Beginning of Essay
begins with glucose. Glucose is the primary fuel used in glycolysis, the first stage of . This molecule is found in the gel-like substance called cytoplasm that fills the cell. In glycolysis, glucose undergoes phosphorylation by ATP. The ATP is converted back ....

Middle of Essay
.... molecule is transformed into a two-carbon compound called an acetyl group. The two acetyl groups combine with a molecule of coenzyme A each to form two acetyl coenzyme A molecules. These molecules are processed in a complex pathway called the Krebs cycle. As the Krebs cycle progresses through both pyruvic acid molecules, six molecules of NADH, two molecules of ATP, and additional carbon dioxide are all formed. FAD picks up a hydrogen atom from each pyruvic acid molecule, and a total of 2 FAD2 are formed. NADH and FAD2 transport their hydrogen atoms and electrons to the electron transport chain. The electrons are passed down the chain of attr ....