Question

How does the cell replenish oxaloacetate, α-ketoglutarate, and succinyl-CoA?

Short answer

The cell replenishes oxaloacetate, α-ketoglutarate, and succinyl-CoA by carboxylation of pyruvate, glutamate from glutamate dehydrogenase, and beta-oxidation of fatty acids.

Step-by-step solution

Step 1: Oxaloacetate,  ketoglutarate, and succinyl-CoA

The intermediates generated throughout the citric acid cycle are oxaloacetate, $\alpha$-ketoglutarate, and succinyl-CoA.

The term "replenishment" refers to the act of replenishing or recharging something.

Explain the way these components are generated

The following methods are used to replace oxaloacetate, $\alpha$- ketoglutarate, and succinyl-CoA:

- The carboxylation of pyruvate can restore oxaloacetate. The enzyme pyruvate carboxylase catalyzes this reaction. In the presence of the enzyme aspartate transaminase, aspartate can also replace oxaloacetate through a transamination event.

-$\alpha$--ketoglutarate can be supplied by the enzyme glutamate dehydrogenase transamination glutamate.

- In the presence of the enzyme methylmlonyl-CoA mutase, succinyl CoA can be supplied by beta-oxidation of fatty acids.