Question: Northern Blot is used to detect

Southern Blot - DNA
Northern Blot - RNA
Western Blot - Proteins.


Question: NADPH is used in

FATTY ACID SYNTHESIS Materials Required for the SynthesisEnzymes-Fatty acid synthase, a multienzyme complex-Acetyl-CoA carboxylase, also a multienzyme complexCoenzymes and cofactors: Biotin, NADPH, Mn++CO2: Source of CO2 is bicarbonateATP: For energyFirst reaction (reduction): The keto-acyl group is reduced to hydroxy group (-OH) to form "b-OH butyryl-ACP" catalyzed by the enzyme "keto-acyl reductase". Second reaction (dehydration): A molecule of H2O is removed from "b-OH-butyryl-ACP" to form "a, bunsaturated butyryl-ACP" (also called crotonyl-ACP), catalyzed by the enzyme "b-OH-acyl dehydratase". Third reaction (reduction): The third and final reduction is catalyzed by "enoyl-reductase" using NADPH + H+, as a result, the double bond is saturated to form "butyryl-ACP" (4 carbon). All the above three reactions occur on "Pan-SH" of monomer II.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition, Page no: 417


Question: Disulphide bond is seen between

Disulphide bonds: These are formed between two cysteine residues. They are strong, high energy covalent bonds.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 89


Question: Cyanide is toxic because it

Site-III (Complex IV) (CYTOCHROME OXIDASE ) * Cyanide Blocks electron transfer from cyt b to c1 Inhibits terminal * H2S * Azide transfer of electrons to molecular O2 * Co (Carbon monoxide): Inhibits Cyt. oxidase by combining with O2 binding site. It can be reversed by illumination with light.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition


Question: Casein, the milk protein is

Phosphoproteins: These contain phosphorus. Casein of milk and vitellin of egg yolk are examples. The phosphoric acid is esterified to the hydroxyl groups of serine and threonine residues of proteins.
Reference: Vasudevan 7th  ed, pg 43


Question: Ammonia is detoxified in brain by formation of

The transpo form of Ammonia in blood and from Brain is Glutamine. From muscles, it is Alanine. The answer is not glutamate because free ammonia is trapped by glutamine Glutamate is formed transamination of amino acids, not from free ammonia.


Question: Histidine is the most impoant amino acid for buffering in normal conditions because

Ans. is 'c' i.e., PKa value is closer to pH Maximal buffering capacity occurs at pH equal to pka of buffer.Therefore, to work as a best buffer at physiological pH amino acid should have pka value close to physiological pH (7.4).Amino acids can have buffering action due to three ionizable groups :a-carboxyl group :- Different amino acids have pka value of a-carboxyl group between 3.5-4. So, carboxyl group of amino acids has maximum buffering capacity between pH 3.5-4.a-amino group :- Different amino acids have pka value of a-amino group between 8.0-9.0. Thus, a-amino group has maximum buffering capacity between pH 8.0-9.0.Special ionizable group (in some amino acids):- Among special ionizable group of amino acids, imidazole group of histidine has pka value 6.5-7.4, which is closest to physiological pH. Hence, histidine (due to imidazole group) has maximum buffering capacity at physiologial pH.


Question: Succinate dehydrogenase is inhibited by

Succinate is dehydrogenated to fumarate, an unsaturated dicarboxylic acid, by succinate dehydrogenase (step 6, Fig.18.2). The hydrogen atoms are accepted by FAD. The FADH2 then enters into ETC to generate ATPs. The enzyme is a flavoprotein. The succinate dehydrogenase is competitively inhibited by malonateRef: DM Vasudevan, Page no: 219


Question: Creatinine is synthesized from

Creatine & CreatinineCreatinine is formed in muscle from creatine phosphate by irreversible, nonenzymatic dehydration, and loss of phosphate. Since the 24-hour urinary excretion of creatinine is propoionate to muscle mass, it provides a measure of whether a complete 24-hour urine specimen has been collected. Glycine, arginine, and methionine all paicipate in creatine biosynthesis. Synthesis of creatine is completed by methylation of guanidinoacetate by S-adenosylmethionine.Ref: Harper&;s Biochemistry; 30th edition; Chapter 30; Conversion of Amino Acids to Specialized Products


Question: The primary defect in Xeroderma pigmentosa is

In xerodenna pigmentosa; nucleotide excision repair of damaged DNA is defective due to formation of TT dimers.


Question: In DNA, Cytosine is passed with

In DNA , Cytosine pairs with Guanine and Thymine pairs with Adenine. Ref : DM.VASUDEVAN.TEXTBOOK ; SEVENTH EDITION ; PAGE NO : 560


Question: Neutral amino acid is

Classification of aminoacids based on side chain and charges. Acidic amino acids (with negative charge) Basic amino acids (with positive charge) Neutal aminoacids (having non-polar side chains )(hydrophobic) Neutral amino acids (having polar side chains )(hydropilic) Tyrosine Lysine Alanine Aspaic acid Arginine Valine Serine Glutamic acid Histidine Leucine Threonine Isoleucine Cysteine Methionine Glutamine Phenylalanine Asparagine Tryptophan Proline REFERENCE: DM VASUDEVAN TEXTBOOK EIGHTH EDITION ;Page no:27 t


Question: Increased uric acid level in plasma is due to

Salvage pathway ensures the recycling of purines formed by the degradation of nucleotides.Some reactions will consume PRPP and produce more nucleotides will inhibit the enzymes thus salvage pathway is blocked.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 567


Question: Cholesterol present in LDL

On accumulation in the cell inhibits replenishment of LDL receptors

If LDL cholesterol is increased inside the cell, it down regulates LDL receptors so that further uptake is inhibited.
HDL cholesterol is the cholesterol that is removed from peripheral tissues; LDL cholesterol represents the cholesterol which is to be delivered to peripheral tissues.
LDL binds to LDL receptors and whole LDL particle is endocytosed by receptor mediated endocytosis via clathrin-coated pits (not by diffusion:- diffusion and endocytosis are different processes).
Intracellular cholesterol activates intracellular enzyme acyl-CoA cholesterol acyl transferase (ACAT).

Represents primarily cholesterol that is being removed from peripheral cells

Binds to a receptor and diffuses across the cell membrane

When enters a cell, suppresses activity of acyl-CoA; cholesterol acytransferase ACAT


Question: Vit B1 is a cofactor for

Vit B1 is a cofactor for Transketolase. Transketolase: The second group of enzymes that use TPP as co-enzyme are the transketolases, in the hexose monophosphate shunt pathway of glucose the main role is in carbohydrate metabolism Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 467


Question: The structural proteins are involved in maintaining the shape of a cell or in the formation of matrices in the body. The shape of these proteins is

Collagen is the most abundant of the fibrous proteins that constitute more than 25% of the protein mass in the human body. Other prominent fibrous proteins include keratin and myosin. These fibrous proteins represent a primary source of structural strength for cells (i.e., the cytoskeleton) and tissues.Ref: Harper 28th Ed. Page-40, Harper 27th Ed. Page: 38


Question: Chitin held together by

(P (1-4) gluycosidic bonds) (22-US 3rd)CHITIN - is composed of N-acetyl-D-glucosamine units held together by p (1 - 4) glycosidic-bondsStarch* Amylose - a (1-4) glycosidic linkage* Amylopectin - a (l- 6) glycosidic bonds at the branching points and a (l- 4) linkages* Amylase - acts specifically on a (1-4) glycosidic bondsGlycogen - Glucose is the repeating unit in glycogen joined together by a (1-4) glycosidic bonds and a (1-6) glycosidic bonds at branching points.Cellulose - composed of b-D-glucose units linked by b (1- 4) glycosidic bondsIn isomaltose, the glucose units are held together by a (1- 6) glycosidic linkage


