NTP Human Nutrition Fundamentals 3 — Questions and Answers
Question 1: Which lipoprotein is primarily responsible for transporting cholesterol from the liver to peripheral tissues?
- HDL
- VLDL
- LDL (Correct answer)
- Chylomicrons
Correct answer: LDL
LDL (low-density lipoprotein), formed from VLDL after triglyceride removal, delivers cholesterol to peripheral cells via LDL receptor-mediated endocytosis.
Question 2: What is the primary role of intrinsic factor in nutrition?
- Activating vitamin D in the kidney
- Binding vitamin B12 to enable ileal absorption (Correct answer)
- Transporting iron across the intestinal mucosa
- Converting beta-carotene to retinol
Correct answer: Binding vitamin B12 to enable ileal absorption
Intrinsic factor, secreted by gastric parietal cells, binds cobalamin and the complex is absorbed via specific receptors in the terminal ileum.
Question 3: Secretin, released by S-cells of the duodenum, primarily stimulates:
- Gastric acid secretion
- Bile salt synthesis in the liver
- Pancreatic bicarbonate secretion (Correct answer)
- Cholecystokinin release
Correct answer: Pancreatic bicarbonate secretion
Secretin is triggered by acidic chyme entering the duodenum and signals the pancreas to release bicarbonate-rich juice to neutralize the acid.
Question 4: Which amino acid is considered conditionally essential and is the primary fuel source for enterocytes?
- Arginine
- Glutamine (Correct answer)
- Taurine
- Cysteine
Correct answer: Glutamine
Glutamine is the preferred metabolic fuel for rapidly dividing intestinal epithelial cells and becomes essential during physiological stress.
Question 5: The process of converting excess glucose to fatty acids for storage is called:
- Glycogenolysis
- Gluconeogenesis
- De novo lipogenesis (Correct answer)
- Lipolysis
Correct answer: De novo lipogenesis
De novo lipogenesis occurs primarily in the liver when glycogen stores are full, converting acetyl-CoA from excess carbohydrate into palmitate.
Question 6: Which form of vitamin D is the major circulating storage form measured in serum tests?
- Cholecalciferol (D3)
- Ergocalciferol (D2)
- 25-hydroxyvitamin D (calcidiol) (Correct answer)
- 1,25-dihydroxyvitamin D (calcitriol)
Correct answer: 25-hydroxyvitamin D (calcidiol)
25-hydroxyvitamin D (25-OHD) is the hepatic storage form with a half-life of ~3 weeks, making it the best clinical marker of vitamin D status.
Question 7: Short-chain fatty acids (SCFAs) such as butyrate, propionate, and acetate are produced primarily by:
- Pancreatic lipase activity on dietary fat
- Hepatic oxidation of medium-chain triglycerides
- Colonic microbial fermentation of dietary fiber (Correct answer)
- Beta-oxidation in muscle mitochondria
Correct answer: Colonic microbial fermentation of dietary fiber
Gut microbiota ferment soluble fiber in the colon to produce SCFAs, with butyrate serving as the primary fuel for colonocytes.
NTP Human Nutrition Fundamentals 3
Which lipoprotein is primarily responsible for transporting cholesterol from the liver to peripheral tissues?