In the living cell, the principal high-energy intermediate or carrier compound is adenosine triphosphate (ATP) The impoance of phosphates in intermediary metabolism became evident with the discovery of the role of ATP, adenosine diphosphate (ADP), and inorganic phosphate (Pi) in glycolysisATP plays a central role in the transference of free energy from the exergonic to the endergonic processesThe intermediate position of ATP allows it to play an impoant role in energy transfer. The high free-energy change on hydrolysis of ATP is due to relief of charge repulsion of adjacent negatively charged oxygen atoms and to stabilization of the reaction products, especially phosphate, as resonance hybridsATP is able to act as a donor of high-energy phosphate to form those compounds below it in Table 11-1. Likewise, with the necessary enzymes, ADP can accept high-energy phosphate to form ATP from those compounds above ATP in the table. In effect, an ATP/ADP cycle connects those processes that generate to those processes that utilize, continuously consuming and regenerating ATP. This occurs at a very rapid rate since the total ATP/ADP pool is extremely small and sufficient to maintain an active tissue for only a few seconds.Ref: Harper&;s Biochemistry, 30th edition, page no: 113


Question: Cysteine is synthesized from

Methionine is first conveed to active methionine and then it is conveed to cysteine on combining with serine.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 217, Fig 16.14, 16.15.


Question: To be defined as a ganglioside, a lipid substance isolated from nervous tissue must contain in its structure

Gangliosides They are formed when ceramide oligo-saccharides have at least one molecule of NANA (N-acetyl neuraminic acid) (sialic acid) attached to them. Ceramide--Glucose--galactose--NANA; this is designated as GM3 (ganglioside M3). Gangliosides contribute to the stability of paranodal junctions and ion channel clusters in myelinated nerve fibers. Autoantibodies to GM1 disrupt lipid rafts, paranodal or nodal structures, and ion channel clusters in peripheral motor nerves.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 82

N-Acetylneuraminic acid (NANA), hexoses, sphingosine, long chain fatty acid

NANA, a hexoses, a fatty acid, sphingosine, phosphorylcholine


Question: A membrane phospholipid that does not contain glycerol is

Sphingomyelins are the only sphingolipid that contains phosphate and have no sugar moiety. They are found in large quantities in nervous system. Different sphingomyelins may be formed depending on the fatty acid attached. Common fatty acids found are--lignoceric (24 C), nervonic (24 C, one double bond) and cervonic (22 C, 6 double bonds) acids (Table 7.2). Because of its amphipathic nature sphingomyelin can act as an emulsifying agent and detergent. The relative propoion of lecithin and sphingomyelin is impoant in biological fluids like bile, amniotic fluid, etc. Sphingomyelin combined with fatty acid is called ceramide, which is a component of glycosphingolipids.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 81


Question: Function of Topoisomerases

Classes of Proteins Involved in ReplicationProteinFunctionDNA polymerasesDeoxynucleotide polymerizationHelicasesATP -driven processive unwinding of DNATopoisomerasesRelieve torsional strain that results fromhelicase-induced unwindingDNA primaseInitiates synthesis of RNA primersSingle-strand bindingproteins (SSBs)Prevent premature reannealing of dsDNADNA ligaseSeals the single strand nick between thenascent chain and Okazaki fragments on the lagging strandRef: Harper&;s Biochemistry; 30th edition; Chapter 35; DNA Organization, Replication, & Repair


Question: An aromatic amino acid is

Aromatic amino acids: Phenylalanine, Tyrosine.
Reference: Vasudevan 7th  ed, pg 24


Question: Reverse transcriptase is


Question: 1st product of tryptophan Catabolism

Kynurenine is formed from tryptophan in presence of enzyme tryptophan pyrrolaseRef: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 239, fig 18.8


Question: Polysaccharides are

Polysaccharides are polymers of monosaccharides. They are of two types- homopolysaccharides that contain a single type of monosaccharide (e.g., starch, insulin, cellulose) and heteropolysaccharides with two or more different types of monosaccharides (e.g., heparin, chondroitin sulfate).. Ref: Biochemistry by U. Satyanarayana 3rd edition Pgno : 10


Question: Substrate for ATP synthase is

1. ADP and Pi bind to L binding site 2. LT conversion is by energy-driven conformational change that catalyses the formation of ATP 3. T state reves to O state when ATP is released. 4. L state is regenerated for fuher ADP binding. For the complete rotation of F1 head through the 3 states, 10 protons are translocated. Protons entering the system, cause conformational changes in the F1 paicle. Initially the ADP and Pi are loosely bound to the catalytic site on F1. As the Fo accepts protons, the affinity for ADP is increased (step 1, Fig.19.16). Fuher conformational change induces catalytic activity, and ATP is synthesized (step 2, Fig.19.16). This moves protons to the matrix side. As the ATPs are released, the original conformation of the enzyme is assumed (step 3, Fig.19.16). Then ADP is again bound and the cycle repeats (step 4, Fig.19.16). The energy surplus produced by the proton gradient is stored as chemical energy in ATP. The energy-requiring step is not at the synthesis of ATP, but energy is required for the conformational changes. Regulation of ATP Synthesis The availability of ADP regulates the process. When ATP level is low and ADP level is high, oxidative phosphorylation proceeds at a rapid rate. This is called respiratory control or acceptor control. The major source of NADH and FADH2 is the citric acid cycle, the rate of which is regulated by the energy charge of the cell.Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 233


