COLLEGE of MEDICINE AND HEALTH SCIENCES

Department of Medical Biochemistry, Molecular SCHOOL

Biologyofand Genetics
MEDICINE AND PHARMACY
Module: Structural Biochemistry, Nutrition and Basic Metabolism

CAT-2
Carbohydrates Metabolism, Lipid Metabolism and Bioenergetics

General Directions:
⇒ Write your name and registration number on space provided for you on each page of
examination paper and answer sheet booklet.
⇒ The examination consists of 4 parts (5 Definitions; 30 MCQs; 9 Matching and 3 Essay
questions) on 7 pages.
⇒ Attempt all questions and give your answers on the space provided in answer sheet
booklet.
⇒ Switch off your cell phone.
⇒ Any attempt to copy from other student or electronic material results in disqualification
and a mark of zero will be awarded.
⇒ The time given for the exam is 2hrs.

Prepared by:
1. Assoc. Prof Mala George
2. Dr. Elizabeth Gori
3. Dr Samuel
3. Dr. Samson Awotunde
4. Mr. Mugisha Jean Claude

Moderated by:
Dr. Tolessa Muleta
Part I: Definition/5arks:

Define the following terms or phrases and write your answers on the space provided for you

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Here’s a summary of the biochemical terms:

1. Lactic Acidosis: Excess lactic acid in the body, often from intense exercise or low oxygen, causing
muscle pain and fatigue.

2. Ketoacidosis: High levels of ketones in the blood, leading to acidity, commonly seen in
uncontrolled diabetes or prolonged fasting, with symptoms like nausea.

3. Amphibolism: A metabolic process that involves both breaking down and building up molecules,
allowing efficient nutrient use.

4. Lactose Intolerance: Inability to digest lactose due to a lack of the enzyme lactase, resulting in
gas, bloating, and diarrhea after dairy consumption.

5. Ketolysis: The breakdown of ketone bodies for energy, parti cularly when glucose
availability is low, such as during fasting or low-carb diets.

Part II: MCQs /30marks

Choose the correct answer and write your answer on the space against each question
___C` QWA_1. A 4-month-old boy presents with frequent episodes of weakness and is diagnosed with
an enzyme deficiency of glucose 6-phosphatase, which is normally only expressed in which of the
following?
(A) Liver and muscle
(B) Liver and brain
(C) Liver and kidney
(D) Liver and adipose tissue

__A__2. A blood screen for galactosemia is positive, and lactose-containing substances are removed from
the diet. Lactose is toxic in this case because

(A) Galactose is converted to the toxic substance galactitol (dulcitol)

(B) Galactose competes for glucose during hepatic glycogen synthesis
(C) Galactose is itself toxic in even small amounts
(D) Glucose metabolism is shut down by excess galactose

___C_3. An African medical student studying in the United States develops hemolytic anemia after
taking the oxidizing antimalarial drug pamaquine. This severe reaction is most likely due to

(A) Glucose-6-phosphate dehydrogenase deficiency

(B) Concomitant scurvy

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 (C) Vitamin C deficiency
(D) Glycogen phosphorylase deficiency

___B_4. McArdle’s disease causes muscle cramps and muscle fatigue with increased muscle glycogen.
Which of the following enzymes is deficient?

(A) Muscle glycogen synthetase

(B) Muscle phosphorylase
(C) Muscle hexokinase
(D) Muscle debranching enzyme

__B__5. A 5-year-old boy is diagnosed with primary carnitine deficiency. What is the primary problem
with this disorder?
(A) Activation of fatty acids
(B) Impaired transport of long-chain fatty acids
(C) β-Oxidation
(D) α-Oxidation

__B__6. Chylomicrons, intermediate-density lipoproteins (IDLs), low-density lipoproteins (LDLs), and

very-low-density lipoproteins (VLDLs) are all serum lipoproteins. What is the correct ordering of these
particles from the lowest to the highest density?

(A) LDLs, IDLs, VLDLs, chylomicrons

(B) Chylomicrons, VLDLs, IDLs, LDLs
(C) VLDLs, IDLs, LDLs, chylomicrons
(D) Chylomicrons, IDLs, VLDLs, LDLs

__C__7. In humans, the formation of the fatty acid C-18-∆9, ∆12 can be derived from which of the
following?
(A) C-18 cis-∆9
(B) C-18 cis-∆6
(C) C-16 cis-∆6, ∆9
(D) C-18 cis-∆9, ∆12

__D__8. A 38-year-old woman is found to have an obstructing gallstone in the common bile duct. What
is clinical implication of this obstruction?
(A) Increased formation of chylomicrons
(B) Increased recycling of bile salts
(C) Increased excretion of bile salts
(D) Increased excretion of fat in the feces

