Clinical Nutritionist CCN Macronutrients and Metabolism 2 — Questions and Answers
Question 1: Which lipoprotein is responsible for transporting cholesterol from peripheral tissues back to the liver?
- HDL (Correct answer)
- LDL
- VLDL
- Chylomicrons
Correct answer: HDL
High-density lipoprotein (HDL) mediates reverse cholesterol transport, carrying excess cholesterol from tissues to the liver for excretion.
Question 2: What is the primary fuel source for the brain under normal fed conditions?
- Glucose (Correct answer)
- Fatty acids
- Ketone bodies
- Amino acids
Correct answer: Glucose
The brain relies almost exclusively on glucose for energy under normal conditions because fatty acids cannot cross the blood-brain barrier efficiently.
Question 3: During beta-oxidation of a 16-carbon saturated fatty acid, how many acetyl-CoA molecules are produced?
- 8 (Correct answer)
- 4
- 16
- 6
Correct answer: 8
Each round of beta-oxidation cleaves a 2-carbon acetyl-CoA unit, so a 16-carbon fatty acid yields 8 acetyl-CoA molecules.
Question 4: Which enzyme is the rate-limiting step of fatty acid synthesis?
- Acetyl-CoA carboxylase (Correct answer)
- Fatty acid synthase
- Malonyl-CoA decarboxylase
- Citrate lyase
Correct answer: Acetyl-CoA carboxylase
Acetyl-CoA carboxylase catalyzes the carboxylation of acetyl-CoA to malonyl-CoA, the committed and rate-limiting step in fatty acid synthesis.
Question 5: What is the thermic effect of food (TEF) for dietary protein compared to carbohydrates and fat?
- 20-30% for protein vs 5-10% for carbs and 0-3% for fat (Correct answer)
- 5% for all macronutrients equally
- 10% for protein vs 15% for carbs and 8% for fat
- 30% for fat vs 10% for protein and 5% for carbs
Correct answer: 20-30% for protein vs 5-10% for carbs and 0-3% for fat
Protein has the highest thermic effect (20-30%), meaning it requires the most energy to digest, absorb, and metabolize compared to other macronutrients.
Question 6: Which metabolic state is characterized by elevated blood ketone bodies, typically seen during prolonged fasting or very low carbohydrate intake?
- Ketosis (Correct answer)
- Acidosis
- Gluconeogenesis
- Glycogenolysis
Correct answer: Ketosis
Ketosis occurs when the liver produces ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) from acetyl-CoA during states of low carbohydrate availability.
Clinical Nutritionist CCN Macronutrients and Metabolism 2
Which lipoprotein is responsible for transporting cholesterol from peripheral tissues back to the liver?