Question: Menadione is analog of

Three compounds have the biological activity of vitamin K. Phylloquinone, the normal dietary source, found in green vegetables Menaquinones, synthesized by intestinal bacteria, with differing lengths of the side chain and Menadione and menadiol diacetate, synthetic compounds that can be metabolized to phylloquinone. Menaquinones are absorbed to some extent, but it is not clear to what extent they are biologically active as it is possible to induce signs of vitamin K deficiency simply by feeding a phylloquinone deficient diet, without inhibiting intestinal bacterial Reference: Harper; 30th edition; Page no: 554


Question: Carboxylases requires

Pyruvate in the cytoplasm enters the mitochondria. Then, carboxylation of pyruvate to oxaloacetate is catalyzed by a mitochondrial enzyme, pyruvate carboxylase. It needs the co-enzymes biotin and ATP.Ref: DM Vasudevan, page no: 103


Question: Northern blot test is used for

Ans. is 'b' i.e. RNA analysis: Northern blot is used for - RNA analysis*Southern blot is used for - DNA analysis*Western blot is used for - Protein analysis*Mnemonic:South is Down on the globe. [i.e. South-DNA'


Question: Synthesis of rRNA place in

Molecules of rRNA are synthesized in a specialized region of the cell nucleus called the nucleolus, which appears as a dense area within the nucleus and contains the genes that encode rRNA. Ref-D.M.Vasudevan 7/e p572


Question: Enzymes not used in glycogen metabolism

The liver phosphorylase-b is the inactive form. It becomes active on phosphorylation. The active form is phosphorylase-a.Glycogen synthase exists in two distinct forms that can be interconveed by the action of specific enzymes; active dephosphorylated glycogen synthase(glucose-6-p-independent) and less active, phosphorylated glycogen synthase D(glucose-6-p-dependent.Ref: DM Vasudevan, page no: 127


Question: Nucleolus contains

Ans. b (RNA). (Ref: Harper, Biochemistry, 25th ed., 8)CELL# A cell is composed mainly of cytoplasm, cell organelle and a nucleus.# Nucleus is made up of nucleoli.# Nucleus contain number of chromosomes packed together.# Genes are made up of DNA.# The entire genetic information contained in the genes is packaged in the chromosomes.# All the somatic cells of an individual organism contain the same number of chromosomes.# The genes are arranged linearly on the chromosomes and their positions on the normal chromosome in relation to other genes on the same chromosome are fixed. This position is called the locus.# Genes occupying the same locus on a pair of chromosomes are called alleles.# The highly methylated ribosomal RNA are packaged in the nucleolus C specific ribosomal proteins# The rRNA genes are located in the nucleoli of mammal on cells.


Question: Major site of protein glycosylation is

Because many glycosylation reactions occur within the lumen of the Golgi apparatus, carrier systems (permeases and transpoers) are required to transpo nucleotide sugars across the Golgi membrane.Ref: Harpers Illustrated Biochemistry, 30th edition, page no: 572


Question: At physiologic pH, DNA is

Nucleic acid carries negative charge at physiological pH Negative charge at physiologic pH is due to presence of phosphodiester linkages This propey is useful for the separation of DNA or RNA by electrophoresis. DNA will move towards the anode. Shoer DNA molecules will move faster than longer molecules in agarose gel electrophoresis.


Question: Source of energy for a running race athlete for the initial 3 minutes of running

Systems for energy during strenuous exercise or running 1. First System-Phosphagen system (8-10 seconds) - Immediate source of energy for Muscles is Creatine Phosphate. - But this is of limited supply in muscles, so depleted quickly 2. Second system -Anaerobic Glycolysis or Lactate system. (for 1-3 minutes ) - This system derives ATPs using Glucose derived from Muscle Glycogen 3.Third system -Aerobic System (or Mitochondrial Respiration) - can use carbohydrates, Fats, or Proteins to produce energy. - Slowest in providing energy, but more efficient than the other two systems - This system uses mainly TCA & ETC. Reasons for use of Phosphocreatine:- - Does not uses O2 - Does not produce lactate - Quickest source of energy - Most direct form of energy production


Question: Accumulation of glycogen in lysosomes is characteristic in the deficiency of

Type Name Enzyme Deficiency Clinical Features II Pompe disease Lysosomal a1 - 4 and a1 - 6 glucosidase (acid maltase) Accumulation of glycogen in lysosomes: Juvenile onset variant, Muscle hypotonia, Death from hea failure by age 2 Adult-onset variant, muscle dystrophy Reference: Harper; 30th edition; Table: 18-2; Page no: 179


Question: Wernicke's encephalopathy is caused by deficiency of

This disorder is also known as cerebral beriberi mostly seen in chronic alcoholics. demands for Vit(B1) thiamine increase in alcoholism Insufficient intake or impaired intestinal absorption will lead to this syndrome clinical features are ophthalmoplegia nystagmus cerebellar ataxia psychosis ref biochemistry satyanarayana 4th ed page 137 , DM vasudevan 8th ed page 467


Question: Decarboxylation reactions require

Pyruvate dehydrogenase: The co-enzyme form is thiamine pyrophosphate (TPP). It is used in oxidative decarboxylation of alpha-keto acids, e.g. pyruvate dehydrogenase catalyzes the breakdown of pyruvate, to acetyl CoA and carbon dioxide (see Fig. 9.22).Alpha-ketoglutarate dehydrogenase: an analogous biochemical reaction that requires TPP is the oxidative decarboxylation of alpha-ketoglutarate to succinyl CoARef: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 478


