Outline the theoretical maximum yield of ATP per molecule of glucose, during aerobic respiration.

The oxidation of glucose to provide energy is also called cellular respiration which occurs in a series of linked, enzyme-catalysed reactions. The reactions that take place come under three main stages; glycolysis, the Krebs cycle and oxidative phosphorylation. The key product of cellular respiration is ATP. This is mainly because of the phosphoanhydride bonds (that link the phosphate groups together) as when they are hydrolysed, produce a large yield of energy. ATP acts as an immediate source of energy in living cells and so therefore is produced at a high rate as it gets used up very quickly.

The stage glycolysis takes place in the cytoplasm of cells and consists of many enzymes which help to speed up the reaction. Each glucose molecule is converted step-by-step into two molecules of pyruvate-which is a compound that consists of three carbon atoms and links gycolysis to the next reactions.

The process of glucose being broken down into two pyruvate is also called phosphorylation. The main reason why this process takes place is to prevent glucose from leaving the cell as the membrane is impermeable to sugar phosphates. Another reason is that phosphorylation makes glucose more reactive, so it is more easily converted into phosphorylated three-carbon compounds.

The products of glycolysis link to the next reaction- the Kreb cycle. In aerobic respiration, the pyruvate passes into the matrix of a mitochondrion which is where the reaction takes place. The link reaction occurs, in which pyruvate is converted into acetate and combined with a compound called coenzyme A, to form acetyl coenzyme A.

pyruvate + NAD+ + CoA → acetyl CoA + NADH + CO2