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DNB Biochemistry Previous Year Questions

These are the DNB Biochemistry theory questions asked by NBEMS in the December 2025 and June 2025 exams, listed paper by paper as they appeared. The Prep DNB app has all 18 DNB sessions from December 2014 to December 2025 — 720 questions in total — with repeat-question tracking, examiner keywords and MCQs.

Jump to: December 2025 · June 2025 · Important topics · Older papers

DNB Biochemistry December 2025 Question Paper

Paper 1

  1. Define proteinuria. Explain the pathogenesis, biochemical findings and management protocol in different types of proteinuria. [2+8]
  2. Explain proficiency testing (PT) in quality improvement in a clinical biochemistry laboratory. Add a note on delta checks. [6+4]
  3. Enumerate the various mechanisms of enzyme regulation in the body. Explain in detail the underlying mechanism and kinetics of any one of them with suitable examples. [3+7]
  4. Compare and contrast: a) Case control and cohort study. [5] b) Random error and systematic error. [5]
  5. Explain in detail the process of protein isolation and characterization from crude extract. [10]
  6. Explain the clinical significance of estimation of: a) Carbohydrate deficient transferrin. [2.5] b) Fructosamine. [2.5] c) Serum bile acids. [2.5] d) Antimullerian hormone. [2.5]
  7. Explain the process of establishment of reference interval of any analyte. [10]
  8. a) ANOVA. [2.5] b) Random sampling. [2.5] c) PICOT in research. [2.5] d) Type 1 error. [2.5]
  9. Derive the Michaelis-Menten equation and explain its utility in defining enzyme kinetics. [4+6]
  10. Highlight the impact of improper specimen collection on test accuracy and patient outcomes. [10]

Paper 2

  1. Explain the reciprocal regulation of glycolysis and gluconeogenesis. Add a note on the significance of 2,3 - BPG in the body. [6+4]
  2. Explain the short term as well as long term regulation of cholesterol metabolism. Add a note on hypocholesterolemic drugs. [7+3]
  3. Compare and contrast between: a) Glucokinase and hexokinase. [5] b) Transamination and oxidative deamination. [5]
  4. a) Explain the process by which ammonia is handled by brain. [2] b) Explain the process by which specialized products are generated from tryptophan. [4] c) Explain the biochemical defect and clinical manifestation of homocystinuria. [4]
  5. Elaborate the signal transduction mechanism of insulin, highlighting the pathways activated for the different biological functions of insulin. [10]
  6. Explain the process of ATP generation in the mitochondria. Add a note on uncouplers. [7+3]
  7. a) Glycaemic index. [2.5] b) Vegetarian (Vegan) diet and its consequences. [2.5] c) Dietary fibres. [2.5] d) Trans fatty acids and their effects. [2.5]
  8. Explain methemoglobinemia under the headings of: a) Definition. [2] b) Biochemical defect. [4] c) Clinical manifestations. [2] d) Management protocol. [2]
  9. Describe Vitamin A under the headings of: a) Vitamers. [2] b) Biological roles of each vitamer. [4] c) Deficiency manifestations and its management. [4]
  10. Explain the various metabolic alterations that occurs during prolonged fasting. Enumerate the energy sources for brain and RBCs during the various phases of starvation. [8+2]

Paper 3

  1. Explain different models of homologous and nonhomologous recombination. Add a note on pseudogenes. [8+2]
  2. Explain Acquired Immunodeficiency Syndrome (AIDS) under the headings of: a) Pathogenesis. [2] b) Immunological alterations. [2] c) Diagnostic criteria. [3] d) Management protocols. [3]
  3. a) Antibody dependent cell mediated cytotoxicity (ADCC)'. [3] b) Mitochondrial DNA. [4] c) Coordinated regulation of purine and pyrimidine synthesis. [3]
  4. Explain the process of generation of monoclonal antibodies. Add a note on their applications in medicine. [6+4]
  5. Define epigenetics. Discuss the various mechanisms involved in epigenetic modifications and their role in regulation of gene expression. [2+8]
  6. Compare and contrast between: a) TH1 & TH2 cells. [5] b) Genomic and cDNA library. [5]
  7. Explain the process of central and peripheral immune tolerance. [10]
  8. Explain the principles of: a) DNA fingerprinting. [4] b) Chromosome walking. [3] c) Personalized medicine. [3]
  9. Explain the mechanism of exogenous antigen processing by dendritic cells. Add a note on non-professional antigen presenting cells. [7+3]
  10. Enumerate the biochemical changes that occur during the malignant transformation of a cell. Add a note on the role of tumour markers in diagnostics. [5+5]

