Question

Which of the compounds in the citric acid cycle are high-energy compounds or transfer chemical energy?

1) Citrate
2) Isocitrate
3) α-Ketoglutarate
4) Succinyl-CoA
5) Succinate
6) Fumarate
7) Malate
8) Oxaloacetate

Answer 1

The high-energy compounds in the citric acid cycle that transfer chemical energy are Succinyl-CoA, NADH, and FADH2. Succinyl-CoA is involved in forming GTP, while both NADH and FADH2 act as electron carriers to generate ATP during oxidative phosphorylation.

Step-by-step explanation:

The compounds in the citric acid cycle that are considered high-energy compounds or that transfer chemical energy are:

Succinyl-CoA: It has a high-energy thioester bond whose hydrolysis drives the synthesis of guanosine triphosphate (GTP).

NADH and FADH2: Produced during the oxidation reactions and are electron carriers that enter the oxidative phosphorylation system to generate ATP.

The cycle begins with the production of citrate from acetyl CoA and oxaloacetate. Then, citrate undergoes several reactions, and energy is harnessed to reduce NAD+ to NADH and FAD to FADH2, as well as to phosphorylate GDP to GTP, which can transfer its energy to form ATP. The cycle generates three NADH, one FADH2, and one ATP (or GTP) per turn from each acetyl CoA molecule. Not all intermediates are involved directly in the energy transfer; rather, they serve as substrates that are transformed along the cycle.