Glycolysis

Glycolysis is a metabolic pathway in which each molecule of glucose is eventual broken down to pyruvate. This process occurs through much different stage which results in the end product. I will describe the four main stages which occur during glycolysis.

The first stage of glycolysis involves activating the glucose molecule before it can be broken down into two molecules. This involves the process of phosphorylation. A molecule of ATP is used to provide one phosphate group which is attached to carbon 6 of glucose to make glucose 6-phosphate. The glucose 6-phosphate is then converted into another hexose sugar known as fructose 6-phophate. Hydrolysing another molecule of ATP provides a phosphate group which is attached to carbon 1 of the hexose sugar to make fructose 1,6bisphosphate. This sugar is known activated as the energy from the hydrolyses of ATP activates the molecule.

The second stage involves splitting the activated six carbon molecule fructose-1,6-bisphosphate into two molecule of triose phosphate which have three carbons.

The next stage is an anaerobic stage which involves the use of an enzyme and coenzyme. From each molecule of triose phosphate two hydrogen atoms are removed by dehydrogenase enzymes. The two hydrogen atoms removed are each accepted by the coenzyme nicontinamide adenine dinucleotide (NAD) which becomes reduced To NADH2. During this stage there are two molecules of ATP produced. As there was two molecules of ATP used earlier there is no net change in ATP.

The final stage involves four enzyme catalysed reactions which convert the triose phosphate into pyruvate which is also a 3 carbon compound. During the process two molecules of ADP are phosphorylated to ATP through a process known as substrate level phosphorylation. Thus through he process of glycolysis there is a net overall gain of two molecules of ATP.