CNC Fundamentals of Nutrition Science 3 — Questions and Answers
Question 1: Which vitamin acts as a coenzyme in over 100 enzymatic reactions and is essential for amino acid metabolism, including the conversion of tryptophan to niacin?
- Vitamin B1 (Thiamin)
- Vitamin B2 (Riboflavin)
- Vitamin B6 (Pyridoxine) (Correct answer)
- Vitamin B12 (Cobalamin)
Correct answer: Vitamin B6 (Pyridoxine)
Vitamin B6 (pyridoxine) serves as a coenzyme (PLP) in transamination and decarboxylation reactions, including the conversion of tryptophan to niacin.
Question 2: Dietary fiber that is fermented by colonic bacteria to produce short-chain fatty acids (SCFAs) is classified as:
- Insoluble fiber
- Soluble fiber (Correct answer)
- Resistant starch only
- Cellulose
Correct answer: Soluble fiber
Soluble (fermentable) fiber is broken down by gut microbiota into SCFAs such as butyrate, propionate, and acetate, which support colonocyte health.
Question 3: What is the primary role of bile salts in fat digestion?
- Hydrolyze triglycerides into fatty acids
- Emulsify fat globules to increase surface area for lipase (Correct answer)
- Transport fatty acids across the intestinal membrane
- Synthesize chylomicrons in the intestinal wall
Correct answer: Emulsify fat globules to increase surface area for lipase
Bile salts emulsify dietary fats into smaller droplets, dramatically increasing the surface area available for pancreatic lipase to act upon.
Question 4: A diet very high in protein significantly increases the need for which nutrient to support nitrogen excretion and prevent urea accumulation?
- Sodium
- Potassium
- Water (Correct answer)
- Calcium
Correct answer: Water
Nitrogen from excess protein is converted to urea in the liver and excreted by the kidneys, increasing obligatory water loss and overall fluid requirements.
Question 5: Which mineral is a cofactor for the antioxidant enzyme glutathione peroxidase and is found in high concentrations in Brazil nuts?
- Zinc
- Manganese
- Selenium (Correct answer)
- Copper
Correct answer: Selenium
Selenium is incorporated into glutathione peroxidase, a key antioxidant enzyme; Brazil nuts are one of the richest dietary sources of selenium.
Question 6: The thermic effect of food (TEF) accounts for approximately what percentage of total daily energy expenditure in most individuals?
- 2–4%
- 5–10% (Correct answer)
- 15–20%
- 25–30%
Correct answer: 5–10%
TEF (diet-induced thermogenesis) typically represents 5–10% of total daily energy expenditure, with protein having the highest TEF (~20–30%) of all macronutrients.
Question 7: Which type of dietary fat has been shown to raise LDL cholesterol while also lowering HDL cholesterol, making it particularly harmful to cardiovascular health?
- Monounsaturated fat
- Omega-3 polyunsaturated fat
- Saturated fat
- Trans fat (Correct answer)
Correct answer: Trans fat
Trans fats (partially hydrogenated oils) uniquely raise LDL and lower HDL cholesterol simultaneously, producing an especially adverse lipid profile.
