BIOCHEMISTRY FINAL EXAM (2026–2027)
1. Which biomolecule is the primary source of immediate energy for most cells?
A. Lipids
B. Proteins
C. Carbohydrates
D. Nucleic acids
Answer: C. Carbohydrates
Rationale: Carbohydrates, particularly glucose, are the body's preferred immediate energy source.
Glucose is rapidly metabolized through glycolysis and cellular respiration to generate ATP. Lipids serve
as long-term energy storage, proteins mainly perform structural and functional roles, and nucleic
acids store genetic information.
2. Which enzyme catalyzes the first step of glycolysis?
A. Hexokinase
B. Pyruvate kinase
C. Aldolase
D. Phosphofructokinase-1
Answer: A. Hexokinase
Rationale: Hexokinase phosphorylates glucose to glucose-6-phosphate, trapping glucose inside the
cell. This is the first committed reaction of glycolysis and requires ATP.
3. What is the final product of glycolysis under aerobic conditions?
A. Lactate
B. Acetyl-CoA
C. Pyruvate
D. Citrate
Answer: C. Pyruvate
Rationale: Glycolysis converts one glucose molecule into two pyruvate molecules. Under aerobic
conditions, pyruvate enters the mitochondria for further oxidation. Under anaerobic conditions,
pyruvate is converted to lactate.
4. Which vitamin is a precursor of NAD⁺?
A. Vitamin B1
B. Vitamin B3
C. Vitamin B6
D. Vitamin B12
,Answer: B. Vitamin B3
Rationale: Vitamin B3 (niacin) is the precursor of NAD⁺ and NADP⁺, essential coenzymes in oxidation-
reduction reactions involved in metabolism.
5. The rate-limiting enzyme of glycolysis is:
A. Hexokinase
B. Aldolase
C. Phosphofructokinase-1
D. Enolase
Answer: C. Phosphofructokinase-1
Rationale: PFK-1 catalyzes fructose-6-phosphate to fructose-1,6-bisphosphate and serves as the
major regulatory step of glycolysis. It responds to cellular energy needs through allosteric regulation.
6. ATP stands for:
A. Adenosine Triphosphate
B. Adenine Triphosphate
C. Adenosine Tetraphosphate
D. Adenylate Triphosphate
Answer: A. Adenosine Triphosphate
Rationale: ATP consists of adenine, ribose, and three phosphate groups. It is the primary energy
currency of the cell.
7. The citric acid cycle occurs in the:
A. Cytoplasm
B. Nucleus
C. Mitochondrial matrix
D. Ribosome
Answer: C. Mitochondrial matrix
Rationale: The Krebs cycle takes place in the mitochondrial matrix, where acetyl-CoA is oxidized to
generate NADH, FADH₂, and GTP.
8. Which amino acid contains sulfur?
A. Glycine
B. Valine
C. Methionine
D. Alanine
Answer: C. Methionine
, Rationale: Methionine contains sulfur and is an essential amino acid. Sulfur-containing amino acids
contribute to protein structure and metabolism.
9. Which organ is primarily responsible for detoxification and metabolism?
A. Heart
B. Liver
C. Spleen
D. Pancreas
Answer: B. Liver
Rationale: The liver plays a central role in metabolism, detoxification, glycogen storage, bile
production, and synthesis of plasma proteins.
10. DNA replication is catalyzed by:
A. RNA polymerase
B. DNA ligase
C. DNA polymerase
D. Helicase
Answer: C. DNA polymerase
Rationale: DNA polymerase synthesizes new DNA strands using existing strands as templates during
replication.
11. Which base is found in RNA but not DNA?
A. Adenine
B. Guanine
C. Cytosine
D. Uracil
Answer: D. Uracil
Rationale: RNA contains uracil instead of thymine. Uracil pairs with adenine during RNA synthesis.
12. Which hormone lowers blood glucose levels?
A. Glucagon
B. Cortisol
C. Insulin
D. Epinephrine
Answer: C. Insulin
Rationale: Insulin promotes glucose uptake by cells and stimulates glycogen synthesis, thereby
reducing blood glucose levels.
