MCQs on Carbohydrates

Carbohydrates – Definition, Functions & Classification

Question 1

Which of the following best defines carbohydrates?

A. Organic compounds composed of amino acids
B. Organic compounds made up of carbon, hydrogen, and nitrogen
C. Organic compounds with carbon, hydrogen, and oxygen in a 1:2:1 ratio
D. Organic compounds consisting only of hydrocarbons

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Question 2

Which of the following is a monosaccharide?

A. Sucrose
B. Lactose
C. Maltose
D. Glucose

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Question 3

Carbohydrates serve all of the following functions EXCEPT:

A. Primary source of energy
B. Structural component of cell walls
C. Enzymatic catalyst
D. Precursor for nucleic acid synthesis

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Question 4

Which of the following carbohydrates is a disaccharide?

A. Glucose
B. Fructose
C. Galactose
D. Lactose

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Question 5

Which of the following is a homopolysaccharide?

A. Glycogen
B. Hyaluronic acid
C. Heparin
D. Chondroitin sulfate

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Question 6

Which carbohydrate is a ketose monosaccharide?

A. Glucose
B. Galactose
C. Fructose
D. Ribose

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Question 7

Cellulose differs from starch in that:

A. Cellulose is made of amino acids
B. Cellulose has α-1,4 glycosidic bonds
C. Cellulose is digestible by humans
D. Cellulose has β-1,4 glycosidic bonds

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Question 8

Which of the following polysaccharides is used as a storage form of glucose in humans?

A. Cellulose
B. Amylose
C. Glycogen
D. Chitin

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Question 9

Which of the following is incorrectly matched?

A. Sucrose – Glucose + Fructose
B. Lactose – Glucose + Galactose
C. Maltose – Glucose + Glucose
D. Cellulose – Glucose + Fructose

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Question 10

Which of the following is classified as a pentose sugar?

A. Glucose
B. Fructose
C. Ribose
D. Mannose

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✅ Answer Key

1. C. Organic compounds with carbon, hydrogen, and oxygen in a 1:2:1 ratio

2. D. Glucose

3. C. Enzymatic catalyst

4. D. Lactose

5. A. Glycogen

6. C. Fructose

7. D. Cellulose has β-1,4 glycosidic bonds

8. C. Glycogen

9. D. Cellulose – Glucose + Fructose

10. C. Ribose

 

Digestion and Absorption of Carbohydrates

Question 1

The digestion of carbohydrates begins in which part of the gastrointestinal tract?

A. Stomach
B. Mouth
C. Small intestine
D. Large intestine

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Question 2

Which enzyme is responsible for the initial digestion of starch in the oral cavity?

A. Maltase
B. Lactase
C. Salivary amylase
D. Pancreatic amylase

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Question 3

Salivary amylase is inactivated in which part of the digestive tract?

A. Esophagus
B. Mouth
C. Small intestine
D. Stomach

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Question 4

Which enzyme is secreted by the pancreas to continue carbohydrate digestion in the small intestine?

A. Sucrase
B. Pancreatic amylase
C. Lactase
D. Isomaltase

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Question 5

Disaccharides are broken down into monosaccharides by enzymes located:

A. In saliva
B. In the stomach lining
C. On the brush border of the small intestine
D. In the large intestine

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Question 6

Which enzyme is responsible for the digestion of lactose?

A. Maltase
B. Lactase
C. Sucrase
D. Amylase

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Question 7

The end products of carbohydrate digestion that are absorbed into the bloodstream are:

A. Disaccharides
B. Monosaccharides
C. Polysaccharides
D. Glycogen

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Question 8

The main site of carbohydrate absorption is:

A. Mouth
B. Stomach
C. Small intestine (jejunum)
D. Large intestine

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Question 9

Which of the following monosaccharides is absorbed by facilitated diffusion?