Question: After digestion by restriction endonucleases DNA strands can be joined again by

DNA ligase Repeat from May 10 Proteins Involved in Replication Protein Function DNA polymerases Deoxynucleotide polymerization Helicases Unwinding and separation of DNA strands Topoisomerases Relieve torsional strain that results from helicase-induced unwinding (removes supercoils) DNA primase Initiates synthesis of RNA primers Single-strand binding proteins Prevent premature reannealing of dsDNA DNA ligase Seals the single strand nick between the nascent chain and Okazaki fragments on lagging strand DNA gyrase- Its a special type of topoisomerase, has the unusual propey of being able to introduce negative supercoils into resting DNA . This facilitates the future replication of DNA because the negative supercoils neutralise the positive supercoils introduced during opening of the double helix. For understanding of the DNA replication process, flip through the pages of Lippincott Chapter on DNA replication, (p393 in 3rd edition)


Question: Selenocysteine is a pa of

Selenocysteine is abbreted as SeCys. It is seen at the active site of the following enzymes: a) Thioredoxin reductase; b) Glutathione peroxidase, which scavenges peroxides; c) 5&;- De-iodinase that removes iodine from thyroxine to make triiodothyronine and d) Selenoprotein P, a glycoprotein seen in mammalian blood. Replacement of SeCys by Cys will lead to decreased activity of these enzymes. Deficiency of some of these enzymes with the anti-oxidant function may be related with atherosclerosis. Concentration falls in selenium deficiency. Its structure is COOH-CHNH2-CH2-SeH. It is directly incorporated into proteins during the translation process. Biosynthesis of selenocysteine is by replacing the oxygen of serine by selenium; this is done by two steps: Se + ATP - Se-P + AMP + Pi Serine + Se-P - SeCys + PiRef: DM Vasudevan, Page no: 187


Question: The normal Nitrogen content in 200gm protein is

Obligatory nitogen loss is 3.5g of N/day for a 65 kg person (urinary,fecal and cutaneous loss).This cold be equivalent to 22 g of protein. then 200 gm of = ? nitrogen content. =200*3.5/22=31.8=32 gm REFERENCE :DM VASUDEVAN TEXTBOOK EIGHTH EDITION ; Page no:515.


Question: Serum gamma glutamyl transpeptidase increase in (GGT)

(Alcoholism) (107- U. Satyanarayan 3rd)Important enzymes in the diagnosis of diseaseSGPT/ALTLiver disease (Hepatitis)SGOT/ASTMI & Liver diseaseLDHMI, Infective hepatitisCPKMyocardial infarctionAldolasesMuscular dystrophy5- NucleotidaseHepatitisY- Glutamyl- transpeptidases (GGT) -Alcoholism


Question: At isoelectric pH proteina) Have Net charge '0'b) Are positively chargedc) Are negatively chargedd) Don't migrate

its isoelectric pH, amino acid bears no net charge and does not move (migrate) in an electric field.


Question: Not seen in the thiamine deficiency

cerebral beriberi is mostly seen in chronic alcoholics. The body demands of thiamine increase in alcoholism. Insufficient intake or impaired intestinal absorption of thiamine will lead to this syndrome. characterized by loss of memory(amnesia), apathy and a rhythmical to and fro motion of the eye balls (nystagmus), Confabulatory psychosis ref satyanarayana 4th ed page 137


Question: The regulating enzyme in heme synthesis is

(ALA synthase) (276-Lippencott's 3rd) (210- U.S.3rd)Biosynthesis of heme - The major sites of heme biosynthesis are the liver, which synthesizes a number of heme proteins (particularly, cytochrome P450) and the erythrocyte-producing cells of the bone marrow, which are active in hemoglobin synthesis.* ALA-synthase is the rate controlling step in hepatic porphyrin biosynthesis (276-LP)* The first committed step in heme biosynthesis catalyzed by 5-aminolevulinate (ALA) synthase is regulatory. Heme or its oxidized product hemin (Fe+++) controls this enzyme activity by three mechanisms.1. Feedback inhibition2. Repression of ALA synthatase3. Inhibition of transport of ALA synthase from cytosol to mitochondria (the site of action) (21.5-U Satyanarayan 2nd)* ALA synthase is main rate-limiting enzyme in the synthetic pathway (469-Chatterjee & Shinde 6th)* ALA dehydratase is second rate-limiting enzymeRate limiting Enzymes1. Fatty acid synthesisAcetyl Co A carboxylase2. Cholesterol synthesisHMG-Co A reductase3. Bile acid synthesis7 a-hydroxylase4. Prostaglandin synthesisPhospholipase A25. Uric acid synthesisXanthine oxidase6. Catecholamine (epinephrine)Tyrosine hydroxylase (tyrosinase)


Question: Source of maltose is

SugarSourceSucroseCane and beet sugar, sorghum and some fruits and vegetablesLactoseMilkMaltoseEnzymic hydrolysis of starch (amylase);germinating cereals and maltIsomaltoseEnzymic hydrolysis of starch (the branch points in amylopectin)LactuloseHeated milk (small amounts), mainlysyntheticTrehaloseYeasts and fungi; the main sugar of insect hemolymphRef: Harper&;s Biochemistry; 30th edition; Chapter 15 Carbohydrates of Physiological Significance


Question: Arsenite inhibits

Alpha ketoglutarate dehydrogenase (alpha ketoglutarate to succinyl CoA) is inhibited by Arsenite. This is a non-competitive inhibition. Ref: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, SIXTH EDITION,PG.NO.,222.


