Practising Biochemistry important questions for NEET PG 2026 is essential because recent exams focus heavily on clinical integration, enzyme defects, metabolic pathways, and genetics.

These questions are designed based on previous year questions (PYQs), recent trends, and high-yield topics.

 

Q1. A child presents with severe fasting hypoglycemia, hepatomegaly, and lactic acidosis. Which enzyme is deficient?

A. Glycogen synthase
B. Glucose-6-phosphatase
C. Hexokinase
D. Pyruvate kinase

Answer: B. Glucose-6-phosphatase

This is Von Gierke disease (Glycogen storage disease type I). Deficiency of glucose-6-phosphatase leads to:

• Severe fasting hypoglycemia
• Lactic acidosis
• Hepatomegaly

 

Q2. A patient has haemolytic anaemia due to decreased ATP production in RBCs. Which enzyme is deficient?

A. Hexokinase
B. Pyruvate kinase
C. Lactate dehydrogenase
D. Glucose-6-phosphate dehydrogenase

Answer: B. Pyruvate kinase

RBCs depend on glycolysis for ATP. Pyruvate kinase deficiency → ↓ ATP → membrane instability → hemolysis.

 

Q3. A child presents with developmental delay and a cherry-red spot on the retina. Which is the most likely diagnosis?

A. Gaucher disease
B. Tay-Sachs disease
C. Niemann-Pick disease
D. Fabry disease

Answer: B. Tay-Sachs disease

Tay-Sachs is due to hexosaminidase A deficiency, leading to GM2 ganglioside accumulation.
Key features:

• Neurodegeneration
• Cherry-red spot
• No hepatosplenomegaly

 

Q4. A patient with obesity has increased levels of which lipoprotein?

A. HDL
B. LDL
C. VLDL
D. Chylomicrons

Answer: C. VLDL

VLDL carries endogenous triglycerides and is elevated in obesity and metabolic syndrome.

 

Q5. A newborn presents with vomiting, lethargy, and a musty odour to the urine. Diagnosis?

A. Alkaptonuria
B. Phenylketonuria
C. Maple syrup urine disease
D. Homocystinuria

Answer: B. Phenylketonuria

Phenylketonuria (PKU) is due to phenylalanine hydroxylase deficiency:

• Musty odor
• Intellectual disability
• Elevated phenylalanine

 

Q6. Maple syrup urine disease is due to a deficiency of:

A. Branched-chain amino acid dehydrogenase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. Homogentisate oxidase

Answer: A

MSUD involves defective metabolism of:

• Leucine
• Isoleucine
• Valine

Leading to sweet-smelling urine and neurological symptoms.

 

Q7. Which enzyme shows zero-order kinetics at high substrate concentration?

A. Allosteric enzyme
B. Michaelis-Menten enzyme
C. Competitive enzyme
D. Non-competitive enzyme

Answer: B. Michaelis-Menten enzyme

At high substrate concentration, enzymes become saturated → reaction rate becomes constant → zero-order kinetics.

 

Q8. A competitive inhibitor affects which parameter?

A. Decreases Vmax
B. Increases Vmax
C. Increases Km
D. Decreases Km

Answer: C. Increases Km

Competitive inhibition:

• Km increases (lower affinity)
• Vmax remains unchanged

 

Q9. Which enzyme is responsible for removing RNA primers during DNA replication?

A. DNA polymerase I
B. DNA polymerase II
C. DNA polymerase III
D. Helicase

Answer: A. DNA polymerase I

DNA polymerase I has exonuclease activity that removes RNA primers and fills gaps.

 

Q10. In which direction does DNA synthesis occur?

A. 3′ → 5′
B. 5′ → 3′
C. Both directions
D. Random

Answer: B. 5′ → 3′

DNA polymerase adds nucleotides only in the 5′ to 3′ direction.

 

Q11. A patient presents with bleeding gums and poor wound healing. Deficiency of:

A. Vitamin A
B. Vitamin C
C. Vitamin D
D. Vitamin K

Answer: B. Vitamin C

Vitamin C is required for collagen synthesis. Deficiency → scurvy:

• Bleeding gums
• Poor healing

 

Q12. Night blindness is due to a deficiency of:

A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K

Answer: A. Vitamin A

Vitamin A is essential for rhodopsin formation in the retina.

 

Q13. A patient with liver disease shows increased ammonia levels. Which pathway is affected?

A. Glycolysis
B. Urea cycle
C. TCA cycle
D. Pentose phosphate pathway

Answer: B. Urea cycle

The liver converts ammonia to urea. Liver failure → hyperammonemia → encephalopathy.

 

Q14. A patient presents with gout. Which metabolite is elevated?

A. Urea
B. Creatinine
C. Uric acid
D. Ammonia

Answer: C. Uric acid

Gout results from uric acid accumulation due to a purine metabolism disorder.

 

Q15. Rate-limiting enzyme of glycolysis:

A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Glucose-6-phosphatase

Answer: B

PFK-1 is the key regulatory enzyme of glycolysis.

 

Q16. NADH is produced in:

A. Glycolysis
B. TCA cycle
C. Beta-oxidation
D. All of the above

Answer: D

NADH is generated in multiple pathways, including glycolysis, the TCA cycle, and fatty acid oxidation.

 

Q17. Which vitamin acts as a coenzyme in transamination reactions?

A. Vitamin B1
B. Vitamin B6
C. Vitamin B12
D. Vitamin C

Answer: B. Vitamin B6

Pyridoxine (B6) is required for transamination reactions.

 

Q18. In oxidative phosphorylation, ATP is generated by:

A. Substrate-level phosphorylation
B. Electron transport chain
C. Glycolysis
D. Fermentation

Answer: B

ATP is produced via oxidative phosphorylation in mitochondria.

 

Q19. A patient with G6PD deficiency develops hemolysis after drug intake. Cause?

A. ATP deficiency
B. Increased oxidative stress
C. Decreased haemoglobin
D. Increased glucose

Answer: BG6PD produces NADPH → protects RBCs from oxidative damage. Deficiency → hemolysis.

 

Q20. Which pathway produces NADPH?

A. Glycolysis
B. TCA cycle
C. Pentose phosphate pathway
D. Urea cycle

Answer: C

PPP generates NADPH for:

• Fatty acid synthesis
• Antioxidant defense

These Biochemistry important questions for NEET PG 2026 reflect:

• Clinical case-based learning
• High-yield enzyme and pathway concepts
• PYQ-focused patterns

To score well:

• Focus on metabolic pathways and their regulation
• Practice clinical MCQs regularly
• Revise enzymes, vitamins, and genetics thoroughly