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Important MCQs of Biochemistry on UHS pattern for 2nd year MBBS

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                       Important MCQs of Biochemistry for 2nd yaer MBBS

PDF version is also given at the end of the post.

  1. A 2 year -old boy has been diagnosed with Zellweger syndrome, a disorder caused by malformation of peroxisomes.The oxidation of which of the following fatty acids is impaired in this defect ?
  2. A) Palmitic acid B) Unsaturated fatty acids C) Very long chain fatty acids D) Branched hail fatty acids   E) Cyclic fatty acids
  3. A 63- year-old man with a strong family history of Parkinson’s disease begins to show the signs of the disease “pin rolling tremors”. He visits his neurologist, who guides him about the recent research about coenzyme Q that may stall the development of the disease.

This component of ETC normally

  1. A) receives electrons directly from NADH   B) receives electrons directly from complex IV
  2. C) receives electrons directly from FMN   D) transports ATP to the cytoplasm E) Contains heme
  3. An uncoupler of oxidative Phosphorylation such as dinitrophenol

(A) Inhibits electron transport and ATP synthesis   (B) Allow electron transport to precede without ATP synthesis   (C) Inhibits electron transport without impairment of ATP synthesis

(D) Specially inhibits cytochrome b   (E) Inhibit electron transport and NADP

  1. A new-born infant is found to be having persistent hypoglycemia, despite decreased feeding intervals. The child is also irritable with a moderate degree of hepatomegaly. He is found to have a normal level of muscle fructose 1,6 bisphosphatase but decreased level of liver isoform. Which of the following statement is true of fructose 1,6 bisphosphatase?
  2. A) It is induced by Adenosine mono phosphate (AMP)   B) It is induced by Insulin   C) It is inhibited by Fructose 2,6 bisphosphate   D) It is induced in the fed state     E) It is inhibited during fasting.
  3. A 2-year-old child was brought to pediatric emergency with convulsions. The child was diagnosed with ammonia intoxication due to some urea cycle disorder. Reduced formation of GABA is considered to be the most important cause of convulsion due to depletion of glutamate from where it is produced by decarboxylation. Which of the following intermediates of TCA cycle is involved in the formation of Glutamate ?
  4. A) Succinate   B) Malate   C) α-Keto glutarate   D) Isocitrate   E) Pyruvate.
  5. 30 -year-old man has been diagnosed with familial hypercholesterolemia, a disorder caused by a deficiency of LDL receptors.Which of the following statements best describes the status of these patients ?
  6. A) Serum cholesterol decreases B) Excessive cholesterol is released by HDL C) Cholesterol synthesis by hepatocytes is increased D) Number of LDL receptors on the surface of hepatocytes increaseE) After binding to LDL receptors, LDL is rapidly degrade
  7. A woman was scheduled for a growth hormone suppression test. If each of the following events occurred the morning of the test, which one of the events would be most likely to cause a decrease in growth hormone levels

(A) She ate four large doughnuts for breakfast. (B) She was on estrogen replacement therapy and took her tablets after breakfast. (C) While unlocking her car, she was chased by the neighbor’s vicious dog. (D) She fell asleep at the start of the test and slept soundly until it was completed 1.5 hours later. (E) She forgot to eat her breakfast before the test


  1. Tangier disease is a disease of cholesterol transport. The first case was identified in a patient who lived on the island of Tangier and who had characteristic orange-colored tonsils, a very low HDL and an enlarged liver and spleen. Due to mutation in a transport protein,

cholesterol cannot properly exit the cell to bind to apo A. Which of the following is the most important risk factor for such patients due to deceased level of HDL ?

  1. A) Diabetes mellitus   B) Atherosclerosis   C) Cataract   D) Ketosis   E) Fatty liver
  2. Lack of glucocorticoids and mineralocorticoids might be a consequence of which of the following defects in the adrenal cortex?
  3. A) Estrone deficiency B) Testosterone deficiency C) 17-α hydroxy progesterone deficiency
  4. D) Androstenedione deficiency E) C 21- hydroxylase deficiency
  5. The most important effect of aldosterone is to

(A) Increase the rate of tubular reabsorption of sodium (B) Increase the rate of tubular reabsorption of potassium(C) Decrease the reabsorption of chloride (D) Decrease the renal reabsorption of sodium E) Decrease blood pressure

  1. For Catecholamine biosynthesis the rate limiting enzyme is

A.DOPA decarboxylase (B) Dopamine -hydroxylase (C) Tyrosine hydroxylase

(D) Phenylalanine hydroxylase E) Pheylethanolamine N methyl transferase

  1. Calcitonin causes

(A) Calcinuria and phosphaturia (B) Decrease in urinary calcium (C) Decrease in urinary phosphorous (D) Increase in blood calcium level E) activates osteoblastic activity

  1. Following is a normal overnight fast and a cup of black coffee, a diabetic woman feels slightly nausious and decides to skip breakfast. However she does take her shot of insulin.

