The citric acid cycle begins by combining
A)carbon dioxide and water to form carbonic acid.
B)pyruvic acid and acetic acid to form acetoacetic acid.
C)pyruvic acid and carbon dioxide to form lactic acid.
D)oxaloacetic acid and acetyl-CoA to form citric acid.
E)pyruvic acid and citric acid.

Question

Quizplus · Accepted Answer

The citric acid cycle, also known as the Krebs cycle or the tricarboxylic acid (TCA) cycle, begins with the combination of oxaloacetic acid (a four-carbon molecule) and acetyl-CoA (a two-carbon molecule derived from pyruvic acid) to form citric acid (a six-carbon molecule). Therefore, choice D is the correct answer.

The Citric Acid Cycle Begins by Combining