Question: Vitamin B12 is absorbed in the


Question: Xeroderma pigmentation is caused due to a group of closely related abnormalities in

Autosomal recessive conditionThere are seven xeroderma pigmentosum genes necessary for NER mechanism in humans Mutation in any of them lead to the condition XPRef: DM VASUDEVAN 7th edition, page no: 584


Question: Glucose transpoer in myocyte stimulated by insulin is

GLUT 4 is the insulin-regulated glucose transpoer found in adipose tissue and striated muscleinsulin induces rapid increase in the uptake of glucose by inducing the translocation of GLUT 4 from these vesicles to the plasma membraneRef: DM Vasudevan, 7th edition, page no: 108


Question: Fatty liver in Kwashiorkor occurs due to

Fatty liver is seen in some cases of kwashiorkor, but not in marasmus. Fatty liver is due to decreased lipoprotein synthesis.Ref: DM Vasudevan, page no: 440

Lack of substrates for protein synthesis in liver

Lack of substrates for gluconeogenesis in liver


Question: Coenzyme required for transketolase reaction is

Transketolase transfers the two-carbon unit comprising carbons 1 and 2 of a ketose onto the aldehyde carbon of an aldose sugar. It, therefore, effects the conversion of a ketose sugar into an aldose with two carbons less and an aldose sugar into a ketose with two carbons more. The reaction requires Mg2+ and thiamin diphosphate (vitamin B1) as the coenzyme. Measurement of erythrocyte transketolase and its activation by thiamin diphosphate provides an index of vitamin B1 nutritional status.Ref: Harper&;s Biochemistry; 30th edition; Chapter 20; The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism


Question: Reduction potential of potassium is


Question: Biuret test is used for detection of


Question: Mousy (musty) odour of urine is feature of

Ans. a (Phenylketonuria) (Ref. Harper's Biochemistry 25th/pg. 335,815)INBORN ERRORS OF AMINO ACID METABOLISM ASSOCIATED WITH ABNORMAL ODORInborn error of metabolismUrine odor1Glutaric acidemia (type II)Sweaty feet, acrid2HawkinsinuriaSwimming pool3Isovaleric acidemiaSweaty feet, acrid4Maple syrup urine diseaseMaple syrup/Burnt sugar5HypermethioninemiaBoiled cabbage6Multiple carboxylase deficiencyTomcat urine7Oasthouse urine diseaseHops-like8PhenylketonuriaMousy or musty9TrimethylaminuriaRotting fish10TyrosinemiaBoiled cabbage, rancid butterPHENYLKETONURIA# impaired ability to convert phenylalanine to tyrosine fall into three broad groups:- Classic Phenylketonuria or Type I - Phenylalanemia -^Defect in phenylalanine hydroxylase- Phenylalanemia type II and III - defect in Dihydrobiopterin reductase- Type IV and V defect - in Dihydrobiopterin biosynthesis.# Catabolites phenyl acetate and others are excreted in urine and responsible for "Mousy odor"# C/F:- Mental retardation- Seizures- Psychoses- Eczema- Mousy odor# Diagnosis By:- Guthrie's test (Microbiological test, phenylalanine is necessary for growth of Bacillus subtilis)Q- 10% ferric chloride test: on fresh urine: Emerald green color Q.- Fluorometric assay- Dinitrophenylhydrazine: yellow ppt. with fresh or old urine.# T/t:- Diet restriction of phenylalanine but not completely- As it is necessary for normal growth and may be terminal by age 6 yrs.- MR can be prevented if diet restriction is initiated within few weeks after birth.MAPLE SYRUP URINE DISEASE (BRANCHED-CHAIN KETONURIA)# Absence of alpha-keto acid decarboxylase# Leads to defect in metabolism of Branched-chain amino acid--leucins, isoleucine and valine# "Maple syrup or Burnt sugar" odor of urine# FeC12 test gives Navy Blue colorISOVALERIC ACIDAEMIA:# Sweety foot syndrome# Deficiency of Isovaleryl CoA dehydrogenase.# C/F-- "Cheesy odor" of breath and body fluids.


Question: Phospholipid is

Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 46


Question: Vitamin B6 deficiency cause increased excretion of

Vit B6 deficiency causes increased excretion of Xanthurenic acid.Pyridoxal phosphate is required for the synthesis of niacin from tryptophan (one vitamin is necessary for synthesis of another vitamin) (Figs17.8 and 17.9). 3-hydroxy kynurenine - 3-hydroxy anthranilic acid (Enzyme Kynureninase). Kynureninase is a PLP dependent enzyme. Hence in vitamin B6 deficiency niacin production is less. Moreover, kynurenine cannot be conveed fuher, which is metabolized to xanthurenic acid and excreted through urine. The metabolic disorders which respond to vitamin B6 therapy are xanthurenic aciduria and homocystinuria.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 397


Question: HMG Co A production in liver is inhibited by


Question: In E.coli structural gene of lac operon is stimulated in

JACOB and MONAD theory was based on the observation on lactose metabolism in E.coli Cell grown in glucose medium does not contain beta-galactosidase But when cells are transferred to medium containing only lactose, then the enzyme level in the cell increases several thousand foldsRef: DM Vasudevan, 7th edition, page no: 617

Presence of glucose and absence of lactose

Presence of lactose and absence of glucose


Question: Wilson's disease is characterized by the deposition of one of the following minerals in the tissue

(B) Cu # Wilsons' disease (hepatolenticular degeneration):# A rare disorder of abnormal copper metabolism and is characterized by the following manifestations:> Copper is deposited in abnormal amounts in liver and lenticular nucleus of brain.> This may lead to hepatic cirrhosis and brain necrosis> Low levels of copper and ceruloplasmin in plasma with increased excretion of copper in urine.> Copper deposition in kidney causes renal damage.> This leads to increased excretion of amino acids, glucose, peptides and hemoglobin in urine.> Intestinal absorption of copper is very high, about 4-6 times higher than normal.


Question: The nitrogen content in 50 gm of a typical dietary protein is most likely to be


Question: The collagen triple helix structure is not found in

Like most secreted proteins, collagen is synthesized on ribosomes in a precursor form, preprocollagen, which contains a leader or signal sequence that directs the polypeptide chain into the lumen of the endoplasmic reticulum. As it enters the endoplasmic reticulum, this leader sequence is enzymatically removed.Following secretion from the cell by way of the Golgi apparatus, extracellular enzymes called procollagen aminoproteinase and procollagen carboxyproteinase remove the extension peptides at the amino and carboxyl terminal ends, respectively forming the monomeric units of collagen, termed tropocollagen. Newly synthesized proteins are soed first according to the soing signals available in the proteins. Then they are packaged into transpo vesicles having different types of coat proteins. Finally they are transpoed into various destinations; this is an energy dependent process Ref: Harper's Illustrated Biochemistry, 26th edition, page no: 535 Ref: Textbook of Biochemistry for Medical Students, 7E (DM Vasudevan)(2013)Pg no 12.


