Macronutrient & Micronutrient Science Flashcards

What is the role of intrinsic factor in vitamin B12 absorption, and where is it produced?

Answer: Intrinsic factor is produced by gastric parietal cells and is required for B12 absorption in the terminal ileum

Parietal cells in the stomach secrete intrinsic factor, which binds B12 and allows receptor-mediated absorption in the terminal ileum.

During ketogenesis, which organ is the primary site of ketone body synthesis?

Answer: Liver

The liver produces ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) from acetyl-CoA during states of low glucose/insulin, then exports them for peripheral use.

Which fat-soluble vitamin functions as an antioxidant by donating a hydrogen atom to neutralize lipid peroxyl radicals in cell membranes?

Answer: Vitamin E (tocopherol)

Alpha-tocopherol (vitamin E) is the principal lipid-soluble antioxidant in cell membranes, breaking chain reactions of lipid peroxidation.

What distinguishes soluble fiber from insoluble fiber in terms of its physiological effects?

Answer: Soluble fiber forms a gel in the gut, slowing glucose absorption and feeding beneficial bacteria; insoluble fiber adds bulk and speeds transit

Soluble fiber (e.g., pectin, beta-glucan) dissolves in water to form viscous gels that blunt glucose absorption and serve as prebiotics, while insoluble fiber (e.g., cellulose) increases stool bulk.

Copper deficiency can produce a clinical picture resembling which other nutrient deficiency?

Answer: Iron deficiency anemia, because copper is needed for iron mobilization and hemoglobin synthesis

Copper-dependent ceruloplasmin oxidizes Fe²⁺ to Fe³⁺ for iron loading onto transferrin; copper deficiency impairs iron mobilization, causing anemia similar to iron deficiency.

Which macronutrient has the highest thermic effect of feeding (TEF), meaning the body expends the most energy to digest and metabolize it?

Answer: Protein

Protein has a TEF of approximately 20–30% of its calories, compared to 5–10% for carbohydrate and 0–3% for fat, making it the most metabolically costly macronutrient to process.

A practitioner suspects a client has impaired fat-soluble vitamin absorption. Which underlying condition is the MOST likely cause?

Answer: Insufficient bile acid secretion due to liver or gallbladder dysfunction

Fat-soluble vitamins (A, D, E, K) require bile acids for micellarization and absorption; liver disease or cholestasis that reduces bile flow directly impairs their uptake.