📝 Step 5 — KMU Past Papers & Exam Learning

This section contains KMU-style past paper questions designed to strengthen conceptual understanding. Focus on understanding explanations rather than memorizing answers.

🎯 How to Study KMU Past Papers

• Read the question carefully.
• Think about the answer before looking.
• Read the explanation slowly.
• Understand the reasoning behind the correct answer.
• Revise difficult questions again.

MCQ 1

Question:
A child develops acute hemolysis after taking primaquine therapy for malaria. Which intracellular process is most directly impaired in his red blood cells?

Options:
Formation of acetyl-CoA from pyruvate
Maintenance of reduced glutathione
Transport of oxygen by hemoglobin
Synthesis of membrane phospholipids
Generation of ATP by glycolysis

Correct Answer:
Maintenance of reduced glutathione

Explanation:
NADPH generated by the HMP shunt maintains glutathione in reduced form, protecting RBCs from oxidative injury.

MCQ 2

Question:
A rapidly dividing bone marrow cell requires increased ribose-5-phosphate production without excessive NADPH generation. Which portion of the pentose phosphate pathway mainly fulfills this requirement?

Options:
Oxidative phase reactions
Pyruvate oxidation pathway
Non-oxidative sugar interconversion reactions
Mitochondrial electron transport reactions
Anaerobic glycolytic reactions

Correct Answer:
Non-oxidative sugar interconversion reactions

Explanation:
The non-oxidative phase can generate ribose-5-phosphate from glycolytic intermediates without requiring oxidative NADPH production.

MCQ 3

Question:
An RBC exposed to hydrogen peroxide survives because of glutathione-dependent antioxidant defense. Which molecule directly supplies the reducing equivalents for this mechanism?

Options:
NADH
ATP
FADH₂
NADPH
Coenzyme A

Correct Answer:
NADPH

Explanation:
NADPH produced in the oxidative phase regenerates reduced glutathione required for peroxide detoxification.

MCQ 4

Question:
Which tissue would demonstrate the highest activity of the HMP shunt due to active steroid hormone synthesis?

Options:
Cardiac muscle
Adrenal cortex
Skeletal muscle
Articular cartilage
White fibrous tissue

Correct Answer:
Adrenal cortex

Explanation:
Steroid-producing tissues require large amounts of NADPH for cholesterol and steroid biosynthesis.

MCQ 5

Question:
A deficiency of thiamine would most directly impair which enzyme activity in the pentose phosphate pathway?

Options:
Glucose-6-phosphate dehydrogenase
6-phosphogluconate dehydrogenase
Transketolase
Transaldolase
Hexokinase

Correct Answer:
Transketolase

Explanation:
Transketolase requires thiamine pyrophosphate as a coenzyme for carbon transfer reactions.

MCQ 6

Question:
A patient with G6PD deficiency develops jaundice and dark urine after a febrile illness. Which event most likely initiated RBC destruction?

Options:
Reduced ATP production in mitochondria
Failure of globin chain synthesis
Oxidative denaturation of hemoglobin
Defective iron incorporation into heme
Impaired membrane cholesterol synthesis

Correct Answer:
Oxidative denaturation of hemoglobin

Explanation:
Oxidative stress causes hemoglobin precipitation as Heinz bodies, leading to hemolysis.

MCQ 7

Question:
Which feature best distinguishes the pentose phosphate pathway from glycolysis?

Options:
Occurs in cytoplasm
Begins with glucose-6-phosphate
Uses enzyme-catalyzed reactions
Produces reducing equivalents for biosynthesis
Interacts with carbohydrate metabolism

Correct Answer:
Produces reducing equivalents for biosynthesis

Explanation:
PPP primarily generates NADPH for reductive biosynthesis and antioxidant defense, unlike glycolysis which mainly generates ATP.

MCQ 8

Question:
A metabolic pathway converts glucose-6-phosphate into ribulose-5-phosphate with release of carbon dioxide. Which process is represented?

Options:
Citric acid cycle
Beta oxidation pathway
Oxidative phase of PPP
Anaerobic glycolysis
Gluconeogenesis

Correct Answer:
Oxidative phase of PPP

Explanation:
The oxidative phase generates NADPH and ribulose-5-phosphate while releasing CO₂.

MCQ 9

Question:
A neutrophil fails to generate adequate respiratory burst activity during bacterial infection. Deficiency of which metabolite would most directly explain this defect?

Options:
Acetyl-CoA
NADPH
Pyruvate
Oxaloacetate
Lactate

Correct Answer:
NADPH

Explanation:
NADPH is required by NADPH oxidase to generate reactive oxygen species during respiratory burst.

MCQ 10

Question:
An enzyme of the HMP shunt is strongly stimulated when intracellular NADP⁺ concentration rises. Which enzyme shows this regulation?