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

We will illustrate, in addition, how biochemical measurements can pinpoint a disorder and allow one to determine which enzyme is functioning improperly.a. Mouth(1). Salivary glands produce a-amylase, which cleaves a-1,4 bonds between glucose residues in dietary starch. (Pancreatic a-amylase catalyzes the same reaction.)b. Stomach(1). Chief cells produce the proteolytic enzyme pepsin, as its inactive precursor pepsinogen. Pepsin digests proteins.(2). Parietal cells produce hydrochloric acid (HCl) and intrinsic factor.(a). HCl causes pepsinogen (the precursor of pepsin) to cleave itself (autocatalysis), producing pepsin.(b). Intrinsic factor binds dietary vitamin B12 and aids in its absorption.(c). Vitamin B12 is the cofactor for the conversion of homocysteine to methionine and methyl malonyl-CoA to succinyl-CoAc. Gallbladder(1). Bile salts, synthesized in the liver from cholesterol, pass through the gallbladder into the intestine, where they aid in lipid digestion.(2). Bilirubin diglucuronide, produced in the liver from bilirubin (the excretory product of heme degradation), passes through the gallbladder into the intestine.d. Pancreas(1). The pancreas produces bicarbonate (HCO3- ), which neutralizes stomach acid as it enters the intestinal lumen. The subsequent increase in pH in the lumen allows more extensive ionization of bile salts (so they serve as better detergents) and increases the activity of digestive enzymes.(2). The pancreas produces digestive enzymes (e.g., trypsin, chymotrypsin, the carboxypeptidases, elastase, a-amylase, lipase).(3). The B (or b) cells of the endocrine pancreas produce insulin (the hormone that stimulates the storage of fuels in the fed state) and the A (or a) cells produce glucagon (the hormone that stimulates the release of stored fuels during fasting).e. Intestine(1). The enzymes from the exocrine pancreas digest food in the intestinal lumen.(2). The intestinal digestive enzymes are bound to the brush borders of intestinal epithelial cells (aminopeptidases, dipeptidases and tripeptidases, lactase, sucrase, maltases, and isomaltases).(3). The absorption of digestive products occurs through the intestinal epithelial cells.(4). The intestinal epithelial cells produce chylomicrons from the digestive products of dietary fat (fatty acids and 2-monoacylglycerols) and secrete the chylomicrons into the lymph.(5). Most bile salts are resorbed in the ileum and recycled by the liver. Only 5% are excreted in the feces. This excretion of bile salts, along with cholesterol secreted by the liver into the gut via the gallbladder, is the major means by which the body disposes of the cholesterol ring structure (sterol nucleus).f. Liver (the enzymic regulation of liver function is summarized in Tables below)(1). Functions of the liver include:(a). Storage of glycogen produced from dietary carbohydrate.(b). Synthesis of very low-density lipoprotein (VLDL), mainly from dietary carbohydrate.(c). Production of high-density lipoprotein, which transfers CII and E apolipoproteins to chylomicrons and VLDL, converts cholesterol to cholesterol esters (via the lecithin-cholesterol acyltransferase reaction), and reduces blood by which cholesterol and cholesterol esters are transported from tissues to the liver (reverse cholesterol transport).(d). Maintenance of blood glucose levels during fasting via glycogenolysis and gluconeogenesis.(e). Production of urea from nitrogen derived, in part, from amino acids because they are being converted to glucose (via gluconeogenesis) during fasting.(f). Production of ketone bodies from fatty acids derived from lipolysis of adipose triacylglycerols during fasting.(g). Synthesis of cholesterol (which is also made in other tissues).(h). Conversion of cholesterol to bile salts.(i). Production of many blood proteins (e.g., albumin, blood-clotting proteins).(j). Production of purines and pyrimidines, which are transported to other tissues via red blood cells.(k). Degradation of purines (to uric acid) and pyrimidines (to CO2 , H2 O, and ammonia).(l). Oxidation of drugs and other toxic compounds via the cytochrome P450 system.(m). Conjugation of bilirubin and excretion of bilirubin diglucuronide into the bile.(n). Oxidation of alcohol via alcohol and acetaldehyde dehydrogenases and the microsomal ethanol-oxidizing system (MEOS).(o). Synthesis of creatine (from guanidinoacetate), which is used to produce creatine phosphate, mainly in the muscle and brain.(p). Conversion of dietary fructose to glycolytic intermediates.(2). If liver cell function is compromised (e.g., in viral hepatitis or alcoholic cirrhosis):(a). NH4+ , which is toxic (particularly to the central nervous system), increases in the blood.(b). The BUN level decreases because the liver has a decreased capacity to produce urea.(c). Blood glucose decreases because of decreased glycogenolysis and gluconeogenesis.(d). Blood cholesterol levels decrease owing to an inability to produce and secrete VLDL.(e). The production of bile salts decreases.(f). Bilirubin levels increase in the body (causing jaundice) because of reduced conjugation with glucuronic acid.(g). Lysis of damaged liver cells allows enzymes to leak into the blood.1. Lactate dehydrogenase increases.2. Alanine aminotransferase increases.3. Aspartate aminotransferase increases.4. Alkaline phosphatase increases.(h). Chronic liver problems result in decreased protein synthesis.1. Serum proteins (e.g., albumin) decrease.2. VLDL production decreases because of decreased apolipoprotein B-100 and triacylglycerols accumulate in the liver. A fatty liver results.g. Brain(1). Glucose is the major fuel for the brain.(2). The brain can use ketone bodies, but only after 3 to 5 days of fasting when blood ketone body levels are elevated.(3). The brain needs energy to think (i.e., memory involves RNA synthesis), conduct nerve impulses, synthesize neurotransmitters, and so on.h. Red blood cells(1). Red blood cells lack mitochondria, so they have no TCA cycle, b-oxidation of fatty acids, electron transport chain, and other pathways that occur in the mitochondria.(2). Glucose is the major fuel for red blood cells.(a). Glucose is converted to pyruvate and lactate.(3). Red blood cells carry bases and nucleosides from the liver to other tissues.(4). The major function of red blood cells is to carry O2 from the lungs to the tissues and to aid in the return of CO2 from the tissues to the lungs.i. Adipose tissue(1). The major fuel of adipose tissue is glucose.(2). Insulin stimulates the transport of glucose into adipose cells.(3). The function of adipose tissue is to store triacylglycerol in the fed state and release it (via lipolysis) during fasting.(a). In the fed state, insulin stimulates the synthesis and secretion of lipoprotein lipase (LPL), which degrades the triacylglycerols of chylomicrons and VLDL in the capillaries. Fatty acids from these lipoproteins enter adipose cells and are converted to triacylglycerols and stored. Glucose provides the glycerol moiety. (Glycerol is not used because adipose cells lack glycerol kinase.)(b). During fasting, adipocyte triglyceride lipase and hormone-sensitive lipase (phosphorylated and activated via a cAMP-mediated mechanism) initiate lipolysis in adipose cells.j. Muscle(1). Muscle uses all fuels that are available (glycogen stores, and fatty acids, glucose, ketone bodies, lactate, and amino acids from the blood) to obtain energy for contraction.(2). During fasting, muscle protein is degraded to provide amino acids (particularly alanine) for gluconeogenesis.(3). Creatine phosphate transports high-energy phosphate from the mitochondria to actinomyosin fibers and provides ATP for muscle contraction.(4). Creatinine is produced nonenzymatically from creatine phosphate, and a constant amount (dependent on the body muscle mass) is released into the blood each day and excreted by the kidneys.(5). Muscle glycogen phosphorylase differs from liver phosphorylase but catalyzes the same reaction (glycogen+Pi-glucose-1-phosphate).(6). Insulin stimulates the transport of glucose into muscle cells.k. Heart(1). The heart is a specialized muscle that uses all fuels from the blood.(2). The muscle-brain (MB) isozyme of CK is found in heart muscle. Its release can be used to monitor a heart attackl. Kidney(1). The kidney excretes substances from the body via the urine, including urea (produced by the urea cycle in the liver), uric acid (from purine degradation), creatinine (from creatine phosphate), NH4+ (from glutamine via glutaminase), H2SO4 (produced from the sulfur of cysteine and methionine), and phosphoric acid.(2). Daily creatinine excretion is constant and depends on the body muscle mass. It is used as a measure of kidney function (the creatinine-clearance rate).(3). Glutaminase action increases during acidosis and produces NH3 , which enters the urine and reacts with H+ to form NH4+ . NH4+ buffers the urine and removes acid (H+) from the body.(4). Uric acid excretion is inhibited by lead (Pb) and metabolic acids (ketone bodies and lactic acid). High blood uric acid can result in gout. Gout can be caused either by increased production or by decreased excretion of uric acid. Deficiency of the base salvage enzyme hypoxanthine guanine phosphoribosyl transferase in Lesch-Nyhan syndrome results in increased production of uric acid.(5). Kidney dysfunction can lead to increased BUN, creatinine, and uric acid in the blood and decreased levels of these compounds in the urine.(6). During ketoacidosis, ketone bodies are excreted by the kidney, and during lactic acidosis, lactic acid is excreted.(7). Elevated blood glucose levels (over 180 mg/dL) in DM results in the excretion of glucose in the urine.Intrinsic factor is required for the absorption of dietary vitamin B12 . Lack of B12 (or folate) results in a megaloblastic anemia. In a B12 deficiency, irreversible neurologic problems (due to demyelination) also occur. When decreased intrinsic factor causes a B12 deficiency, the condition is called pernicious anemia. An iron-deficiency anemia is characterized by small, pale RBCs. The lack of iron reduces the synthesis of heme, so the red cells cannot carry as much oxygen (which gives them the pale color). The cells are small in order to maximize the concentration of hemoglobin present in the cells. Hemolytic anemia occurs when the red cell membrane fragments, which can occur with pyruvate kinase deficiencies or a lack of glucose-6-phosphate dehydrogenase activity (which results in reduced NADPH levels). Sickle cell anemia is caused by a point mutation in the b-globin gene, substituting a valine for a glutamic acid.When Blood Sugar Increases:When Blood Sugar Decreases:Insulin is released, which leads to the dephosphorylation of:Glucagon is released, which leads to the phosphorylation of:PFK-2 (kinase activity now active)PFK-2 (phosphatase activity now active)Pyruvate kinase (now active)Pyruvate kinase (now inactive)Glycogen synthase (now active)Glycogen synthase (now inactive)Phosphorylase kinase (now inactive)Phosphorylase kinase (now active)Glycogen phosphorylase (now inactive)Glycogen phosphorylase (now active)Pyruvate dehydrogenase (now active)Pyruvate dehydrogenase (now inactive)Acetyl-CoA carboxylase (now active)Acetyl-CoA carboxylase (now inactive)Which leads to activeGlycolysis GlycogenolysisFatty acid synthesisFatty acid oxidationGlycogen synthesisGluconeogenesis Liver Enzymes Regulated by Activation/InhibitionEnzymeActivated byState in Which ActivePhosphofructokinase 1Fructose 2,6-bisP, AMPFedPyruvate carboxylaseAcetyl-CoAFed and fastingAcetyl-CoA carboxylaseCitrateFedCarnitine palmitoyltransferase ILoss of inhibitor (malonyl-CoA)FastingLiver Enzymes Regulated by Phosphorylation/DephosphorylationEnzymeActive formState in Which ActiveGlycogen synthaseDephosphorylatedFedPhosphorylase kinasePhosphorylatedFastingGlycogen phosphorylasePhosphorylatedFastingPhosphofructokinase- 2/fructose 2,6-bisphosphatase (acts as a kinase, increasing fructose2,6-bisP levels)DephosphorylatedFedPhosphofructokinase-2/fructose 2,6-bisphosphatase (acts as aphosphatase, decreasing fructose 2,6-bisP levels)PhosphorylatedFastingPyruvate kinaseDephosphorylatedFedPyruvate dehydrogenaseDephosphorylatedFed