Paper 4

  1. Explain the principle and use of: a) Liquid Biopsy. [3] b) Digital PCR. [3] c) Electrochemiluminescence. [4]
  2. Differentiate between: a) Turbidimetry and nephelometry. [5] b) Direct and indirect ion selective electrodes. [5]
  3. Explain the principle, instrumentation, uses and precautions while using a single beam spectrophotometer. [10]
  4. Explain the clinical significance of: a) CSF oligoclonal bands. [2.5] b) HER2 neu copy number in breast tumour. [2.5] c) Urinary microalbumin. [2.5] d) Immunoglobulin light chain assay. [2.5]
  5. Explain the role of biochemistry lab in the diagnosis of myocardial infarction. [10]
  6. a) Isoelectric focusing. [5] b) Western blotting. [5]
  7. Explain the principle and interpretation of triple and quadruple test during the antenatal period. [10]
  8. Define point of care testing (POCT). Explain the principle, instrumentation and application of any such device. Add a note on the advantages and disadvantages of POCT over conventional methods. [2+5+3]
  9. Classify stem cells. Explain the different harvesting techniques, applications and potential ethical issues. [10]
  10. Explain in detail the biochemical approach to a patient of precocious puberty. [10]

DNB Biochemistry June 2025 Question Paper

Paper 1

  1. Discuss how internal and external quality control is done in clinical biochemistry laboratory. [10]
  2. a) Michaelis constant in enzyme kinetics. [2] b) Mechanism based enzyme inhibition. [3] c) Allosteric regulation of enzyme activity. [2] d) Therapeutic enzymes. [3]
  3. According to ICMR guidelines for biomedical and health research in human participants, discuss the following: a) Principles of ethical conduct of research. [4] b) Informed consent. [3] c) Recruitment of study population. [3]
  4. a) List different grades of water used in clinical biochemistry lab. How are the different grades of water prepared in laboratory? Mention two uses of each grades of water in Biochemistry lab. [1+2+1] b) Classify centrifuge machines which are used in clinical laboratory based on their: (i) speed. [2] (ii) rotors used. [2] c) Mention the good operating practices to be followed for centrifuge. [2]
  5. a) Role of cell nucleus in accelerate ageing. [2.5] b) Peroxisome biogenesis disorders. [2.5] c) Lysosomal acid lipase deficiency. [2.5] d) Mitochondrial diseases. [2.5]
  6. a) You have been asked to evaluate a new diagnostic test kit in clinical biochemistry lab that involves a new method and is different from that is used conventionally. What parameters will you check for evaluation of the kit? What criteria will you follow before using the kit for patient care? [2+3] b) Discuss the uses of six sigma metrices in clinical laboratory. [5]
  7. Discuss about Arterial Blood Gas (ABG) analysis with respect to: a) Sample collection for ABG analysis. [2.5] b) Parameters measured and calculated by ABG machine. [2.5] c) Principle of blood gas analyser. [2.5] d) ABG parameters altered in metabolic acidosis. [2.5]
  8. Discuss the types of proteinuria, their causes and the types of proteins excreted in each type of proteinuria. [10]
  9. Discuss various methods of blood glucose estimation (including glucometer) under following headings: a) Principle involved in each method. [5] b) Advantages and disadvantages of each method. [5]
  10. a) Linear regression analysis. [2.5] b) Cohort studies. [2.5] c) Meta-analysis. [2.5] d) Impact factor of journal. [2.5]

