Medical Biochemistry II PAPER A (MBMB 2200) | MCQ Quiz | OmpathStudy Kenya

Question 1

The probability that disease is present when a test result falls outside reference interval is called the test's

Accepted Answer

Positive predictive value — Positive predictive value (PPV) represents the probability that a patient actually has the disease when the test result is positive (outside reference interval). It depends on both test characteristics and disease prevalence. ---

Question 2

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

Accepted Answer

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. ---

Question 3

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

Accepted Answer

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. ---

Question 4

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

Accepted Answer

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. ---

Question 5

The amount of potassium excreted by the kidney will decrease if

Accepted Answer

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. ---

Question 6

Dietary fats are important because they

Accepted Answer

Help the body absorb fat-soluble vitamins — Dietary fats are essential for absorption of fat-soluble vitamins (A, D, E, K) in the intestine. These vitamins require lipid micelles for proper absorption. ---

Question 7

An increase in the concentration of plasma potassium causes increases in

Accepted Answer

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

Question 8

When proteins undergo deamination, the waste substance found in the urine is mostly

Accepted Answer

Urea — Protein deamination produces ammonia, which is converted to urea in the liver via the urea cycle. Urea is the major nitrogenous waste product excreted in human urine. ---

Question 9

Glomerular filtration rate would be increased by

Accepted Answer

A decrease in the concentration of plasma protein — Decreased plasma protein concentration reduces oncotic pressure, decreasing the force opposing filtration and thereby increasing GFR. ---

Question 10

Lipogenesis occurs when

Accepted Answer

Cellular ATP and glucose levels are high — Lipogenesis (fat synthesis) occurs during fed state when energy (ATP) and substrate (glucose) are abundant, allowing conversion of excess carbohydrates to fat for storage. ---

Question 11

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

Accepted Answer

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. ---

Question 12

Oxidative deamination takes place in the

Accepted Answer

Liver — The liver is the primary site of oxidative deamination where amino acids are deaminated to produce ammonia, which is then converted to urea. ---

Question 13

Urinalysis is comprised of all of the following except

Accepted Answer

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

Question 14

Glycogen is formed in the liver during the

Accepted Answer

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

Question 15

Urine that is not tested immediately or refrigerated before testing will give inaccurate results due to all of the following except

Accepted Answer

Increased acidity — Urine typically becomes more alkaline (not acidic) upon standing due to bacterial conversion of urea to ammonia. The other changes all occur with delayed testing. ---

Question 16

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

Accepted Answer

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

Medical Biochemistry II PAPER A (MBMB 2200) | MCQ Quiz | OmpathStudy Kenya

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