___B_9. A biochemistry graduate student isolates all the enzymes of the TCA cycle and adds OAA and
acetyl CoA, including the appropriate energy precursors, cofactors, and water. Which of the following
will NOT be a direct product of his experiment?
(A) GTP
(B) NADPH
(C) CO2
(D) FADH2

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___D_10. Which of the following is NOT antioxidant enzymes that scavenge or eliminate a variety of
free radicals including those generated during Electron Transport Chain.
(A) Superoxide dismutase
(B) Catalase
(C) Hydrogen peroxidase
(D) Glutathione

__C__11. Which of the following is not related to the pyruvic acid oxidation?
(A) Decarboxylation
(B) Addition of Co-A
(C) Oxidation of NAD+
(D) Oxidation of pyruvate

__B__12. The reaction of Oxidizing Malate with NAD+ as a coenzyme generates

(A) ADP+ ATP+ Oxaloacetate
(B) NADH+ H+ + Oxaloacetate
(C) Acetate + NADH
(D) Oxaloacetate+ NADPH

__C__13. Which of the following lipoproteins is produced via the exogenous lipoprotein pathway?
(A) High density lipoproteins
(B) Low density lipoproteins
(C) Chylomicrons
(D) Low density lipoproteins
__D__14. De novo fatty acid synthesis usually signifies which of the following?
(A) An excess of fat intake
(B) A depletion of energy yielding substrates
(C) Only occurs with prolonged fasting
(D) An excess of energy yielding substrates
__B__15. Which of the following enzymes is responsible for the initial step in β-oxidation of fatty acids?
(A) Acetyl-CoA C-acetyltransferase
(B) Carnitine palmitoyltransferase I
(C) Acyl-CoA dehydrogenases
(D) Acetyl-CoA carboxylase
__C__16. Which of the following is not produced during the one round of β-oxidation for a saturated
fatty acid?
(A) FADH2
(B) Acetyl CoA
(C) Glycerol
(D) NADH

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__D__17. Iron–sulfur clusters [Fe–S] are the key prosthetic group that carry electrons in all of the below
except:
(A) Succinate –CoQ reductase
(B) NADH – CoQ reductase
(C) CoQH2-cytochrome c reductase
(D) Cytochrome c oxidase

__A__18. Which of the following is the right combination of energy–rich molecules produced from one
molecule of Acetyl-CoA when is metabolized by the citric acid cycle?
(A) 3 NADH + 1 FADH2 + 1 GTP
(B) 2 NADH + 2 FADH2 + 1 GTP
(C) 4 NADH + 1 FADH2 + 1 GTP
(D) 3 NADH + 1 GTP
____19. What is the primary function of liver glycogen?
(A) Provide glucose-6-phosphate for muscle energy
(B) Maintain blood glucose levels, especially during fasting
(C) Store ATP for muscle contraction
(D) Act as an immediate source of energy during exercise

__A__20. What is the importance of glucose phosphorylation at the start of glycolysis?

(A) To trap glucose inside the cell
(B) To increase ATP production
(C) To decrease enzyme activity
(D) To activate pyruvate

__B__21. The pentose phosphate pathway (HMP shunt) primarily produces which of the following?
(A) NADH and ATP
(B) NADPH and ribose-5-phosphate
(C) FADH2 and Acetyl-CoA
(D) Pyruvate and lactate

__C__22. Which ion is necessary for the activation of salivary amylase?

(A) Sodium (Na⁺)
(B) Calcium (Ca²⁺)
(C) Chloride (Cl⁻)
(D) Potassium (K⁺)

___C_23. Glycolysis produces ATP by

(A) Phosphorylating organic molecules in the priming reactions.
(B) The production of glyceraldehyde 3-phosphate.
(C) Substrate-level phosphorylation.
(D) The reduction of NAD+ to NADH.

__C__24. What is the importance of fermentation to cellular metabolism?

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 (A) It generates glucose for the cell in the absence of O2
(B) It oxidises NADH to NAD+ during electron transport.
(C) It oxidises NADH to NAD+ in the absence of O2
(D) It reduces NADH to NAD+ in the absence of O2

__D__25. When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it
contracts anaerobically because:
(A) Muscle is metabolically less active under aerobic than anaerobic conditions.
(B) The lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
(C) Under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate
pathway, which does not produce lactate.
(D) Under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidised
by the citric acid cycle rather than reduced to lactate.
__D__26. Which of the following statements is incorrect?
(A) In anaerobic muscle, pyruvate is converted to lactate.
(B) In yeast growing anaerobically, pyruvate is converted to ethanol.
(C) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis.
(D) Under anaerobic conditions, pyruvate does not form because glycolysis does not occur.