This may result in

(A) glycogenolysis (B) Hypoglycemia (C) Increased lipolysis (D) Glycosuria E) glycogenesis

  1. Binding of growth hormone to its receptor results in phosphorylation of

(A) JAK-2 (B) Growth hormone receptor (C) STATs (D) MAPKinase (E) All of these

  1. In inherited deficiency of hypoxanthine guanine phosphoribosyl transferase

(A) De novo synthesis of purine nucleotides is decreased (B) Salvage of purines is decreased

(C) Salvage of purines is increased (D) Synthesis of uric acid is decreased (E) synthesis of uric acid increase

  1. Pancreatic lipase converts triacylglycerol into

(A)2, 3-Diacylglycerol (B)1-Monoacylglycerol (C)2-Monoacylglycerol(D)3-Monoacylglycerol

  1. All of these

17.In small intestine trypsin hydrolyzes peptide linkages containing

(A) Arginine (B) Histidine (C) Serine (D) Aspartate E.Glycine

  1. Chymotrypsin in the small intestine hydrolyzes peptide linkages containing

(A) Alanine (B) Pheynl alanine (C) Valine (D) Methionin E. None of these

19 Arsenic poisoning causes death by affecting the brain. It does this by inhibiting the following enzyme:

A.Dihydrolipoyl transacetylase B.Pyruvate dehydrogenase C.Dihydrolipoyldihydrogenase D.Succinyl dehydrogenase   E.Malate dehydrogenase

20.Which of the following statements concerning the components of the electron transport chain is correct?

  1. All of the components of the electron transport chain are present in large multi-subunit protein complexes embedded in the inner mitochondrial membrane B. Oxygen directly oxidizes cytochromeC C. Succinate Dehydrogenase directly reduces cytochromeC D.The electron transport chain contains some polypeptide chains coded for by the nuclear DNA and some





coded for by the mitochondrial DNA  E. Cyanide inhibits electron flow, but not proton pumping of ATP synthesis

21.Ethanol decreases gluconeogenesis by

  1. Inhibiting glucose-6-phosphatase B. Inhibiting PEP carboxykinase C. Converting NAD+ into NADH and decreasing the availability of pyruvate D.Converting NAD+ into NADH and decreasing the availability of lactate E .Inhibiting glucokinase
  2. The mushroom poison amanitin is an inhibitor of

(A) Protein synthesis (B)mRNA synthesis (C)DNA synthesis (D)Adenosine synthesis

(E) tRNA synthesis

  1. – In patients with Lesch Nyhan Syndrome, purine nucleotides are overproduced and over excreted. The hypoxanthine analogue Allopurinol, which effectively treats gout , has no effect on the severe neurological symptoms of Lesch- Nyhan patients because it does not-
  2. A) Decrease de novo purine synthesis B) Decrease de novo pyrimidine bio synthesis C) Decrease urate synthesis D) Increase PRPP levels(Phosphoribosyl pyrophosphate)E) Inhibit xanthine oxidase

24 The nitrogen atoms for de novo synthesis of purine nucleotides are provided by

(A) Aspartate and glutamate   (B) Aspartate and glycine     (C) Aspartate, glutamine and glycine

(D) Aspartate, glutamate and glycine   (E) lysine and alanine

  1. A 4- year old presents to a pediatric clinic with megaloblastic anemia and failure to thrive. Blood biochemistry reveals “Orotic aciduria”. Enzyme measurement of the white blood cells reveals a deficiency of pyrimidine biosynthesis enzyme Orotate Phospho ribose transferase and abnormally high activity of the enzyme Aspartate transcarbamoylase. Which of the following treatment will reverse all symptoms?
  2. Blood transfusion B) Dietary supplementation of PRPP C) Oral thymidine   D) Oral Uridine
  3. E) Plasmaphresis

26 A 59-year-old woman develops a shuffling gait and a pin- rolling tremor. She is referred to a neurologist for evaluation. After a thorough workup, a diagnosis of Parkinson disease is made and the patient is placed on Mono amine oxidase inhibitor. The drug in this case, is given to decrease the degradation of which of the followings?