A. Glucose
B. Galactose
C. Fructose
D. Maltose

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Question 10

Glucose and galactose are absorbed into intestinal epithelial cells via:

A. Simple diffusion
B. Facilitated diffusion
C. Secondary active transport with sodium
D. Pinocytosis

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✅ Answer Key

1. B. Mouth

2. C. Salivary amylase

3. D. Stomach

4. B. Pancreatic amylase

5. C. On the brush border of the small intestine

6. B. Lactase

7. B. Monosaccharides

8. C. Small intestine (jejunum)

9. C. Fructose

10. C. Secondary active transport with sodium

Case-Based MCQs: Definition, Classification, Functions, Digestion & Absorption of Carbohydrates

Question 1

A 5-year-old boy presents with frequent bouts of diarrhea and abdominal cramps after drinking milk. His symptoms improve when milk is avoided.

Which carbohydrate-related disorder is likely?

A. Sucrase-isomaltase deficiency
B. Lactose intolerance
C. Glucose-galactose malabsorption
D. Fructose intolerance

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Question 2

A patient consumes a high-carbohydrate diet rich in starch. Which carbohydrate class primarily makes up starch?

A. Monosaccharides
B. Disaccharides
C. Polysaccharides
D. Oligosaccharides

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Question 3

During a biochemistry class, a student learns that carbohydrates have the general formula Cn(H2O)nC_n(H_2O)_nCn​(H2​O)n​. This means carbohydrates are composed of:

A. Carbon, hydrogen, oxygen in 1:1:1 ratio
B. Carbon, hydrogen, oxygen in 1:2:1 ratio
C. Carbon and oxygen only
D. Carbon, nitrogen, and oxygen

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Question 4

A 25-year-old patient has malabsorption symptoms. The enzyme sucrase is deficient, causing incomplete digestion of sucrose. Where is this enzyme primarily located?

A. Salivary glands
B. Pancreas
C. Brush border of small intestine
D. Stomach lining

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Question 5

A researcher studies the digestion of carbohydrates and finds that pancreatic amylase acts on which of the following substrates?

A. Monosaccharides
B. Disaccharides
C. Polysaccharides
D. Oligopeptides

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✅ Answer Key

1. B. Lactose intolerance

2. C. Polysaccharides

3. B. Carbon, hydrogen, oxygen in 1:2:1 ratio

4. C. Brush border of small intestine

5. C. Polysaccharides

Kreb’s Cycle with Regulation & Inhibitors

Question 1

Which molecule initiates the Krebs cycle by combining with oxaloacetate?

A. Acetyl-CoA
B. Pyruvate
C. Citrate
D. Malate

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Question 2

The rate-limiting enzyme of the Krebs cycle is:

A. Citrate synthase
B. Isocitrate dehydrogenase
C. α-Ketoglutarate dehydrogenase
D. Succinate dehydrogenase

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Question 3

Which of the following is an allosteric activator of isocitrate dehydrogenase?

A. ATP
B. NADH
C. ADP
D. Succinyl-CoA

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Question 4

Which compound inhibits the enzyme α-ketoglutarate dehydrogenase?

A. NADH
B. ADP
C. Ca²⁺
D. Citrate

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Question 5

Fluoroacetate is a potent toxin that inhibits the Krebs cycle by forming fluorocitrate. Which enzyme does fluorocitrate inhibit?

A. Citrate synthase
B. Aconitase
C. Succinate dehydrogenase
D. Malate dehydrogenase

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Question 6

Which intermediate of the Krebs cycle is involved in substrate-level phosphorylation to produce GTP or ATP?

A. Succinate
B. Succinyl-CoA
C. Fumarate
D. Succinate thiokinase (succinyl-CoA synthetase) acts on this

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Question 7

NADH and ATP act as:

A. Positive regulators of the Krebs cycle
B. Negative regulators of the Krebs cycle
C. Substrates for the cycle
D. None of the above

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Question 8

The enzyme succinate dehydrogenase is unique because:

A. It uses FAD as a cofactor
B. It is located in the mitochondrial matrix only
C. It produces NADH directly
D. It is not part of the electron transport chain

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Question 9

Which of the following is NOT a product of one turn of the Krebs cycle?

A. NADH
B. FADH2
C. ATP (or GTP)
D. Glucose

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Question 10

High levels of which molecule inhibit citrate synthase activity?

