Ever wondered how respiration occurs within a cell?

This is an in-depth look into the process of cellular respiration in mammals. This process occurs in three stages:

1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain (Oxidative phosphorylation)

Process of glycolysis:
This is the first process of respiration and occurs in the cytoplasm of the cell.
The hexose ( 6 carbon) sugar glucose undergoes phosphorilation by two ATP molecules (Adenosine triose phosphate) This is then broken down to form glyceraldehyde 3- phosphate (two triose molecules)

Glyceraldehyde 3-phosphate is converted into pyruvate through a series of enzyme controlled reactions. During the process of conversion two NADH molecules are made.

During glycolysis two ATP molecules are made. Under anaerobic conditions a glucose molecule will only undergo glycolysis. However the pyruvate will be converted to lactic acid which causes cramps.

Krebs Cycle:
The pyruvate enters the mitochondrial matrix of mitochondria via the malate shuttle present in the membrane of the mitochondria. The pyruvate combines with acetyl co-enzymeA (CoA) to form citrate (6 carbon.) For one pyruvate molecule 2 CO2 molecules, 3 NADH and 1 FAD molecule are made.

Electron Transport Chain:
The FADH and NADH molecules move to the cristae of the mitochondria where the electron transport chain is located. These reduced co-enzymes produce Hydrogen Ions which go into the electron transport chain. The proteins within the electron transport chain transport the hydrogen ions across the inner mitochondrial membrane into the inter membranel space.

The oxygen within the mitochondrial membrane acts as a final acceptor of hydrogen to a water molecule. The accumulated hydrogen ions in the inter membranel space move through ATP synthase synthesises ATP molecules.

In total one glucose molecule causes 36 ATP molecules to be produced. These ATP molecules provide the energy for the processes within the cell.