Question: Protein efficiency ratio is

A. i.e. (Gain in weight / Protein consumed) (702- Rana Shinde 7th) (512 - U. satyanarayan 3rd)1. PROTEIN EFFICIENCY RATIO (PER) - consists of feeding weaning (21 days old) albino rats with a 10% test protein diet and recording the gain in body weight for a period of 4 weeks.Gain in weight of young animals per unit weight ofprotein consumed**PER =Gain in body weight (g)Protein consumed (g)The PER for egg protein is 4.5 : for milk protein 3.0 for rice protein 2.22. BIOLOGICAL VALUE - defined % of absorbed nitrogen retained by bodyBV =Nitrogen retained-----------Nitrogen absorbedx 1003. NET - Protein Utilization (NPU) - defined % of food Nitrogen that is retained in the bodyNPU =Digestibility Cofficient x Biological valueProtein intake (gm)4. CHEMICAL SCORE - based on the chemical analysis of the protein for the composition of essential amino acids which is then compared with a reference protein (usually egg protein)Chemical score =mg of the limiting amino acid/g. test proteinmg. of the same amino acid/g.egg proteinx 100

Product of digestibility coefficient and biological value divided by 100

Percentage of nitrogen retained out of nitrogen absorbed

Percentage of protein absorbed after digestion


Question: Most abundant in bone

Hydroxyproline is catabolized more or less similar to proline. It is confer strength to fibrous proteins like collagen , elastin, keratin.etc.In vitamin C deficiency hydroxyproline synthesis is reduced , causing strength of fibers , leading to scurvy. The excretion of hydroxyproline in urine is increased in tumours infiltrating bones and in diabetic patients due to enhanced rate of protein catabolism. REFERENCE: DM.VASUDEVAN.TEXTBOOK SEVENTH EDITION ;PAGE NO : 244


Question: Vitamin B12 and folic acid supplementation in megaloblastic anemia leads to the improvement of anemia due to

Deficiency of folic acid Reduced DNA Synthesis because THF derivatives are involved in purine synthesis and thymidylate Synthesis Megaloblastic Anemia Vitamin B12 deficiency and Folate deficiency can lead to this condition In Vitamin B12 deficiency Megaloblastic anemia is due to folate trap ref DM Vasudevan 8th ed page 476


Question: One of the following enzymes is not a protein

A ribozyme is a ribonucleic acid (RNA) enzyme that catalyzes a chemical reaction. The ribozyme catalyses specific reactions in a similar way to that of protein enzymes.
Also called catalytic RNA, ribozymes are found in the ribosome where they join amino acids together to form protein chains. Ribozymes also play a role in other vital reactions such as RNA splicing, transfer RNA biosynthesis, and viral replication.