A. NAD+
B. Citrate
C. ADP
D. Ca²⁺

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✅ Answer Key

1. A. Acetyl-CoA

2. B. Isocitrate dehydrogenase

3. C. ADP

4. A. NADH

5. B. Aconitase

6. D. Succinate thiokinase (succinyl-CoA synthetase) acts on this

7. B. Negative regulators of the Krebs cycle

8. A. It uses FAD as a cofactor

9. D. Glucose

10. B. Citrate

 

Gluconeogenesis and Cori Cycle

Question 1

Which of the following is the main site of gluconeogenesis?

A. Skeletal muscle
B. Kidney cortex
C. Liver
D. Brain

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Question 2

Which of the following substrates is not used in gluconeogenesis?

A. Lactate
B. Glycerol
C. Alanine
D. Acetyl-CoA

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Question 3

Which enzyme converts pyruvate to oxaloacetate in gluconeogenesis?

A. Pyruvate kinase
B. Pyruvate dehydrogenase
C. Pyruvate carboxylase
D. Malate dehydrogenase

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Question 4

Which coenzyme is required for the function of pyruvate carboxylase?

A. Thiamine
B. NAD⁺
C. Biotin
D. Riboflavin

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Question 5

Which of the following glycolytic enzymes is bypassed in gluconeogenesis by the enzyme fructose-1,6-bisphosphatase?

A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Pyruvate kinase
D. Enolase

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Question 6

Which enzyme catalyzes the conversion of glucose-6-phosphate to free glucose in gluconeogenesis?

A. Glucokinase
B. Phosphoglucomutase
C. Glucose-6-phosphatase
D. Glucose oxidase

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Question 7

Gluconeogenesis is stimulated during:

A. Fed state
B. Hypoglycemia and fasting
C. After carbohydrate-rich meal
D. Insulin excess

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Question 8

Which hormone stimulates gluconeogenesis?

A. Insulin
B. Epinephrine
C. Glucagon
D. Both B and C

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Question 9

The Cori cycle involves the recycling of:

A. Alanine
B. Lactate
C. Glycerol
D. Glucose

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Question 10

Which of the following gluconeogenic steps takes place in mitochondria?

A. Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
B. Conversion of glucose-6-phosphate to glucose
C. Conversion of pyruvate to oxaloacetate
D. Conversion of oxaloacetate to phosphoenolpyruvate

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✅ Answer Key

1. C. Liver

2. D. Acetyl-CoA

3. C. Pyruvate carboxylase

4. C. Biotin

5. B. Phosphofructokinase-1 (PFK-1)

6. C. Glucose-6-phosphatase

7. B. Hypoglycemia and fasting

8. D. Both B and C

9. B. Lactate

10. C. Conversion of pyruvate to oxaloacetate

 

Glycogen Metabolism & Glycogen Storage Disorders (GSDs)

Question 1

Glycogen is primarily stored in which two tissues?

A. Liver and kidney
B. Liver and skeletal muscle
C. Muscle and brain
D. Brain and adipose tissue

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Question 2

The enzyme responsible for breaking α-1,4-glycosidic bonds in glycogen is:

A. Glycogen synthase
B. Glycogen phosphorylase
C. Debranching enzyme
D. Phosphoglucomutase

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Question 3

Which enzyme introduces α-1,6 branches during glycogenesis?

A. Branching enzyme (amylo-1,4 → 1,6-transglucosidase)
B. Glycogen phosphorylase
C. Debranching enzyme
D. Hexokinase

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Question 4

Which hormone stimulates glycogenolysis in the liver during fasting?

A. Insulin
B. Glucagon
C. Epinephrine
D. Both B and C

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Question 5

Which of the following enzymes is deficient in Von Gierke’s disease (GSD type I)?

A. Glucose-6-phosphatase
B. Glycogen phosphorylase
C. Acid maltase
D. Debranching enzyme

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Question 6

A child presents with hepatomegaly and severe fasting hypoglycemia. Lab tests show increased glycogen in the liver.
Which glycogen storage disorder is most likely?

A. McArdle disease
B. Pompe disease
C. Von Gierke disease
D. Cori disease

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Question 7

Which glycogen storage disorder is caused by a deficiency of muscle glycogen phosphorylase?

