How many carbon atoms enter the Krebs cycle per molecule of Acetyl CoA?

Acetyl CoA is a critical molecule that initiates the Krebs cycle, also known as the citric acid cycle. Each molecule of Acetyl CoA contains two carbon atoms. When Acetyl CoA enters the Krebs cycle, it combines with a four-carbon molecule called oxaloacetate to form citric acid (or citrate), which is a six-carbon compound.

Therefore, the entry of a single Acetyl CoA leads to the addition of its two carbon atoms, which are then incorporated into the cycle's metabolic reactions. Later in the cycle, these carbon atoms are eventually released as carbon dioxide during the various reactions of the Krebs cycle, but the key point is that two carbon atoms from one Acetyl CoA are what start the cycle.

This understanding is fundamental in cellular respiration, as the Krebs cycle plays a vital role in producing energy carriers such as NADH and FADH2, which are essential for the electron transport chain and ATP production.