Question: Fructose is transpoed by

GluT5 is present in small intestine, testis, sperms, kidney. :: fructose transpoer; poor ability to transpo glucose.Ref: DM Vasudevan, 7th edition, page no: 106


Question: Membrane fluidity is increased by

The cholesterol content of the membrane alters the fluidity of the membrane. When cholesterol concentration increases, the membrane becomes less fluid on the outer surface, but more fluid in the hydrophobic core. The effect of cholesterol on membrane fluidity is different at different temperatures. At temperature below the Tm cholesterol, in-7 creases fluidity and thereby permeability of the membrane. At temperatures above the Tm, cholesterol decreases fluidity. Linoleic acid increases the membrane fluidity.Ref: DM Vasudevan, page no: 11


Question: RNA polymerase does not require

RNA Polymerases Mammalian : RNAP type II or B is the main enzyme synthesizing mRNAs.It is inhibited by alpha amanitin. Amanitin blocks the translocation of RNAPduring mRNA synthesis. SnRNA and mRNA are also synthesized by the same RNAP B. RNAP has two large and 12 smaller subunits. Phosphorylation activates RNAP II The templte strand is transcribed to give rise to mRNA. BACTERIAL : BacterialRNAP enzyme contains two alpha , two beta subunits ,one omega subunit and ine sigma factor and two zinc molecules. Beta subunit fixes at the initiation site. The sigma factor recognizes the promoter site and increases the affinity if the holoenzyme to the promoter site. REF : DM VASUDEVAN TEXTBOOK ; 7th EDITION ; Page no :589


Question: Trinucleotide repeat is seen in

(A) Fragile X syndrome # Trinucleotide repeat disorder> Trinucleotide repeat disorders (also known as trinucleotide repeat expansion disorders, triplet repeat expansion disorders or codon reiteration disorders) are a set of genetic disorders caused by trinucleotide repeats in certain genes exceeding the normal, stable, threshold, which differs per gene.> The mutation is a subset of unstable micro satellite repeats that occur throughout all genomic sequences.> If the repeat is present in a healthy gene, a dynamic mutation may increase the repeat count and result in a defective gene.> The first triplet disease to be identified was fragile X syndrome that has since been mapped to the long arm of the X chromosome.> At this point, there are from 230 to 4000 CGG repeats in the gene that causes fragile X syndrome in these patients, as compared with 60 to 230 repeats in carriers and 5 to 54 repeats in normal persons.> The chromosomal instability resulting from this trinucleotide expansion presents clinically as mental retardation, distinctive facial features, and macroorchidism in males.> The second, related DNA-triplet repeat disease, fragile X-E syndrome, was also identified on the X chromosome, but was found to be the result of an expanded GCC repeat.> Identifying trinucleotide repeats as the basis of disease has brought clarity to our understanding of a complex set of inherited neurological diseases.


Question: Enzyme does not act by

Enzyme decreases the activation energy & thus they increase the rate of reaction. Mostly in Enzyme-Substrate (ES) interactions, non covalent interactions are formed (Hydrogen, Hydrophobic & Ionic bonds). Gibb's Free Energy graph for enzyme catalyzed and enzyme uncatalyzed reaction. On X- axis, reaction progress taken (i.e. S getting conveed to P). For any spontaneous reaction, S has more free energy as compared to P. For S to be conveed to P, first S has to acquire Activation energy (DG uncatalyzed) and reach high energy state (Transition state). Only then it can be conveed to P.


Question: Least energy producing cycle

Ans. is 'c' i.e.,HMP shunt HMP shunt does not produce energy.HMP shunt is paicularly impoant for two purposes :-Synthesis of ribose for nucleotide and nucleic acid formation.Formation of NADPH which plays impoant role in several other biological processes, e.g. synthesis of fatty acids, cholesterol, steroid hormones and neurotransmitters.


Question: Unwinding of DNA during replication is done by

Helicases are enzymes that bind and may even remodel nucleic acid or nucleic acid-protein complexes. There are DNA and RNA helicases. DNA helicases are essential during DNA replication because they separate double-stranded DNA into single strands allowing each strand to be copied Ref-Sathyanarayana 4/e


Question: Enzyme activated by covalent phosphorylation is

Glycogen phosphorylase removes glucose as glucose-1-phosphate from glycogen(phosphorolysis). It contains pyridoxal phosphate as a prosthetic group.Ref: DM Vasudevan, 7th edition, page no: 124


Question: Tryptophan gives rise to

Melatonin is synthesised from serotonin which in turn is from tryptophan.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 519


Question: Cofactor for glycogen phosphorylase

Pyridoxal phosphate is an essential cofactor for glycogen phosphorylase.


Question: In TCA cycle, CO2 is released from

During the citric acid cycle, two carbon dioxide molecules are removed in the following reactions: A. Step 3, isocitrate (oxalosuccinate) to alpha-ketoglutarate catalyzed by isocitrate dehydrogenase B. Step 4, alpha-ketoglutarate to succinyl CoA.it is from substrate co2is raised..not from enzymes. They are just catalyzing the reaction.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition, Page no: 219


Question: Urine osmolality in Diabetes insipidus is

Diabetes insipidus is condition characterised by excessive thirst excretion of large amounts of severely diluted urine Those with diabetes insipidus continue to uinate large amount of urine in spite of water deprivation.Ref: DM Vasudevan, 7th edition, page no: 373


Question: Gluconeogenesis in fasting state is stimulated by

Ans. b. Activation of pyruvate carboxylase by acetyl Co-A

Activation of pyruvate kinase by fructose 1, 6-bisphosphate

Stimulation of phosphofructokinase-1 by fructose 2, 6-bisphosphate


Question: Niacin deficiency causes

Deficiency of niacin: A deficiency of niacin causes pellagra, a disease involving the skin, gastrointestinal tract, and CNS. The symptoms of pellagra progress through the three Ds: dermatitis, diarrhoea, dementia--and, if untreated, death. Reference: Lippincott Textbook of Biochemistry pg no. 380


Question: FSH, LH, TSH acts through


Question: Transition temperature of lipid bilayers of cell membranes is increased by

The cholesterol content of the membrane alters the fluidity of the membrane. When cholesterol concentration increases, the membrane becomes less fluid on the outer surface, but more fluid in the hydrophobic core. The effect of cholesterol on membrane fluidity is different at different temperatures. At temperature below the Tm, cholesterol increases fluidity and thereby permeability of the membrane. At temperatures above the Tm, cholesterol decreases fluidity.Ref: DM Vasudevan, page no: 11


Question: Citrullinemia type I results from deficiency of the

(B) Argininosuccinate synthase# Citrullinemia type I (CTLN1) presents as a clinical spectrum that includes an acute neonatal form (the "classic" form), a milder late-onset form, a form without symptoms or hyperammonemia, and a form in which women have onset of severe symptoms during pregnancy or post partum.> Citrullinemia type I results from deficiency of the enzyme argininosuccinate synthase (ASS), the third step in the urea cycle in which citrulline is condensed with aspartate to form argininosuccinic acid.> Untreated individuals with the severe form of citrullinemia type I have hyperammonemia (plasma ammonia concentration 1000- 3000 pmol/L).> Plasma quantitative amino acid analysis shows absence of argininosuccinic acid and concentration of citrulline usually greater than 1000 pmol/L (normal: <50 pmol/L).> Argininosuccinate synthase enzyme activity, measured in fibroblasts, liver, and in all tissues in which ASS is expressed, is decreased.> ASS1 is the only gene in which mutation is known to cause citrullinemia type I.