_C___27. Which of the following is a component of lung or pulmonary surfactant found in the
extracellular lipid layer lining the pulmonary alveoli?
(A) Cholesterol
(B) Cerebrosides
(C) Phosphatidylcholine
(D) Sphingomyelins

__C__28. Which Phospholipase hydrolyze hydrolyzes the fatty acid of glycerolphospholipids at C1.?
(A) Phospholipase C
(B) Phospholipase A2
(C) Phospholipase A1
(D) Phospholipase D

_B___29. The Beta oxidation of 14 carbon fatty acid produces:

(A) 8 AcetylcoA
(B) 7 AcetylcoA
(C) 6 AcetylcoA
(D) 5 AcetylcoA

__B__30. The deficiency of sphingomyelinase deficiency causes:

(A) Tay-Sachs Disease
(B) Niemann-Pick Disease
(C) Fabry’s Disease
(D) Gaucher’s Disease

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PART III: Matching Questions/9makrs

Choose the best answer from the items listed under column C and match to those under column A and
write your answers on column B.

Column A Column B Column C

1. Arachidonic Acid K A. Endergonic
2. Insulin Dependent Transporter H B. 2,4 Dinitrophenol
3. HMG-COA reductase inhibitors G C. GLUT-3
4. Release energy in the form of ATP D D. Exergonic
5. Fructose 2,6-bisphosphate F E. Pyridoxal phosphate.
6. Uncouplers B F. Activates phosphofructokinase-1 (PFK-1).
7. Glycogen phosphorylase E G. Statins
8. Respiratory Distress Syndrome J H. GLUT-4
9. Acetone L J. Phosphatidylcholine
K. Prostaglandins
L. Gas

1. **Arachidonic Acid**
**K. Prostaglandins**

2. **Insulin Dependent Transporter**

**H. GLUT-4**

3. **HMG-COA reductase inhibitors**

**G. Statins**

4. **Release energy in the form of ATP**

**D. Exergonic**

5. **Fructose 2,6-bisphosphate**
**F. Activates phosphofructokinase-1 (PFK-1)**

6. **Uncouplers**
**B. 2,4 Dinitrophenol**

7. **Glycogen phosphorylase**
**E. Pyridoxal phosphate**

8. **Respiratory Distress Syndrome**

**J. Phosphatidylcholine**

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9. **Acetone**
**L. Gas**

Part IV: Short Answer Questions/6marks

Give brief and clear answers for the following questions

1. State TWO differences between inhibitors and uncouplers of Electron Transport Chain and
Oxidative Phosphorylation reaction (2marks)

1. Differences Between Inhibitors and Uncouplers of the Electron Transport Chain

and Oxidative Phosphorylation

Mechanism of Action:

Inhibitors directly block the electron transport chain (ETC) complexes, preventing electron
flow and ATP synthesis (e.g., cyanide inhibits cytochrome c oxidase).

Uncouplers dissipate the proton gradient across the mitochondrial membrane, allowing
protons to re-enter the mitochondrial matrix without generating ATP, thus uncoupling
oxidative phosphorylation from the ETC (e.g., 2,4-dinitrophenol).

Effect on ATP Production:

Inhibitors lead to a decrease in ATP production due to halted electron transport and reduced
proton pumping.

Uncouplers can lead to increased oxygen consumption without ATP production, as the energy
from the proton gradient is released as heat instead of being used for ATP synthesis.

2. Discuss how deficiency of pyruvate kinase is related to hemolytic anemia. (2marks)

Pyruvate kinase deficiency leads to reduced conversion of phosphoenolpyruvate to pyruvate in

glycolysis, resulting in decreased ATP production. Red blood cells (RBCs) rely heavily on glycolysis
for ATP to maintain their shape and functionality. Insufficient ATP leads to RBC membrane
instability, causing hemolysis (destruction of red blood cells). This hemolytic anemia is
characterized by a decrease in red blood cell count and increased levels of bilirubin due to the
breakdown of hemoglobin from lysed cells.

3. Describe hyperlipidemia and state two biochemical result of the condition. (2marks)

Hyperlipidemia refers to elevated levels of lipids (fats) in the bloodstream, which can include cholesterol
and triglycerides. This condition can be caused by genetic factors, poor diet, obesity, diabetes, or other
underlying health issues.

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Biochemical Results:

Elevated Triglycerides: High levels of triglycerides in the blood can increase the risk of pancreatitis and
cardiovascular diseases.

Increased LDL Cholesterol: Elevated low-density lipoprotein (LDL) cholesterol levels contribute to
atherosclerosis, increasing the risk of heart disease and stroke.

….……………………….. END……………….

