Macronutrient Science Flashcards

Which amino acid is considered conditionally essential during periods of intense physical stress or illness?

Answer: Glutamine

Glutamine becomes conditionally essential during catabolic stress because the body's demand exceeds its synthesis capacity.

The thermic effect of protein is approximately what percentage of its caloric value?

Answer: 25-30%

Protein has a thermic effect of approximately 25-30%, meaning roughly 25-30% of protein calories are burned during digestion and metabolism.

Medium-chain triglycerides (MCTs) differ from long-chain fatty acids primarily because they:

Answer: Are transported via the portal vein directly to the liver

MCTs bypass the lymphatic system and are transported directly via the portal vein to the liver, enabling rapid oxidation.

A client consumes 200g of carbohydrates per day. How many calories does this contribute?

Answer: 800 kcal

Carbohydrates provide 4 kcal per gram, so 200g × 4 = 800 kcal.

Which type of dietary fiber is most associated with lowering LDL cholesterol by binding bile acids in the gut?

Answer: Soluble viscous fiber

Soluble viscous fibers like beta-glucan and pectin form gels in the gut that trap bile acids, forcing the liver to convert more cholesterol into bile.

During gluconeogenesis, which macronutrient-derived substrate is NOT typically used to synthesize glucose?

Answer: Acetyl-CoA from fatty acid oxidation

Acetyl-CoA cannot be converted to glucose in humans because the pyruvate dehydrogenase reaction is irreversible and there is no net glucogenic pathway from pure acetyl-CoA.

The concept of 'leucine threshold' in muscle protein synthesis refers to:

Answer: The minimum leucine dose needed to maximally stimulate mTORC1 signaling

The leucine threshold is the minimum leucine dose (~2-3g per meal) required to fully activate mTORC1 and maximize the muscle protein synthesis response.