Question: Scavenger receptors uptake

LOW-DENSITY LIPOPROTEINS (LDL) LDL transpos cholesterol from liver to peripheral tissues. The only apoprotein present in LDL is apo B100. Most of the LDL paicles are derived from VLDL, but a small pa is directly released from liver. The half-life of LDL in blood is about 2 days. Metabolism of LDL and LDL Receptors LDL is taken up by peripheral tissues by receptor-mediated endocytosis. LDL receptors are present on all cells but most abundant in hepatic cells. LDL receptors are located in specialised regions called clathrin-coated pitsBinding of LDL to the receptor is by apo-B-100 and uptake of cholesterol from LDL is a highly regulated process. When the apo-B-100 binds to the apo-B-100 receptor, the receptor-LDL complex is internalised by endocytosis. The endosome vesicle thus formed fuses with lysosomes. The receptor is recycled and returns to the cell surface. The LDL paicle, along with apoproteins and cholesterol ester is hydrolysed by lysosomal hydrolases, forming amino acids and free cholesterol. The free receptors can now return to the membrane surface to bind fuher LDL molecules (Fig. 12.13). Approximately 70% of LDL is degraded in the liver, and the rest in extra-hepatic tissues. For their work on LDL receptors, Michael Brown and Joseph Goldstein were awarded Nobel prize in 1985. Function of LDL About 75% of the plasma cholesterol is incorporated into the LDL paicles. LDL transpos cholesterol from liver to the peripheral tissues. The cholesterol thus liberated in the cell has three major fates: i. It is used for the synthesis of other steroids like steroid hormones. ii. Cholesterol may be incorporated into the membranes. iii. Cholesterol may be esterified to a MUFA by acyl cholesterol acyltransferase (ACAT) for storage. The cellular content of cholesterol regulates fuher endogenous synthesis of cholesterol by regulating HMG CoA reductase.LDL and Clinical Applications LDL concentration in blood has positive correlation with incidence of cardiovascular diseases. A fraction of cholesterol is taken up by macrophages, this is not a regulated pathway. Increased levels of LDL or modification of LDL by glycation (as seen in diabetes mellitus) or oxidation increases the fraction of cholesterol taken up by macrophages. LDL infiltrates through aerial walls and is taken up by macrophages or scavenger cells. This is the staing event of atherosclerosis leading to myocardial infarction (see coronary aery diseases in Chapter 25). When these cells become engorged with cholesterol, foam cells are formed, that get deposited in the subendothelial space triggering formation of atheromatous plaque (see Fig. 25.3). Procoagulant changes are induced in the endothelium resulting in increased chances of thrombosis and coronary aery disease (Fig. 25.4). Since LDL-cholesterol is thus deposited in tissues, the LDL (low-density lipoprotein) variety is called "bad cholesterol" and LDL as "Lethally Dangerous Lipoprotein"Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 153-154


Question: Branching enzyme deficiency is seen in

Type Name Enzyme Deficiency Clinical Features IV Amylopectinosis, Andersen disease Branching enzyme Hepatosplenomegaly Accumulation of polysaccharide with few branch points Death from hea or liver failure before age 5 Reference: Harper; 30th edition; Table: 18-2; Page no: 179


Question: Muscle cannot make use of glycogen for energy because of deficiency of

Muscle doesn&;t contain glucose -6-phosphate. only liver contain. Glucose -6-phosphatase hydrolyze glycose-6-phosphate into glucose and released into the blood.Ref: DM Vasudevan, 7th edition


Question: Methylation of cytosine is associated with

DNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis. Two of DNA's four bases, cytosine and adenine, can bemethylated Ref satyanarayana 4e


Question: Neurotoxicity is seen with excess of

Neurotoxicity is seen with excess of Vit B6. Toxicity of pyridoxine: Pyridoxine is the only water-soluble vitamin with significant toxicity. Neurologic symptoms (sensory neuropathy) occur at intakes above 200 mg/day, an amount more than 100 times the RDA. Substantial improvement, but not complete recovery, occurs when the vitamin is discontinued. Reference: Lippincott Textbook of Biochemistry pg no. 378


Question: Blue daper syndrome is associated with


Question: Reducing equivalents in fatty acid synthesis are supplied by

Ans. b (NADPH + H+) (Ref. Harper's, Illustrated, 27th/ 87-88, 176)DEHYDROGENASES# Dehydrogenases cause the transfer of hydrogen from one substrate to another in a coupled oxidation-reduction reaction.# These dehydrogenases are specific for their substrates but often utilize common coenzymes or hydrogen carriers, eg, NAD+.# This type of reaction, which enables one substrate to be oxidized at the expense of another, is particularly useful in enabling oxidative processes to occur in the absence of oxygen, such as during the anaerobic phase of glycolysis.# NADH dehydrogenase acts as a carrier of electrons between NADH and the components of higher redox potential. Other dehydrogenases such as succinate dehydrogenase, acyl-CoA dehydrogenase, and mitochondrial glyceroI-3- phosphate dehydrogenase transfer reducing equivalents directly from the substrate to the respiratory chain.# Both NADH and NADPH donate reducing equivalents for the reduction of these cytochromes.# Most of the energy liberated during the oxidation of carbohydrate, fatty acids, and amino acids is made available within mitochondria as reducing equivalents (?H or electrons).# The reduced NADH of the respiratory chain is in turn oxidized by a metalloflavoprotein enzyme--NADH dehydrogenase. This enzyme contains FeS and FMN, is tightly bound to the respiratory chain, and passes reducing equivalents on to Q.# The pentose phosphate pathway, an alternative to part of the pathway of glycolysis, is a source of reducing equivalents (NADPH) for biosynthesis and the source of ribose for nucleotide and nucleic acid synthesis.# The reducing equivalents from the NADH + H+ formed in glycolysis are taken up into mitochondria for oxidation via one of the two shuttles.# NADPH is involved as donor of reducing equivalents in both the reduction of the 3-ketoacyl and of the 2,3-unsaturated acyl derivatives.Also remember:MAJOR OXIDATIVE PATHWAYS WHICH GENERATE ATP AND NADH ARE:# Glycolysis# Fatty acid oxidation# Citric acid cycle and# Electron transport coupled to oxidative phosphorylation (respiratory or electron transport chain)


Question: Acetyl CoA carboxylase is rate limiting enzyme of


Question: A person on total parenteral nutrition was given 62.5 g of protein. Calculate the amount of nitrogen present in this amount of protein.

Approximately, Nitrogen contributes to 16% of proteins 100 gm of protein contains 16 gm of nitrogen. So, 62.5 gm of protein will contain, 62.5 X 16/100 gm of nitrogen, i.e. 10 gm of nitrogen. Extra Edge: Formula for calculating the nitrogen balance of patients: Nitrogen balance = Nitrogen intake - Nitrogen loss = (Protein intake x 0.16) - (24-hour urinary urea nitrogen + 4) Why to add 4? 4 gm of nitrogen is lost through other sources.


Question: DNA repair proofreading in prokaryotes are caused by

The in vivo functionality of Pol II is under debate, yet consensus shows that Pol II is primarily involved as a backup enzyme in prokaryotic DNA replication.The enzyme has 5' - 3' DNA synthesis capability as well as 3' - 5' exonuclease proofreading activity.DNA Pol II interacts with multiple binding paners common with DNA Pol III in order to enhance its fidelity


Question: HDL is increased by

Exercise

Aerobic exercise increases the level of HDL cholesterol.


