The compound that enters the Krebs cycle is acetyl-CoA. It is made from the last compound of glycolysis, pyruvate.

Here's how it works:

1. Glycolysis: Glucose is broken down into two pyruvate molecules.

2. Pyruvate Oxidation: Each pyruvate molecule is converted into acetyl-CoA. This happens in the mitochondrial matrix and involves the removal of a carbon dioxide molecule and the addition of coenzyme A.

3. Krebs Cycle: Acetyl-CoA enters the Krebs cycle, where it is further oxidized to generate ATP, NADH, and FADH2.

So, the cycle is completed when pyruvate, the product of glycolysis, is converted into acetyl-CoA, which then fuels the Krebs cycle.