Question: Apolipoprotein B48


Question: Glycogen storage disorder due to muscle phosphorylase deficiency

McArdle&;s disease: type V glycogen storage disease.Due to deficiency of muscle phosphorylase. Incidence 1 out of 1million.Ref: DM Vasudevan, 7th edition, page no: 144


Question: Oxidative phase of HMP shunt pathway is least active in

Oxidative phase of HMP shunt pathway is least active in skeletal muscle High activity of HMP shunt Low activity of HMP shunt Liver Non-lactating mammary gland Adipose tissue Skeletal muscle Adrenal coex, Thyroid Erythrocytes Testis Lactating mammary gland NOTE: Oxidative phase of HMP shunt cannot occur in kidneys.


Question: Strongest oxygen radical amongst the following is

Reactive Oxygen Species (ROS) radicals like the hydroxyl radical . It is the most reactive of them all; note how it differs from the hydroxyl ion . the superoxide anion which is both ion and radical


Question: Carbon dioxide fixing reaction requires

Biotin-Independent Carboxylation ReactionsCarbamoyl phosphate synthetase, which isthe stepping stone for urea and pyrimidinesynthesis (Step 1, Fig. 14.13).Addition of CO2 to form C6 in purine ring.Malic enzyme, conveing pyruvate to malateGluconeogenesis1. Pyruvate Carboxylase ReactionPyruvate in the cytoplasm enters the mitochondria.Then, carboxylation of pyruvate to oxaloacetate is catalysed by a mitochondrial enzyme, pyruvate carboxylase (Fig. 9.24). It needs the co-enzymes biotin and ATP.Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 415


Question: Operon model was elucidated by

FRANCOIS JACOB and JACQUES MONAD put forward the operon concept in 1965Theory was based on the observation on lactose metabolism in Escherichia coliRef: DM Vasudevan, 7th edition, page no: 617


Question: Gangliosides consist of

Gangliosides are synthesized from ceramide by the addition of activated sugars (eg, UDPGlc and UDPGal) and a sialic acid, usually N-acetylneuraminic acid. Gangliosidoses is accumulation of gangliosides. Ex: Tay-Sachs disease Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 37


Question: Vitamin A is stored in

The liver contains ~90% of the vitamin A reserves and secretes vitamin A in the form of retinol, which is bound to retinol binding protein.Ref: Harrison&;s Principles of Internal Medicine; 19th edition; Chapter 96e; Vitamin and Trace Mineral Deficiency and Excess


Question: Aldolase is a/an

Class 4: Lyases These enzymes can remove groups from substrates or break bonds by mechanisms other than hydrolysis. For example, Fructose-1,6-bisphosphate -------- Glyceraldehyde-3-phosphate +dihydroxy acetone phosphate The enzyme is AldolaseRef: DM Vasudevan, Page no: 41


Question: Ochronosis is caused by

In Alkaptonuria there is defect in catabolism of Tyrosine and Phenylalanine Enzyme deficient-Homogentisate Dioxygenase Homogentisic acid is an intermediate in the catabolism of Tyrosine Deposition of black pigments (polymerization of Homogentisic acid occurring in body over years) in joints, cailage and collagenous tissue is known as Ochronosis. DEPOSITION OF BLACK PIGMENTS

Phenylalanine and Tyrosine metabolism Detail


Question: In the physiologic system, nitric oxide is known to act through


Question: The number of ATPs generated in Krebs cycle are

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. These steps are marked in Figure 18.5 and in Table 18.1. The summary is shown in Box 18.2. Note: Recent work shows that in the electron transpo chain, NADH produces only 2.5 ATPs and FADH only 1.5 ATPs. The old values (used in the Table 18.1. ATP generation steps Step Reactions no. CoATPs ATPs enzyme (old(new calculation) 3Isocitrate - -- Alpha-ketoglutarate dehydrogenase reaction is the only one irreversible step in the cycle. The free energy changes of the reactions of the cycle are such that the cycle will operate spontaneously in the clockwise direction. Only about 33% of energy liberated is trapped as ATP. The rest is used to keep the body temperature at a higher level than the environment.Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 220


Question: Most Basic amino acid is

(C) Arginine # Aminoacid can be acidic, basic or neutral depending up on their side chain.> The lower the Pka of the R gp, the more acidic will be the amino acids, so aminoacid with the highest Pka of the RGP will be most basic.Basic Amino AcidPka of 'R' group* Arginine12.5* Lysine10.8* Histidine6.0


Question: Best indicator of iron deficiency

In iron deficiency anemia, ferritin content is reduced. When iron is given in anemia, the apoferritin production is induced within a few hours. vii. Estimation of ferritin in chronic kidney disease (CKD) is of prognostic significance since ferritin level less than 100 microgram/dl indicates iron deficiency. Transferrin saturation less than 20% and ferritin between 100 and 200 microgram/dl is suggestive of functional deficiency. In order to treat the anemia in CKD, the iron stores should be adequate and this is denoted by serial ferritin estimations in a patient on treatment to check the efficacy of treatment with recombinant erythropoietinRef: DM Vasudevan, page no: 425


Question: The most important function of 23 DPG is

Ref: Harper's Illustrated Biochemistry, 28th edition Explanation:Hemoglobin comes to 'T' form or taut form by 23 BPG (DPG) which is formed during glycolysis. This reduces the affinity of Hb for oxygen and helps in the unloading of oxygen.