Question: Enzymes not used in glycogen metabolisma) Glycogen phosphorylase Bb) Glycogen synthase Ic) Glycogen synthase Cd) Glycogen synthase A

Glycogen synthase 1 & Glycogen synthase C


Question: Sickling in &;HbS&; disease is primarily caused by

sickle-cell disease, which is caused by mutation of a single base out of the 3 x 109 in the genome, a T-to-A DNA substitution, which in turn results in an A-to-U change in the mRNA corresponding to the sixth codon of the b-globin gene. The altered codon specifies a different amino acid (valine rather than glutamic acid), and this causes a structural abnormality of the b-globin molecule leading to haemoglobin aggregation and red blood cell "sickling.".When HbS is deoxygenated, it undergoes a pronounced decrease in solubility


Question: Thiamine deficiency causes decreased energy production because rpt Q18

Thiamine pyrophosphate is the biologically active form of the vitamin, formed by the transfer of a pyrophosphate group from adenosine triphosphate (ATP) to thiamine. Thiamine pyrophosphate serves as a coenzyme in the formation or degradation of a-ketols by transketolase.and in the oxidative decarboxylation of a-keto acids. Clinical indications for thiamine The oxidative decarboxylation of pyruvate and a-ketoglutarate, which plays a key role in energy metabolism of most cells, is paicularly impoant in tissues of the nervous system. In thiamine deficiency, the activity of these two dehydrogenase-catalyzed reactions is decreased, resulting in a decreased production of ATP and, thus, impaired cellular function. [Note: Thiamine deficiency is diagnosed by an increase in erythrocyte transketolase activity observed on addition of thiamine pyrophosphate. Ref: Lippincott, 5th edition, page no: 378, 379

It is required for the process of transamination

It is co-enzyme for transketolase in pentose phosphate pathway

It is co-enzyme for pyruvate dehydrogenase


Question: Choose the major fuel that is being adapted by the brain after 1 week of fasting.

The brain then takes up and oxidizes the ketone bodies to derive energy. Consequently, the brain decreases its use of glucose, although glucose is still a major fuel for the brain.Ketone bodies are used by the brain after 3 to 5 days of fasting. This is done to spare protein degradation to provide carbons for gluconeogenesis. Approximately 60% of the brain's energy needs will still be dependent on glucose, but the other 40% can be realized from ketone body oxidation. The brain will not oxidize fatty acids because they have trouble crossing the blood-brain barrier, and the brain has very low levels of glycogen.


Question: Protein implicated in Familial Amyloidosis is

A Classification of AmyloidosisTypeProtein ImplicatedPrimaryPrincipally light chains of immunoglobulinsSecondarySerum amyloid A (SAA)FamilialTransthyretin; also rarely apolipoprotein A-1,cystatin C, fibrinogen, gelsolin, lysozymeAlzheimer's diseaseAmyloid b peptideDialysis-relatedb2-microglobulinRef: Harper&;s Biochemistry; 30th edition; Chapter 52; Plasma Proteins & Immunoglobulins; Table 52-7


Question: The molecular weight of a protein can be determined by

the molecular weight of an unknown protein can be determined by using the SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) method. Although there are some other methods (i.e. analytical ultracentrifugation and light scattering) for calculating the size or molecular weight (MW) of an unknown protein, they are not commonly used for this purpose since they use large amounts of highly purified proteins and require costly equipment.

Native acrylamide Gel Electrophoresis (PAGE)


Question: Okazaki fragments are found during

DNA synthesis is always into 5&; to 3&; direction in both strands The strand which is discontinuously synthesized is referred to as the &;lagging strand &; otherwise called the retrograde strand The small DNA molecules attached to its own primer RNA are called Okazaki fragments The synthesis along the lagging strand is in 5&; to 3&; directionRef: DM Vasudevan, 7th edition, page no: 580, 581


Question: New DNA synthesis occurs in

During this phase, the cell copies its DNA in preparation for mitosis.There are three stages of interphaseG1 (Gap 1), in which the cell grows and functions normally. During this time, a high amount of protein synthesis occurs and the cell growsSynthesis (S), in which the cell duplicates its DNA ( semi-conservative replication).G2 (Gap 2), in which the cell resumes its growth in preparation for division.Ref: DM Vasudevan, 7th edition, page no: 582


Question: Protein synthesis


Question: A molecule used to direct the presence of specific fragment of DNA or RNA is known as

Probe is a fragment of DNA or RNA of variable length (usually 100-1000 bases long) which can be radioactively labeled.It can then be used in DNA or RNA samples to detect the presence of nucleotide sequences (the DNA target) that are complementary to the sequence in the probe.The probe thereby hybridizes to single-stranded nucleic acid (DNA or RNA) whose base sequence allows probe-target base pairing due to complementarity between the probe and target.


Question: The main enzyme responsible for activation of xenobiotics is

Cytochrome P450 (CYP) enzymes in extrahepatic tissues often play a dominant role in target tissue metabolic activation of xenobiotic compounds. They may also determine drug efficacy and influence the tissue burden of foreign chemicals or bioavailability of therapeutic agents.


Question: Pyridoxine is involved in

Pyridoxine is involved in trans-sulfuration.Sulfur-Containing Amino Acids PLP plays an impoant role in methionine and cysteine metabolism. a.Homocysteine + Serine - Cystathionine. (Enzyme Cystathionine synthase) b.Cystathionine - Homoserine + Cysteine (Enzyme Cystathionase) Both these reactions require PLP. Here transfer of sulphur group occurs.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 396


Question: Epimer combination(s) is/are


Question: In sickle cell anaemia, sickle shapes occur due to polymerization of

The substitution of hydrophilic glutamic acid by hydrophobic valine causes a localized stickiness on the surface of the molecule. The deoxygenated HbS may be depicted with a protrusion on one side and a cavity on the other side, so that many molecules can adhere and polymerize.Ref: D M Vasudevan 7th edition Page no: 291,292


Question: Man can not synthesise ascorbic acid due to deficiency of enzyme

ASCORBIC ACID (VITAMIN C):

The active form of vitamin C is ascorbic acid.
Its main function is as a reducing agent.
Vitamin C is a coenzyme in hydroxylation reactions (for example, hydroxylation of prolyl and lysyl residues in collagen) where its role is to keep the iron (Fe) of hydroxylases in the reduced, ferrous (Fe+2) form.
Thus, vitamin C is required for the maintenance of normal connective tissue as well as for wound healing. Vitamin C also facilitates the absorption of dietary nonheme iron from the intestine by reduction of the ferric form (Fe+3) to Fe+2.
Man and other primates, guinea pigs and bats cannot synthesize ascorbic acid due to the deficiency of a single enzyme namely L-gulonolactone oxidase.

Key Concept:
Man cannot synthesize ascorbic acid due to the deficiency of a single enzyme namely L-gulonolactone oxidase.
Ref : Lippincott’s illustrated reviews for biochemistry , 7th edition.


Question: Nohern blotting is used for analysis of

To demonstrate specific RNA The total RNA is isolated from the cell, electrophoresed and then blotted on membrane Probed with radioactive cDNA There will b RNA-DNA hybridization Used to detect the gene expression in a tissueRef: DM Vasudevan, 7th edition, page no: 634


Question: Defect in phenylketonuria

In this condition phenylalanine can&;t be conveed to tyrosine, so phenylalanine accumulates and it&;s level in blood is elevated.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 236, fig 18.1


Question: Gaucher&;s disease is caused by deficiency of


Question: Force not acting in an enzyme substrate complex

This question is a controversial one.
The substrate bind to the active site of the enzyme by noncovalent interactions like hydrogen bond, ionic (electrostatic) bond and hydrophobic bonds.
There is confusion between noncovalent van der Waals forces and covalent bond. Some guides have given option `c' as the answer, which is incorrect.

"Enzymes bind to the substrate by a combination of hydrogen and ionic (electrostatic) bonds, as well as by hydrophobic and van der Waals interactions".
"Most enzyme-substrate combinations are mostly due to noncovalent hydrogen, hydrophobic, ionic (electrostatic) and Van der Waals forces".
"There is a precise substrate interaction that occurs at the active site of enzyme stabilized by numerous weak interactions (hydrogen bonds, electrostatic interactions, hydrophobic contacts, and Van der Walls forces)".

