NET/SLET Life Science (Biochemistry)
Table of Contents
Introduction to UGC CSIR NET SLET
Preparing for the UGC CSIR NET Life Sciences Exam requires a strong command over Biochemistry, one of the most crucial sections of the syllabus. To help aspirants practice effectively, we have compiled a set of 50 hard-level Biochemistry MCQs with answers. These questions are designed according to the latest exam pattern and cover important topics such as enzymology, metabolism, bioenergetics, vitamins, amino acid metabolism, and molecular pathways.
By solving these MCQs, candidates can test their knowledge, identify weak areas, and improve problem-solving speed. Since Biochemistry forms the backbone of advanced topics in Cell Biology, Molecular Biology, and Physiology, mastering these questions will significantly boost your chances of scoring high in the exam.
Use this practice set to revise key concepts, build confidence, and get a real-time exam-like experience before appearing for UGC CSIR NET 2025 or other competitive exams like GATE, ICMR-JRF, and DBT-BET.
The following MCQs are prepared only for educational and practice purposes. While we have made every effort to ensure the accuracy of the content, actual exam questions may differ. Candidates are advised to use these questions as a supplementary study resource along with standard textbooks and official reference materials.
đ§Ē Biochemistry â 50 MCQs with Answers (UGC CSIR NET)
Q1. Which amino acid has an imidazole side chain and is commonly found in enzyme active sites due to its ability to donate and accept protons at physiological pH?
A) Lysine
B) Arginine
C) Histidine
D) Proline
Answer: C) Histidine
Q2. In the electron transport chain, which complex does NOT contribute to proton pumping across the inner mitochondrial membrane?
A) Complex I
B) Complex II
C) Complex III
D) Complex IV
Answer: B) Complex II
Q3. The prosthetic group covalently bound to cytochrome c, allowing it to carry electrons, is:
A) FAD
B) FMN
C) Heme c
D) Heme a
Answer: C) Heme c
Q4. Which enzyme catalyzes the first committed and irreversible step of glycolysis, making it the main regulatory point?
A) Hexokinase
B) Phosphoglycerate kinase
C) Pyruvate kinase
D) Phosphofructokinase-1 (PFK-1)
Answer: D) Phosphofructokinase-1
Q5. The vitamin-derived coenzyme required for all transamination reactions is:
A) Biotin
B) Pyridoxal phosphate (Vitamin B6)
C) Thiamine pyrophosphate (Vitamin B1)
D) NADâē (Vitamin B3)
Answer: B) Pyridoxal phosphate (Vitamin B6)
Q6. Which enzyme deficiency leads to LeschâNyhan syndrome, characterized by self-mutilation and uric acid overproduction?
A) Adenosine deaminase
B) HGPRT (Hypoxanthine-guanine phosphoribosyltransferase)
C) PRPP synthetase
D) Xanthine oxidase
Answer: B) HGPRT
Q7. The committed step in cholesterol biosynthesis is catalyzed by:
A) HMG-CoA reductase
B) HMG-CoA synthase
C) Mevalonate kinase
D) Squalene synthase
Answer: A) HMG-CoA reductase
Q8. Which amino acid is considered purely ketogenic, entering metabolism only as acetyl-CoA or acetoacetate?
A) Valine
B) Leucine
C) Isoleucine
D) Threonine
Answer: B) Leucine
Q9. The rate-limiting enzyme of the urea cycle, requiring N-acetylglutamate as an activator, is:
A) Ornithine transcarbamoylase
B) Carbamoyl phosphate synthetase I
C) Argininosuccinate lyase
D) Arginase
Answer: B) Carbamoyl phosphate synthetase I
Q10. Which of the following is the primary storage protein for iron in mammalian cells?
A) Hemoglobin
B) Myoglobin
C) Ferritin
D) Hemosiderin
Answer: C) Ferritin
Q11. The amino acid precursor of serotonin, which is further converted into melatonin, is:
A) Tyrosine
B) Tryptophan
C) Histidine
D) Phenylalanine
Answer: B) Tryptophan
Q12. The vitamin essential for hydroxylation of proline and lysine residues during collagen synthesis is:
A) Vitamin A
B) Vitamin C
C) Vitamin D
D) Vitamin K
Answer: B) Vitamin C
Q13. Which enzyme catalyzes the conversion of superoxide radicals into hydrogen peroxide?
