CDN Nutritional Science & Dietetics 2 — Questions and Answers
Question 1: Which fatty acid is classified as essential because humans cannot synthesize it?
- Oleic acid (18:1n-9)
- Linoleic acid (18:2n-6) (Correct answer)
- Palmitic acid (16:0)
- Stearic acid (18:0)
Correct answer: Linoleic acid (18:2n-6)
Linoleic acid is an essential omega-6 fatty acid that must be obtained from the diet because humans lack the delta-12 desaturase enzyme needed to synthesize it.
Question 2: A patient has megaloblastic anemia with normal serum folate but elevated homocysteine. Which nutrient deficiency best explains this?
- Iron
- Vitamin B12 (Correct answer)
- Vitamin B6
- Copper
Correct answer: Vitamin B12
Vitamin B12 deficiency causes megaloblastic anemia and elevated homocysteine because it is required for methionine synthase, which converts homocysteine to methionine.
Question 3: The thermic effect of food (TEF) contributes approximately what percentage of total daily energy expenditure?
- 2–3%
- 5–10% (Correct answer)
- 15–20%
- 25–30%
Correct answer: 5–10%
TEF accounts for approximately 5–10% of total daily energy expenditure, representing energy used to digest, absorb, and metabolize nutrients.
Question 4: Which dietary fiber fermented by gut bacteria produces the greatest amount of butyrate?
- Cellulose
- Psyllium husk
- Resistant starch (Correct answer)
- Pectin
Correct answer: Resistant starch
Resistant starch is the primary substrate for butyrate production by colonic bacteria, making it particularly beneficial for colonocyte health.
Question 5: Scurvy results from vitamin C deficiency primarily because ascorbic acid is required for which enzymatic process?
- Heme iron absorption
- Prolyl hydroxylase activity in collagen synthesis (Correct answer)
- Phenylalanine hydroxylation
- Electron transport chain function
Correct answer: Prolyl hydroxylase activity in collagen synthesis
Vitamin C acts as a cofactor for prolyl and lysyl hydroxylases, enzymes essential for hydroxylating collagen precursors, which is necessary for proper cross-linking and structural integrity.
Question 6: A client consuming a vegan diet is most at risk for which combination of nutrient deficiencies?
- Vitamins A and K2
- Vitamins B12, D, calcium, and zinc (Correct answer)
- Vitamins C and E
- Iron and potassium
Correct answer: Vitamins B12, D, calcium, and zinc
Vegan diets commonly lack vitamin B12 (found only in animal products), vitamin D, calcium, and zinc due to limited bioavailability from plant sources.
Question 7: What is the primary role of intrinsic factor in nutrition?
- Facilitating iron absorption in the duodenum
- Binding vitamin B12 for absorption in the terminal ileum (Correct answer)
- Activating vitamin D in the kidney
- Transporting folate across the intestinal epithelium
Correct answer: Binding vitamin B12 for absorption in the terminal ileum
Intrinsic factor, secreted by gastric parietal cells, binds vitamin B12 and the complex is absorbed by specific receptors in the terminal ileum.
CDN Nutritional Science & Dietetics 2
Which fatty acid is classified as essential because humans cannot synthesize it?