A. Von Gierke disease
B. McArdle disease
C. Pompe disease
D. Andersen disease

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Question 8

In Pompe disease (GSD type II), the defective enzyme is:

A. Glycogen phosphorylase
B. Debranching enzyme
C. Lysosomal α-1,4-glucosidase (acid maltase)
D. Glucose-6-phosphatase

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Question 9

The debranching enzyme has which two catalytic activities?

A. Phosphorylation and deamination
B. Transferase and α-1,6-glucosidase
C. Kinase and mutase
D. Isomerase and oxidase

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Question 10

Which of the following is TRUE about glycogen synthase?

A. It adds glucose to glycogen via α-1,4 linkages
B. It is active in its phosphorylated form
C. It is stimulated by glucagon
D. It breaks down glycogen into glucose

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✅ Answer Key

1. B. Liver and skeletal muscle

2. B. Glycogen phosphorylase

3. A. Branching enzyme (amylo-1,4 → 1,6-transglucosidase)

4. D. Both B and C

5. A. Glucose-6-phosphatase

6. C. Von Gierke disease

7. B. McArdle disease

8. C. Lysosomal α-1,4-glucosidase (acid maltase)

9. B. Transferase and α-1,6-glucosidase

10. A. It adds glucose to glycogen via α-1,4 linkages

HMP Shunt – Metabolic and Clinical Significance

Question 1

The primary function of the HMP shunt in cells is to:

A. Generate ATP
B. Synthesize glucose
C. Produce NADPH and ribose-5-phosphate
D. Convert pyruvate to acetyl-CoA

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Question 2

The HMP shunt occurs mainly in:

A. Nucleus
B. Mitochondria
C. Cytoplasm
D. Endoplasmic reticulum

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Question 3

Which enzyme catalyzes the first irreversible step of the oxidative phase of the HMP shunt?

A. Transaldolase
B. Transketolase
C. Glucose-6-phosphate dehydrogenase (G6PD)
D. Phosphofructokinase

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Question 4

NADPH produced in the HMP shunt is required for all the following EXCEPT:

A. Fatty acid synthesis
B. Cholesterol synthesis
C. Oxidative phosphorylation
D. Maintaining reduced glutathione in RBCs

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Question 5

A deficiency of glucose-6-phosphate dehydrogenase (G6PD) can lead to:

A. Ketoacidosis
B. Hemolytic anemia
C. Hyperglycemia
D. Scurvy

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Question 6

Which of the following is a non-oxidative phase enzyme of the HMP shunt?

A. G6PD
B. 6-Phosphogluconate dehydrogenase
C. Transketolase
D. Gluconolactonase

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Question 7

Thiamine (vitamin B1) is a cofactor for which HMP shunt enzyme?

A. Glucose-6-phosphate dehydrogenase
B. Transketolase
C. Transaldolase
D. Hexokinase

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Question 8

Which of the following cell types primarily relies on the HMP shunt for NADPH production?

A. Skeletal muscle
B. Erythrocytes
C. Neurons
D. Hepatocytes

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Question 9

The ribose-5-phosphate produced in the HMP shunt is used for:

A. Protein synthesis
B. ATP generation
C. Nucleotide and nucleic acid synthesis
D. Lipid transport

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Question 10

In G6PD deficiency, hemolysis is triggered by:

A. Vitamin C supplementation
B. High-protein diet
C. Oxidative stress from drugs or infections
D. Low-fat diet

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✅ Answer Key

1. C. Produce NADPH and ribose-5-phosphate

2. C. Cytoplasm

3. C. Glucose-6-phosphate dehydrogenase (G6PD)

4. C. Oxidative phosphorylation

5. B. Hemolytic anemia

6. C. Transketolase

7. B. Transketolase

8. B. Erythrocytes

9. C. Nucleotide and nucleic acid synthesis

10. C. Oxidative stress from drugs or infections

 

Hormonal Regulation of Blood Sugar

Question 1

Which hormone is primarily responsible for lowering blood glucose levels?

