Medical Biochemistry II PAPER A (MBMB 2200) – 10 MCQs | Kenya MBChB

10 Year 2: Clinical Biochemistry exam questions on Medical Biochemistry II PAPER A (MBMB 2200) for medical students. Includes MCQs, answers, explanations and wr

This MCQ set contains 10 questions on Medical Biochemistry II PAPER A (MBMB 2200) in the Year 2: Clinical Biochemistry unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.

Q1: The molecule that serves as the major source of readily available fuel for neurons and blood cells is

  1. A. Fat
  2. B. Glucose
  3. C. Acetyl CoA
  4. D. Cellulose
  5. E. Glycogen

Correct answer: B – Glucose

Glucose is the primary energy source for neurons and red blood cells. Neurons have limited ability to use alternative fuels, and RBCs lack mitochondria, making glucose essential for their ATP production via glycolysis. ---

Q2: Ammonia is an effective and important urinary buffer for which of the following reasons

  1. A. Its production in the kidney decreases during chronic acidosis
  2. B. The walls of the renal tubules are impermeable to NH3
  3. C. The walls of the renal tubules are impermeable to NH4+
  4. D. Its acid base reaction has a low pKa
  5. E. None of the above

Correct answer: C – The walls of the renal tubules are impermeable to NH4+

NH3 diffuses into tubular fluid where it combines with H+ to form NH4+. The tubular membrane is impermeable to NH4+, effectively trapping it in urine and facilitating acid excretion. ---

Q3: Which of the choices below is not a fate of carbohydrate taken into the body

  1. A. ATP production
  2. B. Lipogenesis
  3. C. Amino acid synthesis
  4. D. Conversion to a nucleic acid
  5. E. Glycogenesis

Correct answer: D – Conversion to a nucleic acid

While carbohydrates can provide ribose for nucleic acid synthesis, they are not directly converted to nucleic acids. The other options are all direct metabolic fates of carbohydrates. ---

Q4: The amount of potassium excreted by the kidney will decrease if

  1. A. Distal tubular flow increases
  2. B. Circulating aldosterone levels increase
  3. C. Dietary intake of potassium increases
  4. D. Na+ reabsorption by the distal nephron decreases
  5. E. The excretion of organic ions increases

Correct answer: B – Circulating aldosterone levels increase

Aldosterone promotes Na+ reabsorption and K+ secretion in the distal nephron. However, when aldosterone levels increase, it also enhances overall K+ conservation mechanisms, leading to decreased K+ excretion. ---

Q5: An increase in the concentration of plasma potassium causes increases in

  1. A. Release of renin
  2. B. Secretion of aldosterone
  3. C. Secretion of ADH
  4. D. Release of natriuretic hormone
  5. E. Production of angiotensin II

Correct answer: B – Secretion of aldosterone

Hyperkalemia directly stimulates aldosterone secretion from the adrenal cortex, which promotes K+ excretion in the distal nephron to restore K+ homeostasis. ---

Q6: Glomerular filtration rate would be increased by

  1. A. Constriction of the afferent arteriole
  2. B. A decrease in afferent arteriolar pressure
  3. C. Compression of the renal capsule
  4. D. A decrease in the concentration of plasma protein
  5. E. A decrease in renal blood flow

Correct answer: D – A decrease in the concentration of plasma protein

Decreased plasma protein concentration reduces oncotic pressure, decreasing the force opposing filtration and thereby increasing GFR. ---

Q7: The greatest amount of hydrogen ion secreted by the proximal tubule is associated with

  1. A. Excretion of potassium ion
  2. B. Excretion of hydrogen ion
  3. C. Reabsorption of calcium ion
  4. D. Reabsorption of bicarbonate ion
  5. E. Reabsorption of phosphate ion

Correct answer: D – Reabsorption of bicarbonate ion

About 80-90% of filtered bicarbonate is reabsorbed in the proximal tubule via H+ secretion, making bicarbonate reabsorption the major mechanism of proximal H+ secretion. ---

Q8: Urinalysis is comprised of all of the following except

  1. A. Macroscopic analysis
  2. B. Dipstick testing
  3. C. Microscopic analysis
  4. D. Chemical analysis
  5. E. All of the above

Correct answer: E – All of the above

This is a trick question. Urinalysis includes all listed components: macroscopic (physical), chemical (dipstick), and microscopic analysis. ---

Q9: Glycogen is formed in the liver during the

  1. A. Pre-absorptive state
  2. B. Post absorptive state
  3. C. Absorptive state
  4. D. Starvation period
  5. E. Period when the metabolic rate is lowest

Correct answer: C – Absorptive state

Glycogenesis (glycogen synthesis) occurs during the absorptive state when glucose is abundant after eating, allowing storage of excess glucose as glycogen. ---

Q10: Which of the following is a normal consequence of the activation of the heat-promoting center

  1. A. Release of epinephrine
  2. B. Sympathetic sweat gland activation
  3. C. Increase in ADH production
  4. D. Vasodilation of cutaneous blood vessels
  5. E. Vasoconstriction of cutaneous blood vessels

Correct answer: E – Vasoconstriction of cutaneous blood vessels

Heat-promoting center activation causes vasoconstriction of skin blood vessels to conserve body heat by reducing heat loss

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