Question: HHH syndrome results from the defect in the enzyme is

Ornithine PermeaseThe hyperornithinemia, hyperammonemia, and homocitrullinuria syndrome (HHH syndrome) result from mutation of the ORNT1 gene that encodes the mitochondrial membrane ornithine permease. The failure to impo cytosolic ornithine into the mitochondrial matrix renders the urea cycle inoperable, with consequent hyperammonemia, and hyperornithinemia due to the accompanying accumulation of cytosolic ornithine. In the absence of its normal acceptor (ornithine), mitochondrial carbamoyl phosphate carbamoylates lysine to homocitrulline, resulting in homocitrullinuria.Ref: Harper&;s Biochemistry; 30th edition; Chapter 28; Catabolism of Proteins & of Amino Acid Nitrogen


Question: RDA of thiamine per 1000 kcal energy per day is

RDA of thiamine per 1000kCal energy per day is 0.5mg.Recommended Daily Allowance of Thiamine It depends on calorie intake (0.5 mg/1000 calories). Requirement is 1-1.5 mg/day. Thiamine is useful in the treatment of beriberi, alcoholic polyneuritis, neuritis of pregnancy and neuritis of old age.Reference: Textbook of Biochemistry by D M Vasudevan, sixth edition, pg no. 392


Question: The metabolite that is regarded as the dead end in glycolysis

Lactate is always the end product of glycolysis, lactate has been considered a dead -end waste product. Congruently, the end product of glycolysis has been viewed dichotomously: pyruvate in the presence of adequate oxygenation, La(-) in the absence of adequate oxygenation. In contrast, given the near-equilibrium nature of the lactate dehydrogenase (LDH) reaction and that LDH has a much higher activity than the putative regulatory enzymes of the glycolytic and oxidative pathways, we contend that La(-) is always the end product of glycolysis. Cellular La(-) accumulation, as opposed to flux, is dependent on (1) the rate of glycolysis, (2) oxidative enzyme activity, (3) cellular O2 level, and (4) the net rate of La(-) transpo into (influx) or out of (efflux) the cell. For intracellular metabolism, we reintroduce the Cytosol-to-Mitochondria Lactate Shuttle. Our proposition, analogous to the phosphocreatine shuttle, purpos that pyruvate, NAD(+), NADH, and La(-) are held uniformly near equilibrium throughout the cell cytosol due to the high activity of LDH. La(-) is always the end product of glycolysis and represents the primary diffusing species capable of spatially linking glycolysis to oxidative phosphorylation.


Question: Purine nucleotide synthesis is done from

With the exception of parasitic protozoa, all forms of life synthesize purine and pyrimidine nucleotides. Synthesis from amphibolic intermediates proceeds at controlled rates appropriate for all cellular functions. To achieve homeostasis, intracellular mechanisms sense and regulate the pool sizes of NTPs, which rise during growth or tissue regeneration when cells are rapidly dividing. Glycine is involved in second step of the reaction.Ref: Harpers Illustrated Biochemistry, 30th edition, page no: 348


Question: "Classical phenyl ketonuria" is caused by deficiency of

(Phenylalanine hydroxylase) (470 - RS 7th) (366 - U.S)PHENYLKETONURIA - 5 types of hyperphenylalaminemiasHYPER PHENYLALANINEMIASTypeConditionProbable enzyme defectTreatmentIClassical phenyl ketonuriaPhenylalanine hydroxylaseLow phenylalanine dietIIPeristent hyperphenyl alaninaemiaDecreased phenylalanine hydroxylase enzymeNone but temporary dietery therapyIIITransient mild hyperphenyl alaninaemiaMaturational delay of phenyl alanine hydroxylase enzymesSame as Type IIIVDihydropteridine reductase deficiencyDeficient or absent dihydropteridine reductaseDOPA, 5- 0 H tryptophan, carbidopaVAbnormal dihydrobiopterin functionDihydrobiopterin synthesis defectSame as type IV* Alkaptonuria - homogentisate oxidase deficiency enzyme* Type I Tyrosinaemia - Fumaryl acetoacetate hydrolase enzyme deficiency* Type II Tyrosinaemia - Hepatic transaminase enzyme deficiency* Hereditary tyrosinaemia - pOH - phenyl pyruvate oxidase enzyme deficiency


Question: Low insulin/glucagon levels to increase in the activity of

Insulin has several effects in liver which stimulate glycogen synthesis. First, it activates the enzyme hexokinase, which phosphorylates glucose, trapping it within the cell. Coincidently, insulin acts to inhibit the activity of glucose-6-phosphatase.When the insulin level is decreased, activity of enzyme glucose-6-phosphatase is increased, thereby increasing glycogenolysis and gluconeogenesis


Question: A patient was diagnosed with isolated increase in LDL. His father and brother had the same disease with increased cholesterol. The likely diagnosis is

Type II A (Primary familial hypercholesterolemia) There is elevation of LDL. Patients seldom survive the second decade of life due to ischemic hea disease .The cause is LDL receptor defect. Receptor deficiency in liver and peripheral tissues will result in the elevation of LDL levels in plasma, leading to hypercholesterolemia. The LDL receptor defect may be due to the following reasons: 1. LDL receptor deficiency. 2. Defective binding of B-100 to the receptor. A substitution of glutamine for arginine at 3500thamino acid results in poor binding to LDL receptors. This defect is known as B-3500 or familial defective apo-B. 3. Receptor-LDL complex is not internalised. Secondary type II hyperlipoproteinemia is seen in hypothyroidism, diabetes mellitus, nephrotic syndrome and cholestasisRef: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 300

Familial lipoprotein lipase deficiency (type I


Question: In conversion of DNA to RNA, enzyme required

RNA polymerase also is known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA.In cells, RNAP is necessary for constructing RNA chains using DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses. In chemical terms, RNAP is a nucleotidyl transferase that polymerizes ribonucleotides at the 3&; end of an RNA transcript.


