Although Other Nutrients Can Feed into the Citric Acid Cycle

Question

Although other nutrients can feed into the citric acid cycle, ________ yields energy the quickest.
A) glycogen
B) glucose
C) protein
D) fat
E) an amino acid

Accepted Answer

Glucose is the primary source of energy for the citric acid cycle, and it can be rapidly broken down into pyruvate and acetyl-CoA, which enter the cycle. Glycogen can also be broken down into glucose, but this process requires additional steps before glucose can enter the cycle. Protein and fat must be converted into intermediates that can enter the cycle, which takes more time and energy. Amino acids can enter the cycle, but this also requires additional steps and may not yield energy as quickly as glucose.