Q.1 Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate in glycolysis?
Hexokinase
Phosphofructokinase
Aldolase
Pyruvate kinase
Explanation - Hexokinase phosphorylates glucose to form glucose-6-phosphate, the first step of glycolysis.
Correct answer is: Hexokinase
Q.2 Which of the following pathways occurs in the cytoplasm?
Glycolysis
TCA Cycle
Electron Transport Chain
Beta-oxidation
Explanation - Glycolysis takes place in the cytoplasm, while TCA cycle and ETC occur in mitochondria.
Correct answer is: Glycolysis
Q.3 Which molecule is the final product of glycolysis under aerobic conditions?
Ethanol
Lactate
Acetyl-CoA
Pyruvate
Explanation - Glycolysis produces pyruvate, which can enter mitochondria and be converted to acetyl-CoA under aerobic conditions.
Correct answer is: Pyruvate
Q.4 Which enzyme is considered the rate-limiting step of glycolysis?
Hexokinase
Phosphofructokinase-1
Pyruvate kinase
Enolase
Explanation - PFK-1 controls glycolysis by catalyzing the irreversible phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate.
Correct answer is: Phosphofructokinase-1
Q.5 In the absence of oxygen, pyruvate is converted into:
Acetyl-CoA
Lactate
Oxaloacetate
Citrate
Explanation - Anaerobic glycolysis reduces pyruvate to lactate to regenerate NAD+ for glycolysis.
Correct answer is: Lactate
Q.6 The Cori cycle involves transfer of which metabolite between muscle and liver?
Pyruvate
Glucose-6-phosphate
Lactate
Fructose
Explanation - In the Cori cycle, muscles produce lactate which is transported to the liver, converted to glucose, and returned to muscle.
Correct answer is: Lactate
Q.7 Which coenzyme is required for pyruvate dehydrogenase complex?
NAD+
FAD
Thiamine pyrophosphate (TPP)
Biotin
Explanation - The pyruvate dehydrogenase complex requires TPP, NAD+, FAD, CoA, and lipoic acid.
Correct answer is: Thiamine pyrophosphate (TPP)
Q.8 Where does the TCA cycle occur?
Cytoplasm
Mitochondrial matrix
Golgi apparatus
Endoplasmic reticulum
Explanation - The tricarboxylic acid (TCA) cycle occurs in the mitochondrial matrix.
Correct answer is: Mitochondrial matrix
Q.9 Which enzyme catalyzes the conversion of phosphoenolpyruvate to pyruvate?
Enolase
Pyruvate kinase
Aldolase
Lactate dehydrogenase
Explanation - Pyruvate kinase converts phosphoenolpyruvate into pyruvate, yielding ATP.
Correct answer is: Pyruvate kinase
Q.10 How many ATP molecules are produced (net gain) from one glucose molecule in glycolysis?
2
4
6
8
Explanation - Glycolysis consumes 2 ATP but generates 4 ATP, giving a net gain of 2 ATP.
Correct answer is: 2
Q.11 Which enzyme bypasses pyruvate kinase in gluconeogenesis?
PEP carboxykinase
Pyruvate carboxylase
Glucose-6-phosphatase
Fructose-1,6-bisphosphatase
Explanation - PEP carboxykinase converts oxaloacetate to PEP, bypassing the irreversible pyruvate kinase step of glycolysis.
Correct answer is: PEP carboxykinase
Q.12 The primary regulatory enzyme of gluconeogenesis is:
Pyruvate carboxylase
Glucose-6-phosphatase
Fructose-1,6-bisphosphatase
Hexokinase
Explanation - Fructose-1,6-bisphosphatase catalyzes the rate-limiting step of gluconeogenesis.
Correct answer is: Fructose-1,6-bisphosphatase
Q.13 Which hormone stimulates glycogenolysis in the liver?
Insulin
Glucagon
Cortisol
Thyroxine
Explanation - Glucagon activates glycogen phosphorylase via cAMP, leading to glycogen breakdown in the liver.
Correct answer is: Glucagon
Q.14 The branching enzyme in glycogen synthesis creates which type of bond?
α-1,4 linkage
α-1,6 linkage
β-1,4 linkage
β-1,6 linkage
Explanation - Branching enzyme introduces α-1,6 glycosidic bonds to create branches in glycogen.
Correct answer is: α-1,6 linkage
Q.15 The enzyme glucose-6-phosphatase is absent in:
Liver
Kidney
Muscle
Intestine
Explanation - Muscle lacks glucose-6-phosphatase, preventing it from releasing free glucose into the blood.
Correct answer is: Muscle
Q.16 Which of the following is NOT an intermediate of glycolysis?
Fructose-1,6-bisphosphate
Glyceraldehyde-3-phosphate
Citrate
2-Phosphoglycerate
Explanation - Citrate belongs to the TCA cycle, not glycolysis.
Correct answer is: Citrate
Q.17 Which of the following pathways produces NADPH?
Glycolysis
Pentose phosphate pathway
TCA cycle
Gluconeogenesis
Explanation - The pentose phosphate pathway generates NADPH for biosynthesis and antioxidant defense.
Correct answer is: Pentose phosphate pathway
Q.18 Which enzyme deficiency causes McArdle’s disease?
Glycogen synthase
Glycogen phosphorylase (muscle)
Branching enzyme
Debranching enzyme
Explanation - McArdle’s disease is due to muscle glycogen phosphorylase deficiency, leading to exercise intolerance.
Correct answer is: Glycogen phosphorylase (muscle)
Q.19 The committed step of glycolysis is catalyzed by:
Hexokinase
Phosphofructokinase-1
Pyruvate kinase
Phosphoglucose isomerase
Explanation - PFK-1 is considered the committed step of glycolysis, ensuring the glucose is used for energy.
Correct answer is: Phosphofructokinase-1
Q.20 Which enzyme is inhibited by arsenic in carbohydrate metabolism?
Pyruvate dehydrogenase
Hexokinase
Phosphoglycerate mutase
Pyruvate kinase
Explanation - Arsenic inhibits enzymes requiring lipoic acid, such as pyruvate dehydrogenase and α-ketoglutarate dehydrogenase.
Correct answer is: Pyruvate dehydrogenase
Q.21 What is the primary substrate for gluconeogenesis?
Acetyl-CoA
Lactate
Fatty acids
Cholesterol
Explanation - Lactate, glycerol, and glucogenic amino acids are primary substrates for gluconeogenesis, not acetyl-CoA.
Correct answer is: Lactate
Q.22 Which step of glycolysis directly produces NADH?
Hexokinase reaction
Glyceraldehyde-3-phosphate dehydrogenase reaction
Phosphofructokinase reaction
Pyruvate kinase reaction
Explanation - Glyceraldehyde-3-phosphate dehydrogenase oxidizes glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate, producing NADH.
Correct answer is: Glyceraldehyde-3-phosphate dehydrogenase reaction
Q.23 Which enzyme deficiency causes Von Gierke’s disease?
Debranching enzyme
Glucose-6-phosphatase
Glycogen phosphorylase
Branching enzyme
Explanation - Von Gierke’s disease (Type I glycogen storage disease) is caused by deficiency of glucose-6-phosphatase.
Correct answer is: Glucose-6-phosphatase
Q.24 Which of the following is an allosteric inhibitor of phosphofructokinase-1?
Citrate
AMP
Fructose-2,6-bisphosphate
ADP
Explanation - Citrate acts as an allosteric inhibitor of PFK-1, linking glycolysis to the TCA cycle status.
Correct answer is: Citrate