DNB CET Biochemistry Syllabus

Biochemistry syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Biochemistry in DNB CET, not a summary of it.

1. 1

   Metabolism

   4 topics

   • Carbohydrate Metabolism
     • Glycolysis, gluconeogenesis and regulation
     • TCA cycle and oxidative phosphorylation
     • Glycogen storage diseases
   • Lipid Metabolism
     • Beta-oxidation and ketone body synthesis
     • Cholesterol synthesis and lipoprotein transport
   • Amino acid metabolism and urea cycle
   • Inborn errors of metabolism
2. 2

   Molecular Biology and Genetics

   4 topics

   • DNA replication, repair and mutation
   • Transcription, translation and gene regulation
   • PCR, blotting and recombinant DNA techniques
   • Mendelian and mitochondrial inheritance patterns
3. 3

   Enzymes, Vitamins and Nutrition

   4 topics

   • Enzyme kinetics and inhibition
   • Coenzyme roles of water-soluble vitamins
   • Fat-soluble vitamins and deficiency syndromes
   • Clinical enzymology and tumor markers

Biochemistry flashcards for DNB CET

19 of 59 cards from the Biochemistry deck — real questions with worked answers.

1. What is the rate-limiting enzyme of glycolysis, and what activates vs inhibits it?

   Phosphofructokinase-1 (PFK-1). Activated by AMP and fructose-2,6-bisphosphate; inhibited by ATP and citrate.

2. Which enzyme is the rate-limiting (committed) step of gluconeogenesis, and where does it act?

   Pyruvate carboxylase (mitochondria) converts pyruvate to oxaloacetate; the unique regulatory bypass enzymes also include PEPCK, fructose-1,6-bisphosphatase, and glucose-6-phosphatase.

3. How many net ATP are produced from one glucose via aerobic glycolysis + TCA + oxidative phosphorylation (using ~2.5 ATP/NADH, 1.5/FADH2)?

   Approximately 30-32 net ATP per glucose.

4. What is the net ATP yield of anaerobic glycolysis per glucose?

   2 ATP (net), with regeneration of NAD+ via lactate dehydrogenase converting pyruvate to lactate.

5. Which enzyme deficiency causes Von Gierke disease (GSD type I) and what are the key features?

   Glucose-6-phosphatase deficiency. Features: severe fasting hypoglycemia, hepatomegaly, lactic acidosis, hyperuricemia, hyperlipidemia.

6. Name the glycogen storage diseases and their deficient enzymes for types I, II, III, and V.

   Type I (Von Gierke) – glucose-6-phosphatase; Type II (Pompe) – lysosomal acid alpha-glucosidase (maltase); Type III (Cori) – debranching enzyme; Type V (McArdle) – muscle glycogen phosphorylase.

7. What is the primary purpose and key product of the HMP (pentose phosphate) pathway?

   Produces NADPH (for reductive biosynthesis and glutathione regeneration) and ribose-5-phosphate (for nucleotide synthesis). Rate-limiting enzyme: glucose-6-phosphate dehydrogenase.

8. Why does G6PD deficiency cause hemolysis with oxidant stress?

   Reduced NADPH lowers reduced glutathione, leaving RBCs unable to detoxify oxidative free radicals, causing Heinz bodies and bite cells under stress (drugs, infection, fava beans).

9. What is the committed and rate-limiting step of fatty acid synthesis?

   Acetyl-CoA carboxylase converting acetyl-CoA to malonyl-CoA (requires biotin); activated by citrate and insulin, inhibited by palmitoyl-CoA and glucagon.

10. What shuttle transports long-chain fatty acids into mitochondria for beta-oxidation, and what inhibits it?

    The carnitine shuttle (CPT-I, CPT-II). Malonyl-CoA inhibits CPT-I, preventing fatty acid oxidation during active synthesis.

11. How much ATP is generated from complete beta-oxidation of palmitate (C16)?

    Net 106 ATP (7 cycles producing 7 FADH2 and 7 NADH, plus 8 acetyl-CoA through TCA), minus 2 ATP for activation.

12. Which three ketone bodies are produced, and which is not a true ketone?

    Acetoacetate, beta-hydroxybutyrate (not a true ketone, most abundant), and acetone. HMG-CoA synthase is rate-limiting for ketogenesis in the liver.

13. Which lipoprotein carries the most triglyceride, and which carries the most cholesterol?

    Chylomicrons carry the most dietary triglyceride; LDL carries the most cholesterol. HDL is the densest and most protein-rich (reverse cholesterol transport).

14. What is the rate-limiting enzyme of cholesterol synthesis, and which drug class inhibits it?

    HMG-CoA reductase. Inhibited by statins.

15. Which apolipoprotein is the ligand for the LDL receptor, and which activates lipoprotein lipase?

    ApoB-100 (and ApoE) bind the LDL receptor; ApoC-II activates lipoprotein lipase.

16. What enzyme defect causes classic familial hypercholesterolemia, and the inheritance?

    Defective/absent LDL receptor (autosomal dominant). Causes very high LDL, tendon xanthomas, and premature atherosclerosis.

17. Distinguish glucogenic, ketogenic, and both for amino acid classification.

    Purely ketogenic: Leucine and Lysine. Both glucogenic and ketogenic: Isoleucine, Phenylalanine, Threonine, Tryptophan, Tyrosine. The rest are glucogenic.

18. Where does the urea cycle occur, and which two steps are in the mitochondria?

    Liver; partly mitochondrial, partly cytosolic. Mitochondrial steps: carbamoyl phosphate synthetase I (CPS-I) and ornithine transcarbamoylase (OTC).

19. What is the rate-limiting enzyme of the urea cycle and its essential activator?

    Carbamoyl phosphate synthetase I (CPS-I); requires N-acetylglutamate as an allosteric activator.

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