AP BIOLOGY

Detailed explanation-1: -The Krebs cycle starts with pyruvic acid from glycolysis. Each small circle in the diagram represents one carbon atom. For example, citric acid is a six carbon molecule, and OAA (oxaloacetate) is a four carbon molecule.

Detailed explanation-2: -The citric acid cycle is called a cycle because the starting molecule, oxaloacetate (which has 4 carbons), is regenerated at the end of the cycle.

Detailed explanation-3: -Breakdown of Pyruvate In order for pyruvate, the product of glycolysis, to enter the next pathway, it must undergo several changes to become acetyl Coenzyme A (acetyl CoA). Acetyl CoA is a molecule that is further converted to oxaloacetate, which enters the citric acid cycle (Krebs cycle).

Detailed explanation-4: -Pyruvic acid is the formed product (end) of glycolysis, a process that breaks down glucose (a 6-C molecule) into two molecules of pyruvate (a 3-C molecule) and simultaneously yields adenosine triphosphate (ATP), which powers cellular function.

Detailed explanation-5: -Glycolysis, the first step of cellular respiration, occurs in the cytoplasm of your cells. During this process, a glucose molecule is broken down into two molecules of pyruvate (pyruvic acid).