In human bioenergetics, which fuel source is generally the most effective (highest ATP yield per carbon) for producing ATP via aerobic metabolism?

• A. Glycogen
• B. Glucose
• C. Fatty acids (e.g., palmitate)
• D. Ethanol

Answer: (C)

Verified step by step guidance

1. Understand that the question asks which fuel source yields the highest amount of ATP per carbon atom during aerobic metabolism in humans.
2. Recall that aerobic metabolism involves complete oxidation of the fuel source to CO2 and H2O, producing ATP mainly through the electron transport chain and oxidative phosphorylation.
3. Compare the ATP yield per carbon for carbohydrates (like glucose and glycogen) versus fatty acids. Carbohydrates typically yield about 30-32 ATP per glucose molecule (6 carbons), while fatty acids yield more ATP per carbon due to their highly reduced state.
4. Recognize that fatty acids, such as palmitate (a 16-carbon saturated fatty acid), undergo beta-oxidation producing acetyl-CoA units, NADH, and FADH2, which feed into the citric acid cycle and electron transport chain, resulting in a higher ATP yield per carbon compared to carbohydrates.
5. Conclude that because fatty acids are more reduced and yield more electron carriers per carbon, they are generally the most effective fuel source for ATP production per carbon atom in aerobic metabolism.