A. Glucagon
B. Insulin
C. Cortisol
D. Epinephrine

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Question 2

Which of the following hormones increases blood glucose by stimulating glycogenolysis and gluconeogenesis?

A. Insulin
B. Growth hormone
C. Glucagon
D. Thyroxine

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Question 3

Insulin facilitates glucose uptake primarily by increasing the number of:

A. GLUT-1 transporters
B. GLUT-2 transporters
C. GLUT-4 transporters
D. Sodium-glucose co-transporters

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Question 4

Which of the following hormones is secreted during stress and contributes to increased blood glucose?

A. Parathyroid hormone
B. Melatonin
C. Epinephrine
D. Calcitonin

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Question 5

Which of the following does not increase blood glucose?

A. Cortisol
B. Glucagon
C. Growth hormone
D. Insulin

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Question 6

Which pancreatic cells secrete insulin?

A. Alpha cells
B. Beta cells
C. Delta cells
D. F cells

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Question 7

Which hormone acts antagonistically to insulin?

A. Estrogen
B. Testosterone
C. Glucagon
D. Prolactin

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Question 8

The action of insulin on carbohydrate metabolism includes:

A. Increased gluconeogenesis
B. Increased glucose uptake in muscles and adipose tissue
C. Increased glycogenolysis
D. Increased lipolysis

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Question 9

In Type I diabetes mellitus, blood glucose remains high due to:

A. Excess insulin secretion
B. Defective insulin receptors
C. Autoimmune destruction of β-cells
D. Increased insulin sensitivity

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Question 10

Which hormone is responsible for maintaining blood glucose during prolonged fasting?

A. Insulin
B. Leptin
C. Cortisol
D. Erythropoietin

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✅ Answer Key

1. B. Insulin

2. C. Glucagon

3. C. GLUT-4 transporters

4. C. Epinephrine

5. D. Insulin

6. B. Beta cells

7. C. Glucagon

8. B. Increased glucose uptake in muscles and adipose tissue

9. C. Autoimmune destruction of β-cells

10. C. Cortisol

Diabetes Mellitus – Types, Diagnosis, Metabolic Changes, Complications & Management

Question 1

Which of the following best explains the mechanism of glycosuria in uncontrolled diabetes mellitus?

A. Increased renal threshold for glucose
B. Impaired insulin receptor sensitivity
C. Glucose filtered exceeds renal tubular reabsorption capacity
D. Decreased glomerular filtration rate

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Question 2

Type 2 Diabetes Mellitus (T2DM) is most commonly associated with:

A. Insulin deficiency only
B. Autoimmune factors
C. Insulin resistance and relative insulin deficiency
D. Viral infections in early life

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Question 3

Which of the following is a diagnostic criterion for diabetes mellitus?

A. Fasting plasma glucose ≥ 100 mg/dL
B. HbA1c ≥ 6.5%
C. Random blood glucose < 140 mg/dL
D. OGTT (2-hour post-load glucose) < 140 mg/dL

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Question 4

Which metabolic abnormality is most commonly seen in uncontrolled diabetes mellitus?

A. Hypoglycemia
B. Hyperlipidemia
C. Hypokalemia
D. Hypercalcemia

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Question 5

Which of the following is NOT a microvascular complication of diabetes?

A. Diabetic nephropathy
B. Diabetic neuropathy
C. Diabetic retinopathy
D. Coronary artery disease

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Question 6

Which of the following best explains polyuria in diabetes?

A. Increased protein catabolism
B. Ketone body accumulation
C. Osmotic diuresis due to glucosuria
D. Increased urea excretion

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Question 7

Renal glycosuria is characterized by:

A. High blood glucose with absent urinary glucose
B. Normal blood glucose with presence of glucose in urine
C. Low blood glucose with ketonuria
D. High insulin levels with glucosuria

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Question 8

Which of the following investigations is most appropriate for long-term monitoring of glycemic control in a diabetic patient?

A. Fasting blood glucose
B. Oral glucose tolerance test (OGTT)
C. HbA1c (Glycated hemoglobin)
D. Random blood glucose

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Question 9

Which of the following is an early sign of diabetic nephropathy?