Paper 2

  1. a) Describe how electron transport chains works, mentioning the role of Q cycle. [6] b) How does extra-mitochondrial NADH enter the mitochondrial matrix? [4]
  2. a) Describe with suitable diagram(s) how different factors affect oxygen dissociation curve of hemoglobin. [6] b) Explain how oxygen dissociation curves for myoglobin and hemoglobin suits their physiological role. [4]
  3. a) Discuss the process of biosynthesis of selenocysteine and its incorporation in proteins. [4] b) List three biomedical importance of selenocysteine. [3] c) How does the biosynthesis and incorporation of hydroxyproline and hydroxylysine in protein differ from those of selenocysteine? [3]
  4. a) Discuss how heme is catabolised to bilirubin. [3] b) Enumerate various causes of unconjugated hyper-bilirubinemia. [3] c) With the help of a table, mention how the liver function test results are used to differentiate between normal population and patients with hyper-bilirubinemia. [4]
  5. a) Discuss the damage caused to DNA, lipids and proteins by free radicals. [6] b) Mention four diseases associated with oxidative stress and write the role of free radicles in pathogenesis of these diseases. [4]
  6. Discuss the principal function(s) and deficiency disease(s) associated with inadequate intake of: a) Vitamin A. [2.5] b) Vitamin K. [2.5] c) Vitamin B1. [2.5] d) Vitamin B2. [2.5]
  7. a) Illustrate the structure of a lipoprotein particle with the help of a labelled diagram. [3] b) List the lipoproteins present in human blood and mention the major lipid(s) carried by them. [4] c) List the apo-lipoproteins and mention their functions. [3]
  8. Describe biochemical defect and management strategies in following inborn errors of metabolism: a) Maple Syrup Urine Disease (MSUD). [2.5] b) HHH syndrome. [2.5] c) Classical galactosemia. [2.5] d) Von Gierke disease. [2.5]
  9. a) Write in detail about one carbon metabolism in human body. [5] b) Discuss the biochemical basis of ammonia toxicity in hepatic failure. How do lactulose and neomycin reduce ammonia level in this condition? [5]
  10. a) Role of pentose phosphate pathway. [2.5] b) Importance of brown adipose tissue. [2.5] c) Insulin signalling pathway. [2.5] d) Glucose transporters. [2.5]

Paper 3

  1. a) Discuss the types of damage to DNA and mechanisms of DNA repair. [6] b) Write about diseases associated with defective DNA repair mechanisms. [4]
  2. Describe the regulation of eukaryotic gene expression by: a) Si (small interfering) RNAs. [5] b) Epigenetic mechanism. [5]
  3. a) How does B-cells produce diverse number of antibodies although their genes producing immunoglobulins are limited? [6] b) Write the molecular mechanism(s) and signal(s) required for class switching of immunoglobulins. [4]
  4. With the help of a labelled diagram, depict the structure of major histocompatibility complex I (MHC-I). Explain the genetic organization of MHC class I and MHC class II molecules and their functions. Define MHC restriction. [3+5+2]
  5. a) List different types of hypersensitivity reactions of immune system and mention in brief the major immunological defect involved in each type of hypersensitivity. [5] b) Explain the immunological basis of positive tuberculin reaction and quantiferon TB gold test. [5]
  6. a) Minimum how many high energy phosphate(s) is/are used to incorporate one amino acid during the process of protein synthesis. Mention the reaction/step which utilizes the high energy phosphates during translation process. [5] b) Write the features of genetic code and define wobbles hypothesis. [5]
  7. a) Mention the function of telomerase. Why is it considered as a potential target for cancer therapy? [5] b) Explain why p53 is called as guardian of the genome. [5]
  8. a) Describe the major differences between the prokaryotic and eukaryotic transcription machineries. [5] b) List the vectors used in recombinant DNA technology for expressing DNA of different size. Write the limitations of using plasmid as a vector. [5]
  9. a) Sources of big data in molecular diagnostics and various databanks. [5] b) Role of genomics and machine learning in personalized medicine. [5]
  10. a) Transgenic animals. [2.5] b) Ubiquitin: Its structure and functions. [2.5] c) RNA editing. [2.5] d) Alternative splicing. [2.5]

