Biology – 4.1 Introduction to cellular respiration and fermentation:

Aerobic Cellular Respiration: is the process that extracts energy from food in the presence of oxygen. The energy is used to synthesize ATP from ADP and Pi. The ATP molecules are then used to supply energy directly to the cell for their energy-demanding activities.
The equation bellow shows how glucose and oxygen are used to release ATP:
C6H12O6 + 6O2  6CO2 + 6H2O ∆G = -2870 KJ/mol
Aerobic cellular respiration can be divided into four stages. Each stage involves the transfer of free energy, producing ATP in one of two ways: Substrate-level phosphorylation and oxidative phosphorylation.
Substrate-level phosphorylation: Forms ATP directly in an enzyme-catalyzed reaction through the transfer of a phosphate group from one molecule to an adenosine diphosphate (ADP) molecule.
Oxidative phosphorylation: forms ATP indirectly through a series of redox reactions involving a final electron acceptor. In aerobic respiration, oxygen is the final electron acceptor.
The stages of aerobic cellular respiration (not detailed):
1. Glycolysis: Occurs in the cytosol. Enzymes break down one molecule of glucose in a series of steps to two molecules of pyruvate. This process requires the use of 2 ATP molecules, but in return it produces four ATP, which is a net gain of 2 ATP. This process also releases two NADH+ electron carries and two water molecules.
Net product of Glycolysis:
2 ATP 2 NADH 2 Pyruvate 2 H2O 2 H+

2. Pyruvate oxidation: Occurs in the mitochondria. Each of the two molecules of pyruvate produced in Glycolysis is transported to mitochondria and is oxidized, resulting in the production of CO2, NADH and an acetyl group that is initially attached to coenzyme A (acetyl-CoA).
Net product of Pyruvate oxidation: (both