Question: Gluconeogenesis in Fasting state is indicated by

Ans is 'b' i.e. Pyruvate Carboxylase activation by Acetyl CoA "Allosteric activation of hepatic pyruvate carboxylase by acetyl CoA occurs during fasting. As a result of excessive lipolysis in adipose tissue, the liver is flooded with fatty acids. The rate of formation of acetyl CoA by f-oxidation of these fatty acids exceeds the capacity of the liver to oxidize it to CO2 and H2O. As a result, acetyl CoA accumulates and leads to activation of pyruvate carboxylase. Acetyl CoA also inhibits pyruvate dehydrogenase. Thus, this single compound can divert pyruvate toward gluconeogenesis and away from the TCA cycle. Lippincott BiochemistryGluconeogenesis is not simple reversal of glycolysis. There are 10 reactions in glycolysis. Seven of these glycolytic reactions are reversible and are used in the synthesis of glucose from lactate or pyruvate. However, three of the reactions are irreversible. These 3 reactions are circumvented by four alternate reactions.The 3 irreversible reactions of Glycolysis are:Phosphorylation of Glucose to Glucose -6-phosphate by HexokinasePhosphorylation of Fructose-6-phosphate to Fructose 1, 6 -bisphosphate by Phosphofructokinase-1.Conversion of Phosphoenolpyruvate to Pyruvate by Pyruvate kinaseThe reactions unique to gluconeogenesis which circumvent these 3 irreversible reactions are:Pyruvate to Phosphoenolpyruvate by 2 reactions:Pyruvate is carboxylated to Oxaloacetate by Pyruvate carboxylase.Oxaloacetate is converted to Phosphoenolpyruvate by enzyme Phosphoenolpyruvate carboxykinase (PEP carboxykinase).Conversion of Fructose 1, 6-Bisphosphate to Fructose 6-phosphate catalyzed by Fructose 1, 6-bisphosphataseConversion of Glucose 6-phosphate to glucose catalyzed by glucose 6-phosphatase.Since Glycolysis and Gluconeogenesis share the same pathway but in opposite directions, they are regulated reciprocally.Allosteric regulation:Allosteric regulation by acetyl CoAPyruvate carboxylase is allosterically activated by acetyl CoA. .During fasting large amounts of acetyl CoA derived from oxidation of fatty acids, inhibits pyruvate dehydrogenase and activates Pyruvate carboxylase. Thus, acetyl CoA diverts pyruvate toward gluconeogenesis and away from the TCA cycle.Allosteric regulation by AMPFructose 1, 6-bisphosphatase is inhibited by AMP--a compound that activates phosphofructokinase. Elevated AMP thus stimulates glycolytic pathway that oxidize nutrients to provide energy for the cell. (AMP signals "energy-poor" state in the cell.) Conversely, low concentrations of AMP and high levels of ATP stimulate gluconeogenesis.Allosteric regulation by Fructose 2, 6-bisphosphate:Fructose 2, 6-bisphosphate is allosteric inhibitor of fructose 1, 6-bisphosphatase and activator of phosphofructokinase-1.The concentration of fructose 2, 6-bisphosphate is influenced by the levels of circulating glucagon.When there is abundant supply of glucose, the concentration of fructose 2, 6-bisphosphate increases, stimulating glycolysis by activating phosphofructokinase-1 and inhibiting fructose 1, 6-bisphosphatase.The gluconeogenesis pathway. The numbered reactions are unique to gluconeogenesis.In the fasting state Glucagon levels increase. Glucagon lowers the level of fructose 2, 6-bisphosphate, resulting in activation of fructose 1, 6-bisphosphatase and inhibition of phosphofructokinase, thus favoring gluconeogenesis over glycolysis.

Citrate activation by acetyl co-a carboxylase

Fructose 1,6 bisphosphate activates Pyruvate Kinase

Fructose 2,6 bisphosphate activates PFK-1


Question: Pentose phosphate pathway (HMP shunt pathway) produces

HMP shunt pathway gives NADPH and ribose-5-phosphate.


Question: The function of g DNA Polymerase

Ref: Harper&;s Biochemistry; 30th edition; Chapter 35; DNA Organization, Replication, & Repair


Question: Plasma ceruloplasmin is a

Caeruloplasmin It is a copper-containing a2-globulin, a glycoprotein with enzyme activities. Molecular weight is [?] 151,000. It has eight sites for binding copper-contains about eight atoms of copper per molecule- 1/2 as cuprous (Cu+) and 1/2 as cupric (Cu++). It carries 0.35 percent Cu by weight. Normal plasma contains approx. 30 mg/100 ml and about 75 to 100 mg of Cu may be present in 100 ml of plasma. It has enzyme activities, e.g. copper oxidase, histaminase and ferrous oxidase.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 101


Question: Tryptophan load test helps in the evaluation of deficiency of the Vitamin

The synthesis of niacin coenzymes (NAD+ and NADP+) from tryptophan is dependent on PLP The enzyme kynureninase requires PLP. In B6 deficiency, 3-hydroxy anthranilic acid is diveed to xanthurenic acid Increased excretion of xanthurenic acid in urine is an indication of B6 deficiency. ref satyanarayana 4th ed page 145


Question: Addition of PUFA in plasma membrane causes

Ans. is 'b' i.e. increased fluidity of membranes : As explained previously in NOV 2000 paperThe fluidity of the plasma membrane is highly dependent upon the lipid composition of the membrane . * Saturated fatty acids : Increase the transition temperature and hence decrease the fluidity.Unsaturated fatty acids (PUFA) : Decrease the transition temperature and hence increase the fluidity of membrane.