A) Catalase
B) Superoxide dismutase
C) Glutathione peroxidase
D) Peroxidase
Answer: B) Superoxide dismutase
Q14. In the Cori cycle, lactate produced by anaerobic glycolysis in muscle is transported to the liver, where it is converted to:
A) Pyruvate
B) Alanine
C) Glucose
D) Acetyl-CoA
Answer: C) Glucose
Q15. The amino acid precursor of nitric oxide (NO), a vasodilator synthesized by nitric oxide synthase, is:
A) Glycine
B) Serine
C) Arginine
D) Aspartate
Answer: C) Arginine
Q16. Which type of enzyme inhibition results in a parallel Lineweaver-Burk plot and decreases both Km and Vmax?
A) Competitive inhibition
B) Noncompetitive inhibition
C) Mixed inhibition
D) Uncompetitive inhibition
Answer: D) Uncompetitive inhibition
Q17. The abnormal accumulation of homogentisic acid due to homogentisate oxidase deficiency results in which metabolic disorder?
A) Alkaptonuria
B) Phenylketonuria
C) Maple syrup urine disease
D) Tyrosinemia type I
Answer: A) Alkaptonuria
Q18. The Bohr effect in hemoglobin refers to:
A) Increased Oâ affinity with decreased pH
B) Decreased Oâ affinity with decreased pH
C) Increased Oâ affinity with increased COâ
D) No change in Oâ affinity with pH
Answer: B) Decreased Oâ affinity with decreased pH
Q19. Which vitamin is required for the carboxylation reactions of pyruvate carboxylase and acetyl-CoA carboxylase?
A) Biotin
B) Riboflavin
C) Niacin
D) Thiamine
Answer: A) Biotin
Q20. The enzyme deficient in maple syrup urine disease is:
A) Phenylalanine hydroxylase
B) Branched-chain Îą-keto acid dehydrogenase
C) Tyrosinase
D) Glucose-6-phosphate dehydrogenase
Answer: B) Branched-chain Îą-keto acid dehydrogenase
Q21. The Km value of an enzyme indicates:
A) Maximum velocity of enzyme reaction
B) Substrate concentration at half of Vmax
C) Binding affinity of enzyme to product
D) Rate-limiting step of catalysis
Answer: B) Substrate concentration at half of Vmax
Q22. Which amino acid introduces a structural kink in Îą-helices due to its rigid cyclic structure?
A) Glycine
B) Serine
C) Proline
D) Valine
Answer: C) Proline
Q23. The major apolipoprotein of low-density lipoprotein (LDL) is:
A) ApoA-I
B) ApoB-100
C) ApoC-II
D) ApoE
Answer: B) ApoB-100
Q24. The vitamin required as a coenzyme for methylmalonyl-CoA mutase is:
A) Vitamin B2
B) Vitamin B6
C) Vitamin B12
D) Vitamin B7
Answer: C) Vitamin B12
Q25. The substrate-level phosphorylation step in the TCA cycle is catalyzed by:
A) Isocitrate dehydrogenase
B) Succinyl-CoA synthetase
C) Malate dehydrogenase
D) Aconitase
Answer: B) Succinyl-CoA synthetase
Q26. The coenzyme required for oxidative deamination by glutamate dehydrogenase is:
A) NADâē/NADPâē
B) FAD
C) Biotin
D) Coenzyme A
Answer: A) NADâē/NADPâē
Q27. The main intracellular buffering system in human cells is:
A) Carbonic acidâbicarbonate buffer
B) Phosphate buffer
C) Hemoglobin buffer
D) Ammonium buffer
Answer: B) Phosphate buffer
Q28. Which glycolytic enzyme is known to translocate to the nucleus and regulate gene expression in cancer cells?
A) Hexokinase
B) Pyruvate kinase (PKM2)
C) Enolase
D) Aldolase
Answer: B) Pyruvate kinase (PKM2)
Q29. The carnitine shuttle is essential for transporting which molecules into the mitochondrial matrix?
A) Glucose
B) Long-chain fatty acids
C) Ketone bodies
D) Pyruvate
Answer: B) Long-chain fatty acids
Q30. The major product of the RapoportâLuebering shunt in red blood cells is:
A) NADPH
B) 2,3-Bisphosphoglycerate (2,3-BPG)
C) ATP
D) Fumarate
Answer: B) 2,3-Bisphosphoglycerate (2,3-BPG)
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