MCQ 1

Question:
A patient develops severe muscle fatigue during intense exercise. Increased lactate production in skeletal muscle primarily serves to:

Options:
Enhance acetyl-CoA formation
Regenerate cytoplasmic NAD⁺
Increase mitochondrial ATP synthesis
Stimulate gluconeogenesis directly
Activate pyruvate dehydrogenase

Correct Answer:
Regenerate cytoplasmic NAD⁺

Explanation:
During anaerobic glycolysis, lactate dehydrogenase regenerates NAD⁺, allowing glycolysis to continue ATP production.

MCQ 2

Question:
A metabolic pathway in hepatocytes converts lactate released from exercising muscle into glucose. Which process is being described?

Options:
Glycogenesis
Pentose phosphate pathway
Beta oxidation
Cori cycle
Ketogenesis

Correct Answer:
Cori cycle

Explanation:
The Cori cycle transfers lactate from muscle to liver, where it is converted back into glucose.

MCQ 3

Question:
A child with pyruvate dehydrogenase deficiency is expected to have accumulation of:

Options:
Acetyl-CoA
Citrate
Lactate
Succinate
Malate

Correct Answer:
Lactate

Explanation:
Failure of pyruvate conversion into acetyl-CoA diverts pyruvate toward lactate formation.

MCQ 4

Question:
Which tissue depends almost entirely on anaerobic glycolysis for ATP production under normal physiological conditions?

Options:
Cardiac muscle
Hepatocyte
Renal tubular cell
Neuron
Red blood cell

Correct Answer:
Red blood cell

Explanation:
Mature RBCs lack mitochondria and therefore rely completely on glycolysis.

MCQ 5

Question:
A patient with chronic alcoholism develops confusion and lactic acidosis due to impaired pyruvate metabolism. Deficiency of which vitamin is most likely responsible?

Options:
Riboflavin
Niacin
Pantothenic acid
Biotin
Thiamine

Correct Answer:
Thiamine

Explanation:
Thiamine pyrophosphate is a coenzyme of PDH complex; deficiency impairs aerobic glucose metabolism.

MCQ 6

Question:
The irreversible glycolytic reaction converting fructose-6-phosphate into fructose-1,6-bisphosphate is catalyzed by:

Options:
Pyruvate kinase
Hexokinase
Phosphofructokinase-1
Glucose-6-phosphatase
Fructose-1,6-bisphosphatase

Correct Answer:
Phosphofructokinase-1

Explanation:
PFK-1 is the major regulatory and rate-limiting enzyme of glycolysis.

MCQ 7

Question:
A fasting individual maintains blood glucose mainly through hepatic conversion of alanine into glucose. This process primarily occurs in the:

Options:
Lysosome
Golgi apparatus
Smooth endoplasmic reticulum
Mitochondria and cytoplasm
Peroxisome

Correct Answer:
Mitochondria and cytoplasm

Explanation:
Gluconeogenesis involves both mitochondrial and cytoplasmic reactions.

MCQ 8

Question:
Which metabolic change is expected in a patient receiving insulin therapy?

Options:
Reduced GLUT-4 translocation
Enhanced hepatic ketogenesis
Suppressed glycolysis in muscle
Increased glucose uptake into adipose tissue
Activation of hepatic gluconeogenesis

Correct Answer:
Increased glucose uptake into adipose tissue

Explanation:
Insulin stimulates GLUT-4 mediated glucose uptake in adipose tissue and skeletal muscle.

MCQ 9

Question:
Which intermediate acts as a metabolic junction connecting glycolysis, gluconeogenesis, amino acid metabolism, and aerobic respiration?

Options:
Glucose-6-phosphate
Fructose-6-phosphate
Pyruvate
Citrate
Succinyl-CoA

Correct Answer:
Pyruvate

Explanation:
Pyruvate can form lactate, alanine, oxaloacetate, or acetyl-CoA depending on metabolic conditions.

MCQ 10

Question:
A tumor demonstrates increased glucose uptake despite adequate oxygen supply. This metabolic adaptation is best described as:

Options:
Pasteur effect
Warburg effect
Cori effect
Crabtree effect
Randle cycle

Correct Answer:
Warburg effect

Explanation:
Cancer cells preferentially utilize aerobic glycolysis for rapid growth and biosynthesis.

