📝 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 fasting student has increased fatty acid oxidation in the liver. Which metabolic change most directly favors ketone body formation?

Options:
Increased availability of oxaloacetate
Decreased mitochondrial acetyl-CoA
Diversion of oxaloacetate toward gluconeogenesis
Increased conversion of pyruvate to lactate
Increased glycogen synthesis in liver

Correct Answer:
Diversion of oxaloacetate toward gluconeogenesis

Explanation:
During fasting, oxaloacetate is used for gluconeogenesis, limiting TCA cycle activity. Excess acetyl-CoA is therefore diverted toward ketogenesis.

MCQ 2

Question:
A patient with uncontrolled type 1 diabetes develops deep rapid breathing. Which biochemical event best explains this finding?

Options:
Excess glucose storage in liver
Increased ketone body accumulation
Reduced fatty acid entry into liver
Increased phospholipid degradation
Reduced acetone formation

Correct Answer:
Increased ketone body accumulation

Explanation:
Excess ketone bodies lower blood pH, producing metabolic acidosis. Kussmaul breathing occurs as respiratory compensation.

MCQ 3

Question:
The liver produces ketone bodies but does not use them for energy. This is because hepatocytes lack:

Options:
HMG-CoA synthase
Thiophorase
Acetoacetate decarboxylase
Beta-hydroxybutyrate dehydrogenase
Fatty acyl-CoA synthetase

Correct Answer:
Thiophorase

Explanation:
Thiophorase is needed for ketone body utilization in extrahepatic tissues. Its absence in liver prevents hepatic use of ketone bodies.

MCQ 4

Question:
During prolonged starvation, the brain begins to use ketone bodies. The major advantage of this adaptation is:

Options:
Reduced dependence on blood glucose
Increased storage of glycogen
Complete inhibition of fatty acid oxidation
Increased synthesis of cholesterol
Reduced need for oxygen delivery

Correct Answer:
Reduced dependence on blood glucose

Explanation:
Ketone bodies provide an alternative fuel for the brain during prolonged fasting, reducing glucose requirement and protein breakdown.

MCQ 5

Question:
A diabetic patient has fruity breath odor. Which ketone body is mainly responsible?

Options:
Acetoacetate
Beta-hydroxybutyrate
Acetone
Acetyl-CoA
Acetoacetyl-CoA

Correct Answer:
Acetone

Explanation:
Acetone is volatile and is exhaled through lungs, producing fruity breath odor in diabetic ketoacidosis.

MCQ 6

Question:
A child has hepatosplenomegaly and progressive neurodegeneration due to sphingomyelin accumulation. Which enzyme is deficient?

Options:
Ceramidase
Sphingomyelinase
Glucocerebrosidase
Hexosaminidase A
Phospholipase A2

Correct Answer:
Sphingomyelinase

Explanation:
Niemann-Pick disease results from sphingomyelinase deficiency, causing sphingomyelin accumulation in lysosomes.

MCQ 7

Question:
Phosphatidic acid is clinically important because it serves as a common precursor for:

Options:
Ketone bodies and glucose
TAG and glycerophospholipids
Ceramide and sphingosine
Cholesterol and bile salts
Glycogen and lactose

Correct Answer:
TAG and glycerophospholipids

Explanation:
Phosphatidic acid is a central intermediate in complex lipid metabolism, forming triacylglycerols and glycerophospholipids.

MCQ 8

Question:
A defect in glycerophospholipid synthesis would most directly affect:

Options:
Mitochondrial DNA replication
Cell membrane structure
Ketone body utilization
Urea cycle function
Glycogen breakdown

Correct Answer:
Cell membrane structure

Explanation:
Glycerophospholipids are major structural components of biological membranes and are essential for membrane stability.

MCQ 9

Question:
A patient with ceramidase deficiency develops painful joint deformities and neurological problems. The accumulated molecule is:

Options:
Sphingomyelin
Ceramide
Phosphatidic acid
Triacylglycerol
Acetoacetate

Correct Answer:
Ceramide

Explanation:
Farber disease is caused by ceramidase deficiency, leading to ceramide accumulation in tissues.

MCQ 10

Question:
Which pathway best explains the formation of sphingomyelin?

Options:
Glycerol-3-phosphate → phosphatidic acid → sphingomyelin
Acetyl-CoA → HMG-CoA → sphingomyelin
Ceramide → addition of phosphocholine → sphingomyelin
Acetoacetate → acetone → sphingomyelin
Fatty acyl-CoA → malonyl-CoA → sphingomyelin

Correct Answer:
Ceramide → addition of phosphocholine → sphingomyelin

Explanation:
Sphingomyelin is synthesized from ceramide by addition of a phosphocholine group.