A. Elevated creatinine
B. Macroalbuminuria
C. Microalbuminuria
D. Hematuria

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Question 10

Ketoacidosis is a complication seen primarily in:

A. Type 2 DM
B. Gestational diabetes
C. Type 1 DM
D. MODY (Maturity-onset diabetes of the young)

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✅ Answer Key

1. C. Glucose filtered exceeds renal tubular reabsorption capacity

2. C. Insulin resistance and relative insulin deficiency

3. B. HbA1c ≥ 6.5%

4. B. Hyperlipidemia

5. D. Coronary artery disease

6. C. Osmotic diuresis due to glucosuria

7. B. Normal blood glucose with presence of glucose in urine

8. C. HbA1c (Glycated hemoglobin)

9. C. Microalbuminuria

10. C. Type 1 DM

 

Revision Questions

1. An 8‑month‑old child presents with hypoglycemia between feeds, hepatomegaly, lactic acidosis, and ketosis. Which enzyme deficiency is most likely?
   A. Glucose‑6‑phosphatase
   B. Phosphofructokinase
   C. Glycogen synthase
   D. Branching enzyme

2. Which of the following steps in glycolysis is irreversible?
   A. 3‑phosphoglycerate → 2‑phosphoglycerate
   B. Phosphoenolpyruvate → Pyruvate
   C. Glyceraldehyde‑3‑phosphate → 1,3‑bisphosphoglycerate
   D. Fructose‑6‑phosphate → Fructose‑1,6‑bisphosphate

3. The enzyme which is common to both glycolysis and gluconeogenesis is:
   A. Phosphofructokinase‑1
   B. Hexokinase/Glucokinase
   C. Pyruvate kinase
   D. Fructose‑1,6‑bisphosphatase

4. Which of the following is the rate‑limiting enzyme of gluconeogenesis?
   A. Pyruvate carboxylase
   B. Phosphoenolpyruvate carboxykinase (PEPCK)
   C. Fructose‑1,6‑bisphosphatase
   D. Glucose‑6‑phosphatase

5. In which tissue(s) does gluconeogenesis occur?
   A. Liver only
   B. Liver and kidney
   C. Liver, kidney and muscle
   D. All tissues

6. The major control point in glycolysis is the enzyme:
   A. Hexokinase
   B. Phosphofructokinase‑1 (PFK‑1)
   C. Glyceraldehyde‑3‑phosphate dehydrogenase
   D. Enolase

7. Which of the following is NOT a product of the Pentose Phosphate (Hexose Monophosphate) pathway?
   A. Ribose‑5‑phosphate
   B. NADPH
   C. Fructose‑1,6‑bisphosphate
   D. Erythrose‑4‑phosphate

8. In G6PD deficiency, which of the following is true?
   A. There is decreased production of NADPH in red cells
   B. Increased glutathione recycling
   C. Decreased susceptibility to oxidative stress
   D. Increased ability to reduce methemoglobin

9. Which transporter type is insulin‑dependent for glucose uptake?
   A. GLUT‑1
   B. GLUT‑2
   C. GLUT‑3
   D. GLUT‑4

10. Fluoroacetate poisoning inhibits which enzyme of TCA cycle by making fluorocitrate?
    A. Citrate synthase
    B. Aconitase
    C. Isocitrate dehydrogenase
    D. α‑Ketoglutarate dehydrogenase

11. During high demand (like after carbohydrate meal), which of the following enzymes in liver is activated to promote glycolysis?
    A. Glucokinase
    B. Fructose‑1,6‑bisphosphatase
    C. PEPCK
    D. Glucose‑6‑phosphatase

12. The direct precursor for gluconeogenesis for the formation of phosphoenolpyruvate (PEP) is:
    A. Pyruvate
    B. Oxaloacetate
    C. Fumarate
    D. Lactate

13. Which of the following enzymes is responsible for the “branching” point in glycogen?
    A. Glycogen synthase
    B. Debranching enzyme
    C. Branching enzyme (α‑1,4 → α‑1,6 glucan transferase)
    D. Glycogen phosphorylase

14. What is the net yield of ATP from one molecule of glucose via anaerobic glycolysis (in muscle)?
    A. 2 ATP
    B. 4 ATP
    C. 32 ATP
    D. 36 ATP