MCQ 11

Question:
Which molecule directly inhibits pyruvate dehydrogenase complex during high-energy states?

Options:
AMP
ADP
Pyruvate
ATP
Calcium ions

Correct Answer:
ATP

Explanation:
ATP indicates sufficient cellular energy and suppresses PDH activity.

MCQ 12

Question:
A deficiency of pyruvate kinase in erythrocytes leads to hemolysis mainly because of impaired:

Options:
DNA synthesis
Protein translation
Membrane ion transport
Hemoglobin formation
Iron absorption

Correct Answer:
Membrane ion transport

Explanation:
Reduced ATP impairs membrane pumps, causing RBC rigidity and hemolysis.

MCQ 13

Question:
Which transporter is primarily responsible for glucose entry into hepatocytes after a carbohydrate-rich meal?

Options:
GLUT-1
GLUT-2
GLUT-3
GLUT-4
SGLT-1

Correct Answer:
GLUT-2

Explanation:
GLUT-2 is present in liver and pancreatic beta cells and facilitates bidirectional glucose transport.

MCQ 14

Question:
The conversion of pyruvate into oxaloacetate during gluconeogenesis requires:

Options:
Biotin
Lipoic acid
NADH
Coenzyme Q
Pyridoxal phosphate

Correct Answer:
Biotin

Explanation:
Pyruvate carboxylase requires biotin as a coenzyme for carboxylation reactions.

MCQ 15

Question:
A patient develops severe hypoglycemia during prolonged fasting due to impaired hepatic glucose release. Which enzyme defect is most likely responsible?

Options:
Hexokinase deficiency
Pyruvate kinase deficiency
Glucose-6-phosphatase deficiency
Phosphoglycerate kinase deficiency
Aldolase deficiency

Correct Answer:
Glucose-6-phosphatase deficiency

Explanation:
Glucose-6-phosphatase converts glucose-6-phosphate into free glucose in gluconeogenesis.

MCQ 16

Question:
Which coenzyme accepts the acetyl group during pyruvate dehydrogenase complex activity?

Options:
FAD
NAD⁺
Coenzyme A
Biotin
TPP

Correct Answer:
Coenzyme A

Explanation:
Coenzyme A accepts the acetyl group to form acetyl-CoA.

MCQ 17

Question:
During vigorous exercise, skeletal muscle relies on anaerobic glycolysis because:

Options:
Fatty acid transport is blocked
Mitochondrial enzymes become inactive
Oxygen delivery becomes insufficient
GLUT-4 transporters are inhibited
Acetyl-CoA formation stops completely

Correct Answer:
Oxygen delivery becomes insufficient

Explanation:
Insufficient oxygen availability shifts metabolism toward anaerobic glycolysis and lactate formation.

MCQ 18

Question:
Which pair of pathways is reciprocally regulated to maintain blood glucose homeostasis?

Options:
Ketogenesis and glycogenesis
Glycolysis and gluconeogenesis
Beta oxidation and lipogenesis
Pentose phosphate pathway and glycogenesis
Urea cycle and glycolysis

Correct Answer:
Glycolysis and gluconeogenesis

Explanation:
These pathways are oppositely regulated to prevent futile cycling and maintain glucose balance.

MCQ 19

Question:
The malate-aspartate shuttle primarily functions to:

Options:
Transfer pyruvate into mitochondria
Generate glucose during fasting
Transport reducing equivalents into mitochondria
Convert lactate into alanine
Regulate glycogen breakdown

Correct Answer:
Transport reducing equivalents into mitochondria

Explanation:
This shuttle transfers cytoplasmic NADH electrons into mitochondria for ATP production.

MCQ 20

Question:
A prolonged fasting state increases hepatic gluconeogenesis mainly to support tissues that are highly dependent on glucose, especially the:

Options:
Cardiac muscle and liver
Adipose tissue and kidney
Brain and red blood cells
Skeletal muscle and skin
Bone and cartilage

Correct Answer:
Brain and red blood cells

Explanation:
Brain and RBCs require continuous glucose supply, especially during fasting conditions.