Paper 4

  1. Explain the principle and uses of the following techniques in clinical laboratory: a) HPLC. [5] b) qPCR. [5]
  2. a) Explain why a 'primer pair' instead of a 'single primer is used in the polymerase chain reaction (PCR)? [2] b) Name any two computer program used for designing PCR primers. [2] c) What are the properties of an ideal primer set? [3] d) What is difference between reverse transcriptase PCR & real time PCR? Write application(s) of reverse transcriptase PCR and real time PCR. [3]
  3. a) Describe nuclear magnetic resonance (NMR) and its applications in biochemistry. [5] b) Describe MALDI-TOF mass spectrometry and its applications. [5]
  4. a) Whole genome sequencing and genome wide association study. [5] b) Comparative genomic hybridization. [5]
  5. a) What are the sources of cell free DNA (cfDNA) in plasma? [4] b) Discuss applications and potential applications of cfDNA in diagnostics. [6]
  6. Principle and uses of the following techniques: a) SDS-PAGE. [3] b) Density gradient centrifugation. [3] c) Flow cytometry. [4]
  7. Discuss about genome editing technologies, with emphasis on principle of CRISPER-cas9 and its applications. [10]
  8. a) Discuss the various methods to estimate HbA1c. How is the HbA1c test report interpreted? [7] b) How does hemolytic anemia influence HbA1c test result? [3]
  9. Enumerate mutation detection techniques. Discuss any two techniques in detail. [10]
  10. a) Define Artificial Intelligence (AI). Mention its uses in health care. [5] b) How is laboratory diagnosis of CSF-rhinorrhea and chyluria established? [2] c) Write the diagnostic significance of enzyme assay in CSF. [3]

High-Yield DNB Biochemistry Topics

A selection of 29 of the 46 important topics curated in the app from repeated DNB Biochemistry questions.

Clinical biochemistry — highest yield

  • Diabetes mellitus: WHO diagnostic criteria, HbA1c, DKA vs HHS, metabolic complications
  • Acid-base balance: anion gap, metabolic/respiratory disorders, compensation, ABG interpretation
  • Liver function tests: hepatocellular vs cholestatic pattern, De Ritis ratio, jaundice workup

Carbohydrate metabolism

  • Glycolysis and gluconeogenesis: key enzymes, regulation, energetics, Cori and alanine cycles
  • Glycogen metabolism and glycogen storage diseases (types, enzyme defects, clinical features)
  • HMP shunt (pentose phosphate pathway): NADPH, G6PD deficiency and hemolysis

Lipid metabolism

  • Lipoproteins: chylomicrons, VLDL, LDL, HDL metabolism, reverse cholesterol transport
  • Fatty acid beta-oxidation: energetics, carnitine deficiency, ketone body synthesis and ketoacidosis
  • Hyperlipidaemia, PCSK9 inhibitors, and cardiovascular risk

Protein and amino acid metabolism

  • Urea cycle: steps, hyperammonemia, ornithine transcarbamylase deficiency
  • Amino acid disorders: PKU, MSUD, homocystinuria, alkaptonuria — screening and management
  • Purine metabolism: gout, Lesch-Nyhan syndrome, ADA deficiency

Enzymes — always examined

  • Enzyme kinetics: Michaelis-Menten, Lineweaver-Burk, Km and Vmax significance
  • Enzyme inhibition: competitive, non-competitive, uncompetitive, suicide inhibition
  • Isoenzymes: CK-MB, LDH, ALP, cardiac troponins — clinical significance

Vitamins and minerals

  • Fat-soluble vitamins: A (night blindness), D (activation, rickets), E, K (gamma-carboxylation)
  • Water-soluble vitamins: B1 (beriberi), B3 (pellagra), B6 (INH interaction), B12 (folate trap), folate
  • Calcium homeostasis: PTH, vitamin D, calcitonin, osteoporosis markers

Heme, porphyrins, and lysosomal disorders

  • Heme synthesis, porphyrias, and hemoglobinopathies (brief biochemistry link)
  • Lysosomal storage diseases and mucopolysaccharidoses (enzyme defects)
  • Mitochondrial and peroxisomal disorders (Zellweger syndrome)

Energy metabolism

  • TCA cycle: energetics, anaplerotic reactions, regulation
  • Electron transport chain: complexes, inhibitors, uncouplers, chemiosmotic theory

Molecular biology and biotechnology

  • DNA replication, repair (BER, NER, MMR), and diseases (XP, Lynch syndrome)
  • Transcription, RNA processing (splicing, capping), and types of RNA (miRNA, siRNA)
  • Translation, genetic code, and antibiotic inhibitors of protein synthesis

Signal transduction and lab quality

  • Signal transduction: G-proteins (cholera, pertussis), cAMP, JAK-STAT, insulin receptor
  • Laboratory quality control: sensitivity, specificity, precision, accuracy, Westgard rules, Levey-Jennings
  • Pre-analytical errors: sample collection, handling, order of draw

Older DNB Biochemistry Question Papers

The remaining 16 papers are available in the Prep DNB app, organized paper-wise with repeat-question tracking.

Get all 18 papers in the app

Previous Year Questions for Other DNB Subjects