Fat Burning Fundamentals and Core Concepts 2 — Questions and Answers
Question 1: Which hormone is primarily responsible for signaling fat cells to release stored fatty acids into the bloodstream?
- Insulin
- Glucagon
- Epinephrine (Correct answer)
- Cortisol
Correct answer: Epinephrine
Epinephrine (adrenaline) binds to beta-adrenergic receptors on fat cells and activates hormone-sensitive lipase to release fatty acids.
Question 2: What is the term for the process by which fatty acids are converted to acetyl-CoA inside the mitochondria?
- Lipogenesis
- Beta-oxidation (Correct answer)
- Gluconeogenesis
- Lipolysis
Correct answer: Beta-oxidation
Beta-oxidation is the mitochondrial process that sequentially removes two-carbon units from fatty acid chains, producing acetyl-CoA, NADH, and FADH2.
Question 3: At what approximate exercise intensity (% of VO2 max) does the body burn the greatest absolute amount of fat per minute?
- 25–35%
- 45–65% (Correct answer)
- 70–80%
- 85–95%
Correct answer: 45–65%
Fat oxidation peaks at moderate intensities around 45–65% of VO2 max, often called the 'fat-burning zone,' before carbohydrate use overtakes it at higher intensities.
Question 4: Which molecule must fat be converted into before it can enter the Krebs cycle for energy production?
- Pyruvate
- Lactate
- Acetyl-CoA (Correct answer)
- ATP
Correct answer: Acetyl-CoA
Beta-oxidation converts fatty acids into acetyl-CoA, the two-carbon molecule that feeds directly into the citric acid (Krebs) cycle.
Question 5: Which enzyme, found in fat cells, is specifically activated during lipolysis to break down stored triglycerides?
- Lipoprotein lipase
- Hormone-sensitive lipase (Correct answer)
- Pancreatic lipase
- Fatty acid synthase
Correct answer: Hormone-sensitive lipase
Hormone-sensitive lipase (HSL) is activated by catecholamines and inhibited by insulin, making it the key regulatory enzyme for mobilizing stored fat.
Question 6: What is the primary role of carnitine in fat metabolism?
- It digests dietary fat in the small intestine
- It transports long-chain fatty acids across the inner mitochondrial membrane (Correct answer)
- It converts glucose to fatty acids
- It stores fatty acids as triglycerides
Correct answer: It transports long-chain fatty acids across the inner mitochondrial membrane
Carnitine forms acylcarnitine conjugates that shuttle long-chain fatty acids across the inner mitochondrial membrane so beta-oxidation can occur.
Question 7: Which of the following dietary macronutrients has the highest thermic effect of food (TEF), meaning the body burns the most calories digesting it?
- Fat
- Carbohydrate
- Protein (Correct answer)
- Fiber
Correct answer: Protein
Protein has a TEF of approximately 20–30%, meaning the body expends 20–30 calories for every 100 calories of protein consumed.
Fat Burning Fundamentals and Core Concepts 2
Which hormone is primarily responsible for signaling fat cells to release stored fatty acids into the bloodstream?