15. Which enzyme converts glucose‑6‑phosphate to 6‑phosphogluconate in the oxidative phase of HMP pathway?
    A. Glucose‑6‑phosphate dehydrogenase
    B. Phosphogluconate dehydrogenase
    C. 6‑phosphogluconolactonase
    D. Transketolase

16. Which cofactor is required for transketolase in non‑oxidative HMP pathway?
    A. NADPH
    B. NAD+
    C. Thiamine pyrophosphate (TPP)
    D. Biotin

17. In fasting state, which hormone induces gluconeogenesis?
    A. Insulin
    B. Glucagon
    C. Growth hormone
    D. Aldosterone

18. What is the function of glucose‑6‑phosphatase?
    A. Converts glucose to glucose‑6‑phosphate
    B. Converts glucose‑6‑phosphate to glucose
    C. Converts fructose‑6‑phosphate to fructose‑1,6‑bisphosphate
    D. Converts fructose‑1,6‑bisphosphate to fructose‑6‑phosphate

19. Which glycolytic enzyme is inhibited by fluoride (in blood collection tubes)?
    A. Hexokinase
    B. Enolase
    C. Phosphofructokinase
    D. Aldolase

20. The Rapoport–Leubering shunt in red blood cells produces:
    A. 2,3‑bisphosphoglycerate
    B. 1,3‑bisphosphoglycerate
    C. Phosphoenolpyruvate
    D. Pyruvate

21. Which of the following is the enzyme in glycogen breakdown that removes glucose units from non‑reducing ends?
    A. Glycogen phosphorylase
    B. Debranching enzyme
    C. Branching enzyme
    D. Glycogen synthase

22. During intense exercise in muscle, pyruvate is converted to lactate by which enzyme?
    A. Lactate dehydrogenase
    B. Pyruvate carboxylase
    C. Pyruvate kinase
    D. Alanine aminotransferase

23. Which of these is NOT a gluconeogenic precursor?
    A. Glycerol
    B. Lactate
    C. Palmitic acid (a long chain fatty acid)
    D. Amino acids

24. What is the fate of fructose when it enters glycolysis in the liver via fructokinase pathway?
    A. Fructose → Fructose‑6‑phosphate directly
    B. Fructose → Fructose‑1‑phosphate → DHAP + glyceraldehyde
    C. Fructose → Fructose‑2,6‑bisphosphate
    D. Fructose → Fructose‑1,6‑bisphosphate directly

25. Which of the following enzymes is allosterically activated by AMP?
    A. Phosphofructokinase‑1 (PFK‑1)
    B. Fructose‑1,6‑bisphosphatase
    C. Hexokinase
    D. Glucose‑6‑phosphate dehydrogenase

26. Pyruvate dehydrogenase complex is inhibited by which of the following?
    A. Acetyl‑CoA & NADH accumulation
    B. High levels of AMP
    C. High levels of ADP
    D. High levels of CoA

27. The “obligate” NADPH source for fatty acid synthesis is from which pathway?
    A. Glycolysis
    B. TCA cycle
    C. HMP (Pentose Phosphate) pathway
    D. Electron transport chain

28. Which enzyme catalyzes the conversion of glucose‑1‑phosphate to UDP‑glucose during glycogenesis?
    A. UDP‑glucose pyrophosphorylase
    B. Glycogen synthase
    C. Phosphoglucomutase
    D. Branching enzyme

29. After a meal, high blood glucose leads to activation of which enzyme in the liver that increases F‑2,6‑BP and thus stimulates glycolysis?
    A. PFK‑1
    B. PFK‑2 / Fructose‑2,6‑bisphosphatase (the bifunctional enzyme)
    C. Pyruvate kinase
    D. Glucose‑6‑phosphatase

30. What is the theoretical maximum ATP yield (net) per molecule of glucose fully oxidized (aerobic respiration) in human cells (accounting approx. NADH, FADH₂ yields)?
    A. ~30 ATP
    B. ~32 ATP
    C. ~36 ATP
    D. ~38 ATP

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Answer Key