DESCRIPTION

Here are the selected answers for each question:

1. **C**
A 4-month-old boy presents with frequent episodes of weakness and is diagnosed with an enzyme
deficiency of glucose 6-phosphatase, which is normally only expressed in which of the following?
**(C) Liver and kidney**

2. **A**
A blood screen for galactosemia is positive, and lactose-containing substances are removed from the
diet. Lactose is toxic in this case because:
**(A) Galactose is converted to the toxic substance galactitol (dulcitol)**

3. **C**
An African medical student studying in the United States develops hemolytic anemia after taking the
oxidizing antimalarial drug pamaquine. This severe reaction is most likely due to:
**(A) Glucose-6-phosphate dehydrogenase deficiency**

4. **B**
McArdle’s disease causes muscle cramps and muscle fatigue with increased muscle glycogen. Which of
the following enzymes is deficient?
**(B) Muscle phosphorylase**
Here are the selected answers for each question:

5. **B**

9
 A 5-year-old boy is diagnosed with primary carnitine deficiency. What is the primary problem with this
disorder?
**(B) Impaired transport of long-chain fatty acids**

6. **B**
Chylomicrons, intermediate-density lipoproteins (IDLs), low-density lipoproteins (LDLs), and very-
low-density lipoproteins (VLDLs) are all serum lipoproteins. What is the correct ordering of these
particles from the lowest to the highest density?
**(B) Chylomicrons, VLDLs, IDLs, LDLs**

7. **C**
In humans, the formation of the fatty acid C-18-∆9, ∆12 can be derived from which of the following?
**(C) C-16 cis-∆6, ∆9**

8. **D**
A 38-year-old woman is found to have an obstructing gallstone in the common bile duct. What is the
clinical implication of this obstruction?
**(D) Increased excretion of fat in the feces**

9. **B**
A biochemistry graduate student isolates all the enzymes of the TCA cycle and adds OAA and acetyl
CoA, including the appropriate energy precursors, cofactors, and water. Which of the following will NOT
be a direct product of his experiment?
**(B) NADPH**

10. **D**
Which of the following is NOT an antioxidant enzyme that scavenges or eliminates a variety of free
radicals including those generated during Electron Transport Chain?
**(D) Glutathione**
Here are the selected answers for each question:

11. **C**
Which of the following is not related to the pyruvic acid oxidation?
**(C) Oxidation of NAD+**

12. **B**
The reaction of oxidizing malate with NAD+ as a coenzyme generates:
**(B) NADH + H+ + Oxaloacetate**

13. **C**
Which of the following lipoproteins is produced via the exogenous lipoprotein pathway?
**(C) Chylomicrons**

14. **D**
De novo fatty acid synthesis usually signifies which of the following?
**(D) An excess of energy yielding substrates**

15. **B**
Which of the following enzymes is responsible for the initial step in β-oxidation of fatty acids?
**(B) Carnitine palmitoyltransferase I**

10
16. **C**
Which of the following is not produced during one round of β-oxidation for a saturated fatty acid?
**(C) Glycerol**

17. **D**
Iron–sulfur clusters [Fe–S] are the key prosthetic group that carry electrons in all of the below except:
**(D) Cytochrome c oxidase**

Here are the selected answers for each question:

18. **A**
Which of the following is the right combination of energy–rich molecules produced from one molecule
of Acetyl-CoA when metabolized by the citric acid cycle?
**(A) 3 NADH + 1 FADH2 + 1 GTP**

19. **B**
What is the primary function of liver glycogen?
**(B) Maintain blood glucose levels, especially during fasting**

20. **A**
What is the importance of glucose phosphorylation at the start of glycolysis?
**(A) To trap glucose inside the cell**

21. **B**
The pentose phosphate pathway (HMP shunt) primarily produces which of the following?
**(B) NADPH and ribose-5-phosphate**

22. **C**
Which ion is necessary for the activation of salivary amylase?
**(C) Chloride (Cl⁻)**

23. **C**
Glycolysis produces ATP by:
**(C) Substrate-level phosphorylation.**

24. **C**
What is the importance of fermentation to cellular metabolism?
**(C) It oxidizes NADH to NAD+ in the absence of O2**
Here are the selected answers for each question:

25. **D**
When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts
anaerobically because:
**(D) Under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by
the citric acid cycle rather than reduced to lactate.**

26. **D**
Which of the following statements is incorrect?
**(D) Under anaerobic conditions, pyruvate does not form because glycolysis does not occur.**

27. **C**

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 Which of the following is a component of lung or pulmonary surfactant found in the extracellular lipid
layer lining the pulmonary alveoli?
**(C) Phosphatidylcholine**

28. **C**
Which phospholipase hydrolyzes the fatty acid of glycerophospholipids at C1?
**(C) Phospholipase A1**

29. **B**
The beta oxidation of a 14-carbon fatty acid produces:
**(B) 7 Acetyl-CoA**

30. **B**
The deficiency of sphingomyelinase causes:
**(B) Niemann-Pick Disease**

12