Nutritional Science & Dietetics Flashcards

Which fatty acid is classified as essential because humans cannot synthesize it?

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.

A patient has megaloblastic anemia with normal serum folate but elevated homocysteine. Which nutrient deficiency best explains this?

Answer: Vitamin B12

Vitamin B12 deficiency causes megaloblastic anemia and elevated homocysteine because it is required for methionine synthase, which converts homocysteine to methionine.

The thermic effect of food (TEF) contributes approximately what percentage of total daily energy expenditure?

Answer: 5–10%

TEF accounts for approximately 5–10% of total daily energy expenditure, representing energy used to digest, absorb, and metabolize nutrients.

Which dietary fiber fermented by gut bacteria produces the greatest amount of butyrate?

Answer: Resistant starch

Resistant starch is the primary substrate for butyrate production by colonic bacteria, making it particularly beneficial for colonocyte health.

Scurvy results from vitamin C deficiency primarily because ascorbic acid is required for which enzymatic process?

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.

A client consuming a vegan diet is most at risk for which combination of nutrient deficiencies?

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.

What is the primary role of intrinsic factor in nutrition?

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.