  1. A) Serotonin B) Dopamine C) Nicotinamide D) Melatonin E) Nitric oxide
  2. The most likely lethal mutation is

(A) Substitution of adenine for cytosine (B) Insertion of one nucleotide (C) Deletion of three nucleotides (D) Substitution of cytosine for guanine   (E) substitution of lysine for adenine

  1. A 55-year-old man suffers from cirrhosis of liver. Toxins such as ammonia are not properly metabolized by the liver and can damage brain. Which of the following compounds is expected to be in highest concentration in brain as a result of detoxification of ammonia?
  2. A) Alpha keto glutarate B) Glutamate   C)  Glutamine   D) GABA E) Asparagine
  3. RNA primer is formed by the enzyme:

(A) Ribonuclease (B) Primase   (C) DNA polymerase I (D) DNA polymerase III (E) Primer

  1. A particular RNA in a mixture can be identified by

(A) Western blotting (B) Eastern blotting (C) Northern blotting (D) Southern blotting

(E) Electrophoresis

  1. Fragments of DNA can be identified by the technique of

(A)Western blotting(B)Eastern blotting(C)Northern blotting (D)Southern blotting (E)SDS page




32.In a patient with cystic fibrosis, the mutant cystic fibrosis transmembrane conductance regulator (CFTR) protein folds incorrectly.The patient’s cells modify this abnormal protein by attaching ubiquitin molecules to it. What is the fate of this modified CFTR protein?

(A). It performs its normal function, as the ubiquitin largely corrects for the effect of the mutation. (B). It is secreted from the cell.             (C). It is placed into storage vesicles.

(D). It is degraded by the proteasome.     (E). It is repaired by cellular enzymes.

33.A plasmid is a                           

(A) Single stranded linear DNA (B) Single stranded circular DNA(C) Double stranded linear DNA     (D) Double stranded circular DNA         (E) single stranded circular RNA

  1. Rifampicin inhibits

(A) Unwinding of DNA   (B) Initiation of replication   (C) Initiation of translation

(D) Initiation of transcription   (E) Helical DNA

35.Which one of the following is a rate limiting enzyme of gluconeogenesis?

A.Hexokinase B.Phsophofructokinase C.Pyruvate carboxylase D. Pyruvate kinasE.Glucokinase

36.Glycogenin is

A.Uncoupler of oxidative phosphorylation B.Polymer of glycogen molecules C.Protein primer for glycogen synthesis D.Intermediate in glycogen breakdown E.None of them

  1. LCAT is involved in which of the following processes?

A.Converting cholesterol to cholesterol esters B.The transfer of cholesterol esters from HDL to other lipoproteins C.Endocytosis of HDL particles into hepatocytes D .Hydrolysis of HDL

  1. Decreased uptake of cholesterol by hepatocytes
  2. Tetracyline prevents synthesis of polypeptide by

(A) Blocking mRNA formation from DNA   (B) Releasing peptides from mRNA-tRNA complex (C) Competing with mRNA for ribosomal binding sites(D) Preventing binding oaminoacyl tRNA (E) Blocking tRNA from r RN

  1. Phase 1   Biotransformation reaction includes
  2. Dehrogenases B. Hydration C. Hydrolysis D.conjugation E. None of these
  3. During each cycle of β-oxidation

(a) One carbon atom is removed from the carboxyl end of the fatty acid (b) One carbon atom is removed from the methyl end of the fatty acid(c) Two carbon atoms are removed from the carboxyl end of the fatty acid (d) Two carbon atoms are removed from the methyl end of the fatty acid (e) One carbon atom is removed from α carbon

  1. Lysolecithin is formed from lecithin by the action of

(A) Phospholipase A1 (B) Phospholipase A2(C) PhospholipaseC (D)PhospholipaseD

(E) Phospholipase E

  1. From dietary protein as well as from the urea present in fluids secreted into the

gastrointestinal tract intestinal bacteria produce

(A) Carbondioxide (B) Ammonia    (C) Ammonium sulphate   (D) Creatine   (E)Nitrous oxide

  1. The symptom of ammonia intoxication includes

(A) Blurring of vision (B) Constipation (C) Mental confusion (D) Diarrhoea   (E) Skin rashes

  1. Glycerol released from adipose tissue by hydrolysis of triglycerides is mainly

(a) Taken up by liver (b) Taken up by extrahepatic tissues (c) Reutilised in adipose tissue

(d) Excreted from the body   (e) excreted from kidney

45 Transmethylation of guanido acetic acid gives

(A) Creatine phosphate (B) Creatinine(C) Choline(D) n-methyl nicotinamide(E) None of these


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