What is the First Reactant in the Citric Acid Cycle

Question

What is the first reactant in the citric acid cycle?
A) pyruvic acid (C₃H₃O₃)
B) glucose (C₆H₁₂O₆)
C) carbon dioxide (CO₂)
D) oxalaoacetate (OAA)

Accepted Answer

The first reactant in the citric acid cycle is oxaloacetate (OAA). This molecule combines with acetyl-CoA to form citrate, which begins the cycle. Pyruvic acid and glucose are converted to acetyl-CoA before entering the cycle, and carbon dioxide is produced as a byproduct of the cycle.