Options:
Pyruvate kinase
Hexokinase
Glucose-6-phosphate dehydrogenase
Phosphofructokinase-1
Lactate dehydrogenase

Correct Answer:
Glucose-6-phosphate dehydrogenase

Explanation:
G6PD activity increases when NADP⁺ levels rise, signaling increased demand for NADPH.

MCQ 11

Question:
Which metabolic feature explains why RBCs are highly dependent on the pentose phosphate pathway?

Options:
Absence of ribosomes
Absence of glycogen stores
Absence of mitochondria
Absence of membrane proteins
Absence of cytoskeletal filaments

Correct Answer:
Absence of mitochondria

Explanation:
RBCs lack mitochondria and depend entirely on PPP-generated NADPH for antioxidant defense.

MCQ 12

Question:
During the non-oxidative phase of PPP, fructose-6-phosphate and glyceraldehyde-3-phosphate are produced. These intermediates directly connect PPP with:

Options:
Urea cycle
Glycolysis
Beta oxidation
Ketogenesis
Heme synthesis

Correct Answer:
Glycolysis

Explanation:
The non-oxidative phase links PPP to glycolysis through shared intermediates.

MCQ 13

Question:
A patient develops episodic hemolytic anemia after ingestion of fava beans. Which structural abnormality is expected in damaged RBCs?

Options:
Howell-Jolly bodies
Cabot rings
Basophilic stippling
Heinz bodies
Pappenheimer bodies

Correct Answer:
Heinz bodies

Explanation:
Oxidative denaturation of hemoglobin in G6PD deficiency forms Heinz bodies.

MCQ 14

Question:
The primary biochemical purpose of NADPH in fatty tissue is to support:

Options:
ATP generation
Protein catabolism
Fatty acid synthesis
Ketone body oxidation
Glycogen breakdown

Correct Answer:
Fatty acid synthesis

Explanation:
NADPH provides reducing power required for lipogenesis in adipose tissue.

MCQ 15

Question:
A deficiency affecting the oxidative phase of PPP would most immediately reduce cellular ability to:

Options:
Produce pyruvate
Generate ATP
Synthesize glycogen
Neutralize reactive oxygen species
Convert lactate to glucose

Correct Answer:
Neutralize reactive oxygen species

Explanation:
NADPH generated in the oxidative phase is essential for antioxidant protection.

MCQ 16

Question:
Which combination best describes the oxidative phase of the pentose phosphate pathway?

Options:
Reversible reactions with ATP synthesis
Irreversible reactions with NADPH formation
Mitochondrial reactions with oxygen consumption
Anaerobic reactions with lactate production
Cyclic reactions with FADH₂ production

Correct Answer:
Irreversible reactions with NADPH formation

Explanation:
The oxidative phase is irreversible and generates NADPH as its major product.

MCQ 17

Question:
A patient with severe oxidative stress shows impaired regeneration of reduced glutathione. Which reaction directly requires NADPH?

Options:
Reduction of oxidized glutathione
Conversion of pyruvate to lactate
Formation of citrate from oxaloacetate
Oxidation of succinate to fumarate
Phosphorylation of glucose

Correct Answer:
Reduction of oxidized glutathione

Explanation:
Glutathione reductase uses NADPH to regenerate reduced glutathione from oxidized glutathione.

MCQ 18

Question:
Which tissue would have relatively low activity of the pentose phosphate pathway under normal conditions?

Options:
Liver
Lactating mammary gland
Adrenal cortex
Skeletal muscle
Adipose tissue

Correct Answer:
Skeletal muscle

Explanation:
Skeletal muscle has limited need for NADPH-dependent biosynthesis compared to lipogenic tissues.

MCQ 19

Question:
A deficiency of transketolase activity would impair the formation of which type of metabolic products?

Options:
Ketone bodies
Glycolytic intermediates from pentose sugars
Amino acids from pyruvate
Fatty acids from acetyl-CoA
Urea cycle intermediates

Correct Answer:
Glycolytic intermediates from pentose sugars

Explanation:
Transketolase transfers carbon units to generate glycolytic intermediates during the non-oxidative phase.

MCQ 20

Question:
A researcher inhibits glucose-6-phosphate dehydrogenase in cultured cells. Which cellular process would be affected first?

Options:
DNA replication in nucleus
Glycogen breakdown in cytoplasm
Antioxidant defense against peroxide injury
Oxidative phosphorylation in mitochondria
Conversion of pyruvate into lactate

Correct Answer:
Antioxidant defense against peroxide injury

Explanation:
G6PD inhibition decreases NADPH production, rapidly impairing glutathione-dependent antioxidant protection.

📌 Important Exam Strategy

KMU examinations often test integrated understanding rather than isolated facts. Focus on linking anatomy, embryology, histology, and clinical concepts when reviewing questions.

✅ Revision Tip

If you can explain the reason behind the correct answer without looking at notes, your concept is strong.