Many other references have mentioned the same.

Thus Van der Walls forces are also involved in enzyme substrate reaction.
Now we are left with covalent bonds. Covalent bonds are also involved in some enzymatic reactions called covalent catalysis. In which there is the formation of covalent bond between enzyme and substrate. The modified enzyme then becomes a reactant. For example, the serine residue at the active site of chymotrypsin forms a covalent link with the substrate.
So, all the four forces given in the options are involved in the enzyme-substrate interaction. However, amongst the given options, I will go for covalent bonds because most of the enzyme-substrate interactions involve weak non-covalent interactions, whereas covalent catalysis mechanism is found only in few enzymes like proteases (chymotrypsin and trypsin) and few others.

The best option, in a given scenario, the answer is a covalent bond.


Question: Base Stacking of DNA is characterised by


Question: Transversion seen in

SubstitutionReplacement of a purine by another purine (A to G or G to A) or pyrimidine by pyrimidine(T to C or C to T) is called transition mutation. If purine is changed to a pyrimidine (A to C) or a pyrimidine to a purine(T to G), it is called a transversion mutation.Ref: Textbook of biochemistry ( DM Vasudevan), 6th edition, page no. 612


Question: Pepsin is a type of

(D) Hydrolase# PEPSIN:> Pepsin is produced by the serous cells of the stomach as pepsinogen, the inactive zymogen or proenzyme.> Pepsin A is the most predominant gastric protease which preferentially cleaves peptide bonds formed by amino groups of phenylalanine or tyrosine or leucine.> Protease or Peptidase or Proteinase: is any enzyme that performs proteolysis; protein catabolism by hydrolysis of peptide bonds.> It break down the bonds by a process - hydrolysis and convert proteins into smaller chains - peptides or even smaller units - amino acids.> Pepsinogen is converted to active pepsin either by autocatalysis, brought about by other pepsin molecules or by gastric HCI (pH < 2).HYDROLASESPhospholipids-PhospholipaseLysophospholipidsLecithin - LysolecithinEnzymes Acting on Peptide Bonds:Exopeptidases-CarboxypeptidaseAiminoacidsEndopeptidase-Aminopeptidases(smallerpeptides)E.g.Pepsin > Removal of a fragment of polypeptide chain (44 amino acids in case of pig enzyme) makes the inactive enzyme active after attaining a proper conformation.> Pepsin is an acid-stable endopeptidase optimally active at a very low pH (2.0).> The active site of the enzyme contains two carboxyl groups, which are maintained at low pH.> Pepsin digestion of proteins results in peptides and a few amino acids which act as stimulants for the release of the hormone cholecystokinin from the duodenum.


Question: Guanido acetic acid is formed in.... from....

Ans. A. Kidney; Arginine + GlycineSteps of synthesis of CreatinineStep I Glycine Arginine Amido TransferaseFirst step in the Kidney.Guanidino group of Arginine is transferred to Glycine to form Guanidino Acetic Acid.Step II Guanidino Acetate Methyl TransferaseSecond step in the LiverCreatine is formedS Adenosyl Methionine is the methyl donorStep III Creatine KinaseThird step in the MuscleCreatine Phosphate is formedStep IVOccur spontaneouslyCreatinine is formed.


Question: Reducing agent used in lipogenesis is derived from

NADPH is involved as donor of reducing equivalents in both the reduction of the 3-ketoacyl and of the 2, 3-unsaturated acyl derivatives. The oxidative reactions of the pentose phosphate are the chief source of the hydrogen required for the reductive synthesis of fatty acids.


Question: Fatty liver is due to excessive accumulation of

Imbalance in the rate of Triacylglycerol Formation & Expo Causes Fatty Liver For a variety of reasons, lipid--mainly as triacylglycerol--can accumulate in the liver. Extensive accumulation is regarded as a pathologic condition. Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder worldwide. When the accumulation of lipid in the liver becomes chronic, inflammatory and fibrotic changes may develop leading to nonalcoholic steatohepatitis (NASH), which can progress to liver diseases including cirrhosis, hepatocarcinoma, and liver failure. Reference: Harper; 30th edition; Page no: 260


Question: Nitric Oxide Synthase

Nitric oxide is formed from arginine by the enzyme nitric-oxide synthase (NOS).It contains heme, FAD, FMN and tetrahydrobiopterin. The enzyme utilizes NADPH and molecular oxygen. Calmodulin is required to modulate its activity.The guanidino nitrogen of arginine is incorporated into NO.. From the molecular oxygen, one atom is added to NO. and the other into citrulline. Therefore, the enzyme is a di-oxygenase Ref: D M Vasudevan 7th edition Page no: 228


Question: Normal serum alkaline phosphatase level is


Question: Fredrickson&;s type II hyperlipoproteinemia is due to excess amount of

Type II: Familial Hypercholesterolaemia (FHC): A common disorder which has been extensively investigated.The disease is characterised by:Hyper b-lipoproteinaemia (LDL |)Associated with increased total cholesterol |VLDL may be raised, hence total TG may be high.But plasma usually remains clear.Inheritance: Autosomal dominant; Frequency--0.2 percentEnzyme deficiency (metabolic defect): There is no enzyme deficiency. Metabolic defects are:An increased synthesis of apo-B |Defective catabolism of LDL. Deficiency of LDL receptors in fibroblasts demonstrated.Clinical features: Xanthomas of tendinous and tuberous type have been describedCorneal arcusOccasionally xanthelasma. Clinically most impoantis the increased incidence of atherosclerosis andpremature cardiovascular diseases.Note: Type-II Pattern can develop as a result of hypothyroidism(secondary hyper or lipoproteinemia).Ref: M.N. Chatterjee - Textbook of Biochemistry, 8th edition, page no: 451


Question: NADPH+, H+ is generated in the reaction catalysed by

Step 1 of HMP Pathway Glucose-6-phosphate is oxidized by NADP+ dependent Glucose-6-phosphate dehydrogenase (GPD). 6-phospho gluconolactone is formed. One molecule of NADPH is formed in the reaction (Fig. 10.1). This is the rate-limiting step. Regulation is affected by this enzyme.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition, Page no: 113


Question: Boiled cabbage or rancid butter smelling urine is seen in

Tyrosinemia REF: Sapira's a & science of bedside diagnosis - Page 138, Textbook of Pediatric Emergency Medicine by Gary R. Fleisher, Stephen Ludwig Page 1566 Tyrosinaemia is an error of metabolism, inherited, in which the body cannot effectively break down the amino acid tyrosine, found in most animal and plant proteins. It is an autosomal recessive, which means two copies of an abnormal gene must be present in order for this to develop. There are three types of tyrosinemia, each with distinctive symptoms and caused by the deficiency of a different enzyme. One of the symptoms of Tyrodinaemia type 1 is an odor like cabbage or rancid butter.


Question: Vitamin C is present in largest amount in body in

Reference: Harpers illustrated biochemistry 30th edition


Question: Rossman flod associated NADH domain is found in

Rossmann fold is seen in family of oxidoreductases that shares a common N-terminal NAD(P)+-D binding domain Lactate dehydrogenase Alcohol dehydrogenase Glyceraldehyde -3-phosphate dehydrogenase Malate dehydrogenase D-glycerate dehydrogenase 6-phosphogluconate dehydrogenase Formate dehydrogenase Reference: Harpers illustrated Biochemistry 31st edition pg 37