MCQ 11

Question:
Which tissue is most dependent on sphingomyelin for normal function?

Options:
Myelinated nerve tissue
Hepatic sinusoidal tissue
Renal collecting duct
Adipose storage tissue
Skeletal cartilage tissue

Correct Answer:
Myelinated nerve tissue

Explanation:
Sphingomyelin is a major lipid of myelin sheath and is essential for normal nerve conduction.

MCQ 12

Question:
In uncontrolled diabetes mellitus, ketogenesis increases mainly because insulin deficiency causes:

Options:
Reduced lipolysis in adipose tissue
Increased fatty acid delivery to liver
Increased glycogen formation in muscle
Reduced acetyl-CoA production
Increased protein storage in liver

Correct Answer:
Increased fatty acid delivery to liver

Explanation:
Insulin deficiency activates lipolysis, increasing free fatty acid delivery to the liver and promoting ketogenesis.

MCQ 13

Question:
A student asks why ketone bodies are useful during fasting. The best explanation is that they are:

Options:
Water-soluble transportable fuel molecules
Major storage molecules in adipose tissue
Structural components of cell membranes
Precursors of steroid hormones
Major products of glycogen breakdown

Correct Answer:
Water-soluble transportable fuel molecules

Explanation:
Ketone bodies are water-soluble and can travel in blood to provide energy to extrahepatic tissues.

MCQ 14

Question:
Which biochemical change would reduce ketogenesis?

Options:
Increased glucagon activity
Increased insulin activity
Increased adipose lipolysis
Increased hepatic beta oxidation
Reduced carbohydrate availability

Correct Answer:
Increased insulin activity

Explanation:
Insulin suppresses adipose lipolysis and reduces fatty acid supply to liver, thereby decreasing ketogenesis.

MCQ 15

Question:
A lysosomal enzyme defect impairs degradation of glycosphingolipids. The most likely consequence is:

Options:
Reduced ketone body formation
Abnormal lipid accumulation in cells
Increased triacylglycerol storage only
Excess urea production
Failure of gluconeogenesis

Correct Answer:
Abnormal lipid accumulation in cells

Explanation:
Glycosphingolipids are degraded in lysosomes. Enzyme defects cause intracellular lipid storage and cellular dysfunction.

MCQ 16

Question:
Which statement best links triacylglycerol structure with its function?

Options:
It contains phosphate for membrane signaling
It contains three fatty acids for energy storage
It contains sphingosine for nerve conduction
It contains glucose for rapid ATP release
It contains nitrogen for protein synthesis

Correct Answer:
It contains three fatty acids for energy storage

Explanation:
Triacylglycerol contains glycerol esterified with three fatty acids, making it an efficient energy storage molecule.

MCQ 17

Question:
A membrane phospholipid is broken down to form signaling molecules. Which enzyme group is most directly involved?

Options:
Phospholipases
Transaminases
Dehydrogenases
Carboxylases
Hydroxylases

Correct Answer:
Phospholipases

Explanation:
Phospholipases degrade glycerophospholipids and release products that may participate in cell signaling.

MCQ 18

Question:
Which condition is most likely to increase ketone body production?

Options:
High insulin after a carbohydrate-rich meal
Prolonged fasting with low insulin level
Active glycogen synthesis after feeding
Reduced adipose hormone-sensitive lipase activity
Increased malonyl-CoA formation in liver

Correct Answer:
Prolonged fasting with low insulin level

Explanation:
Prolonged fasting lowers insulin and increases glucagon, promoting lipolysis, beta oxidation, and ketogenesis.

MCQ 19

Question:
A defect in glycosphingolipid metabolism would most directly disturb:

Options:
Cell recognition and neural function
Glycogen storage in liver
Ketone production in mitochondria
Ammonia detoxification in liver
Oxygen transport by hemoglobin

Correct Answer:
Cell recognition and neural function

Explanation:
Glycosphingolipids are important in cell recognition and are abundant in nervous tissue.

MCQ 20

Question:
In diabetic ketoacidosis, insulin therapy improves acidosis primarily by:

Options:
Increasing hepatic ketone synthesis
Increasing adipose fatty acid release
Reducing substrate supply for ketogenesis
Blocking renal glucose filtration
Stimulating sphingomyelin degradation

Correct Answer:
Reducing substrate supply for ketogenesis

Explanation:
Insulin inhibits lipolysis, reducing free fatty acid delivery to liver and decreasing ketone body production.

📌 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.