Question: Dietary triglycerides are transpoed by


Question: Prenatal diagnosis of haemophilia is best done by

Noninvasive prenatal diagnosis of hemophilia by microfluidics digital PCR analysis of maternal plasma DNA.Haemophilia is a bleeding disorder with X-linked inheritance. Current prenatal diagnostic methods for haemophilia are invasive and pose a risk to the fetus. Cell-free fetal DNA analysis in maternal plasma provides a noninvasive mean of assessing fetal sex in such pregnancies. However, the disease status of male fetuses remains unknown if mutation-specific confirmatory analysis is not performed. Here we have developed a noninvasive test to diagnose whether the fetus has inherited a causative mutation for haemophilia from its mother. The strategy is based on a relative mutation dosage approach, which we have previously established for determining the mutational status of fetuses for autosomal disease mutations. In this study, the relative mutation dosage method is used to deduce whether a fetus has inherited a haemophilia mutation on chromosome X by detecting whether the concentration of the mutant or wild-type allele is overrepresented in the plasma of heterozygous women carrying male fetuses. We correctly detected fetal genotypes for haemophilia mutations in all of the 12 studied maternal plasma samples obtained from at-risk pregnancies from as early as the 11th week of gestation. This development would make the decision to undeake prenatal testing less traumatic and safer for at-risk families.


Question: Not an aldose sugar

Aldose sugars glyceraldehyde, erythrose, arabinose, xylose, ribose, glucose, galactose, mannoseRef: DM Vasudevan, 7th edition, page no: 76


Question: Mitochondrial DNA is

Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that conve chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Ref-Harpers illustrated biochemistry 30/e p585


Question: Energy currency among carbohydrates is


Question: ATP generated per TCA 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 producedRef: DM Vasudevan, 7th edition, page no: 250


Question: Serotonin is synthesized from

Serotonin is synthesized from tryptophanRef: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 241, fig 18.10


Question: Essential fructosuria is due to deficiency of

Fructosuria is a benign metabolic defect due to deficiency of fructokinase. There is no abnormality in other than excretion of fructose in urine.Ref: DM Vasudevan, 7th edition, page no: 138


Question: Oxaloacetate is formed from

Aminotransferase (transaminase) reactions form pyruvate from alanine, oxaloacetate from aspaate, and a-ketoglutarate from glutamate. Because these reactions are reversible, the cycle also serves as a source of carbon skeletons for the synthesis of these amino acids. Other amino acids contribute to gluconeogenesis because their carbon skeletons give rise to citric acid cycle intermediates. Alanine, cysteine, glycine, hydroxyproline, serine, threonine, and tryptophan yield pyruvate; arginine, histidine, glutamine, and proline yield a-ketoglutarate; isoleucine, methionine, and valine yield succinyl-CoA; tyrosine and phenylalanine yield fumarate. Reference: Harper; 30th edition; Page no: 165


Question: In Glycinuria, glycine is excreted as

(D) Oxalate # Diseases associated with glycine metabolism: are 1. Glycinuria and 2. Primary hyperoxaluria> In Glycinuria there is excessive urinary excretion of glycine with a tendency to form oxalate renal stones. This disease is inborn and very rare.> Primary hyperoxaluria is a metabolic disease characterized biochemically by a continuous and high excretion of oxalate in urine, the excess oxalate probably coming from glycine.> There is recurrent infection of the urinary tract.> In vitamin B6 deficiency also, increased quantities of oxalate are excreted


Question: Glucose transporter present in RBCs

RBC's contain GLUT - 1 transporter.
	GLUT -1 is insulin independent.
	It is also present in Brain and Comea.
GLUT - 2 present in β Cells of pancreas, kidneys, liver, small intestine.
GLUT - 3 is present in Newrons, Placenta.
GLUT - 4 is present in muscles, adipose tissue.
GLUT - 5 also transports fructose and is present in Hepatocyter, seminal vesicles GIT.


Question: The highest quantity of lipid and lowest concentration of protein are found in


Question: Complex I of respiratory chain is inhibited by

* Site I: This involves the transfer of electrons from NADH-CoQ. Obviously, this step is omitted by succinic dehydrogenase whose FADH2 prosthetic group transfers its electrons directly to CoQ bypassing NADH. This step is blocked by piericidin, rotenone, amobarbital, ceain drugs like chlorpromazine, guanethidine. Site-I (Complex-I) * Rotenone: A fish poison and also insecticide. Inhibits transfer of electrons through complex-I-NADH-Q-reductase. * Amobarbital (Amytal) and Secobarbital: Inhibits electron transfer through NADH-Q reductase. * Piericidin A: An antibiotic. Blocks electron transfer by competing with CoQ. * Drugs: Chlorpromazine and hypotensive drug like guanethidine.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 143


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


Question: Total number of dehydrogenases in Kreb's cycle

There are 4 dehydrogenase in TCA cycle :-

(i) Isocitrate dehydrogenase, (ii) α -ketoglutarate dehydrogenase, (iii) Succinate dehydrogenase, (iv) Malate
dehydrogenase.


