AFAA Personal Trainer Certification Practice Exam

Which component of the Krebs cycle is formed from carbohydrates?

1. Carbon dioxide

2. Acetyl CoA

3. Fatty acids

4. Lactic acid

The correct answer is: Acetyl CoA

Acetyl CoA is formed from carbohydrates during the process of glycolysis, which is the breakdown of glucose. When carbohydrates are consumed and metabolized, they go through glycolysis, where glucose is split into two molecules of pyruvate. This pyruvate can then enter the mitochondria, where each pyruvate molecule undergoes a conversion process involving the enzyme pyruvate dehydrogenase, resulting in the formation of Acetyl CoA. Acetyl CoA serves as the entry point into the Krebs cycle (also known as the citric acid cycle or TCA cycle). It combines with oxaloacetate to form citric acid and initiates a series of reactions that produce energy in the form of ATP, NADH, and FADH2, as well as releasing carbon dioxide as a byproduct. This highlights the significant role of Acetyl CoA as a key player in cellular respiration, particularly in energy metabolism derived from carbohydrates. Other options, while related to metabolic processes, do not directly stem from carbohydrates in the context of the Krebs cycle formation. Carbon dioxide is a byproduct of the Krebs cycle itself, fatty acids are products of lipid metabolism, and lactic acid is produced during anaer