Which compound plays a pivotal role in both the first and last step of the TCA cycle? a. pyruvate b. oxaloacetate c. oxalate d. glycerol e. acetyl CoA

Option b oxaloacetate is the right one.

Explanation:

There are major eight steps in TCA cycle. Oxaloacetate plays a pivotal role in first and eight steps of cycle.

Step 1. In the first step of the citric acid cycle, acetyl CoA joins with a four-carbon molecule, oxaloacetate, releasing the CoA group and forming a six-carbon molecule called citrate.

Step 8. In the last step of the citric acid cycle, oxaloacetate-the starting four-carbon compound-is regenerated by oxidation of malate. Another molecule of NAD + is reduced to NADH in the process.