1. Which biomolecule is the primary source of immediate energy for most cells?
A. Lipids
B. Proteins
C. Carbohydrates
D. Nucleic acids
Answer: C. Carbohydrates
Rationale: Carbohydrates, particularly glucose, are the body's preferred immediate energy source.
Glucose is rapidly metabolized through glycolysis and cellular respiration to generate ATP. Lipids serve
as long-term energy storage, proteins mainly perform structural and functional roles, and nucleic
acids store genetic information.
2. Which enzyme catalyzes the first step of glycolysis?
A. Hexokinase
B. Pyruvate kinase
C. Aldolase
D. Phosphofructokinase-1
Answer: A. Hexokinase
Rationale: Hexokinase phosphorylates glucose to glucose-6-phosphate, trapping glucose inside the
cell. This is the first committed reaction of glycolysis and requires ATP.
3. What is the final product of glycolysis under aerobic conditions?
A. Lactate
B. Acetyl-CoA
C. Pyruvate
D. Citrate
Answer: C. Pyruvate
Rationale: Glycolysis converts one glucose molecule into two pyruvate molecules. Under aerobic
conditions, pyruvate enters the mitochondria for further oxidation. Under anaerobic conditions,
pyruvate is converted to lactate.
4. Which vitamin is a precursor of NAD⁺?
A. Vitamin B1
B. Vitamin B3
C. Vitamin B6
D. Vitamin B12
,Answer: B. Vitamin B3
Rationale: Vitamin B3 (niacin) is the precursor of NAD⁺ and NADP⁺, essential coenzymes in oxidation-
reduction reactions involved in metabolism.
5. The rate-limiting enzyme of glycolysis is:
A. Hexokinase
B. Aldolase
C. Phosphofructokinase-1
D. Enolase
Answer: C. Phosphofructokinase-1
Rationale: PFK-1 catalyzes fructose-6-phosphate to fructose-1,6-bisphosphate and serves as the
major regulatory step of glycolysis. It responds to cellular energy needs through allosteric regulation.
6. ATP stands for:
A. Adenosine Triphosphate
B. Adenine Triphosphate
C. Adenosine Tetraphosphate
D. Adenylate Triphosphate
Answer: A. Adenosine Triphosphate
Rationale: ATP consists of adenine, ribose, and three phosphate groups. It is the primary energy
currency of the cell.
7. The citric acid cycle occurs in the:
A. Cytoplasm
B. Nucleus
C. Mitochondrial matrix
D. Ribosome
Answer: C. Mitochondrial matrix
Rationale: The Krebs cycle takes place in the mitochondrial matrix, where acetyl-CoA is oxidized to
generate NADH, FADH₂, and GTP.
8. Which amino acid contains sulfur?
A. Glycine
B. Valine
C. Methionine
D. Alanine
Answer: C. Methionine
, Rationale: Methionine contains sulfur and is an essential amino acid. Sulfur-containing amino acids
contribute to protein structure and metabolism.
9. Which organ is primarily responsible for detoxification and metabolism?
A. Heart
B. Liver
C. Spleen
D. Pancreas
Answer: B. Liver
Rationale: The liver plays a central role in metabolism, detoxification, glycogen storage, bile
production, and synthesis of plasma proteins.
10. DNA replication is catalyzed by:
A. RNA polymerase
B. DNA ligase
C. DNA polymerase
D. Helicase
Answer: C. DNA polymerase
Rationale: DNA polymerase synthesizes new DNA strands using existing strands as templates during
replication.
11. Which base is found in RNA but not DNA?
A. Adenine
B. Guanine
C. Cytosine
D. Uracil
Answer: D. Uracil
Rationale: RNA contains uracil instead of thymine. Uracil pairs with adenine during RNA synthesis.
12. Which hormone lowers blood glucose levels?
A. Glucagon
B. Cortisol
C. Insulin
D. Epinephrine
Answer: C. Insulin
Rationale: Insulin promotes glucose uptake by cells and stimulates glycogen synthesis, thereby
reducing blood glucose levels.