Question: Sterols are metabolized to

Vitamin D is derived from 7-dehydrocholesterol by the action of UV radiations 7 dehydrocholesterol, an intermediate of a minor pathway of cholesterol synthesis The cis double bond is isomerized to a trans double bond to give rise to vitamin D3 or cholecalciferol Ref: DM Vasudevan, 7th edition, page no: 469


Question: Triplex DNA is due to

Triple-stranded DNA is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In this structure, one strand binds to a B-form DNA double helix through Hoogsteen or reversed Hoogsteen hydrogen bonds. For example, a nucleobase T binds to a Watson-Crick base-pairing of T-A by Hoogsteen hydrogen bonds between an AxT pair (x represents a Hoogsteen base pair). An N-3 protonated cytosine, represented as C+, can also form a base-triplet with a C-G pair through the Hoogsteen base-pairing of an GxC+. Thus, the triple-helical DNAs using these Hoogsteen pairings consist of two homopyrimidines and one homopurine, and the homopyrimidine third strand is parallel to the homopurine strand.


Question: Triacylglycerol synthesis is enhanced by

TG stores in the body is continually undergoing (a) Esterification (synthesis) and (b) Lipolysis (breakdown).These two processes are not the forward and reverse processes of the same reaction. They are entirely differentMany of the nutritional, metabolic and hormonal factors regulate either of these two mechanisms, i.e. esterification and lipolysis. Resultant of these two processes determine the magnitude of free fatty acid pool in adipose tissue and this, in turn, will determine the level of free fatty acid (FFA) circulating in the blood.I. Esterification (Synthesis of TG) In adipose tissue, for TG synthesis, two substrates are required:Acyl-CoAa-Glycero-PFor detailed steps, see the biosynthesis of TG.1. Sources of Acyl-CoASources of FFA in blood are:Dietary,Synthesis of FA (palmitic acid) from acetyl-CoA 'de novo' synthesis (extramitochondrial). Fuher elongation to form other fatty acids in microsomes.Acyl-CoA obtained from lipolysis taking place in adipose tissue (FFA-Pool No. 1).FFA obtained from lipolysis of TG of circulating chylomicrons and VLDL by lipoprotein lipase enzyme present in capillary wall (FFA-Pool No.2. Which are taken up by adipose tissue. 2. Source of a-Glycerol-PMainly two:Conversion of glycerol to a-Glycero-P by the enzyme Glycerokinase in presence of ATP.The other source is from glucose oxidation. Dihydroxyacetone-P is conveed to a-Glycero-P. The enzyme glycerol kinase is practically absent in adipose tissue. If any glycerokinase is present, it has verylow activity. Hence, glycerol produced by lipolysis in adipose tissue cannot be utilised for provision of a-Glycero-P and thus, glycerol passes into the blood,from where it is taken up by the liver, kidney and other tissues which possess glycerokinase and is utilised for gluconeogenesis. Thus, for provision of a-Glycero-P in adipose tissue for TG synthesis, the tissue is dependent on a supply of glucose and glycolysis.II. Lipolysis (Breakdown of TG)TG in adipose tissue undergoes hydrolysis by a hormone-sensitive TG lipase enzyme to form free fatty acids and glycerol.Adipolytic lipases are three:Hormone-sensitive triacyl glycerol lipase: Key regulating enzyme.Two others are not hormone-sensitive:Diacyl glycerol lipaseMonoacyl glycerol lipaseThese lipases are distinct from lipoprotein lipase that catalyses lipoprotein TG (Present in chylomicrons and VLDL) hydrolysis before it is taken up by extrahepatictissues. The free fatty acids formed by lipolysis can be reconveed in the tissue to acyl-CoA by Acyl-CoA synthase and re-esterified with a-Glycero-P to form TG. Thus, there is a continuous cycle of lipolysis and reesterification within the tissue. NoteWhen the rate of re-esterification is less than rate of lipolysis, FFA accumulates and diffuses into the plasma where it raises the level of FFA | in plasma.Effect of glucose: Under conditions of adequate nutritional intake or when utilisation of glucose by adipose tissue is increased, then more a-Glycero-P will be available. Re-esterification will be greater than lipolysis; as a result, FFA outflow decreases and plasma FFA| level falls. In vitro studies have shown that release of glycerolcontinues; that means lipolysis continues. Hence, effect of glucose in reducing plasma FFA level is not mediated by decreasing the rate of lipolysis. It proves that the effect is due to the provision of a-Glycero-P from glycolysis, which enhances esterification.Adipose tissue metabolism in diabetes mellitus and in starvation: In diabetes mellitus and in starvation,availability of glucose in adipose tissue is grossly reduced, resulting to lack of a-Glycero-P. Thus, the rate of re-esterification is decreased|. Lipolysis is greater thanre-esterification, resulting to the accumulation of FFA and increase in plasma FFA level.Ref: M.N. Chatterjee - Textbook of Biochemistry, 8th edition, page no: 400-402


Question: Transamination of pyruvate and glutamic acid leads to the formation of

Transamination of pyruvate and glutamic acid (or glutamate) 1/t formation of alanine and a-keto (oxo) glutarate.


Question: Frame shift mutation is caused by

Insertion and deletion causes Frame shift mutation.


Question: Major component of DNA

DNA is a polymer of deoxyribonucleotides.