Glycolysis

During glycolysis, glucose molecules (six-carbon molecules) are split into two pyruvates (three-carbon molecules) during a sequence of enzyme-controlled reactions. This occurs in both aerobic and anaerobic respiration.

Phosphorylation

Duringphosphorylationglucose is converted into glucose 6-phosphate using energy and phosphate groups from ATP. This is converted to fructose 1,6-diphosphate, again using ATP as a source of energy and phosphate groups. ATP is hydrolysed to ADP + phosphoric acid (Pi).

tose 1, 6-diphosphate breaks down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.

these three-carbon molecules are phosphorylated further, forming diphosphates. This reaction requires phosphoric acid and energy gained from the reduction of NAD+(oxidised form of nicotinamide adenine dinucleotide) to NADH (reduced form1,3-diphosphate molecules are dephosphorylated to form glycerate 3-phosphate molecules (a hydrolysis reaction). The energy released and the phosphate group that splits out are used to make more ATP from ADP.

to a pyruvate molecule. Again, the energy released and the phosphate group that splits out are used to make more ATP from ADP.

The link reaction

This links glycolysis to the Krebs Cycle (sometimes called the citric acid cycle). Pyruvate molecules aredecarboxylated(they lose a molecule of carbon dioxide) in the mitochondria. Pyruvate molecules are oxidized and converted to acetylcoenzyme A, usually abbreviated to acetyl CoA.

2CH3COCOO-+ 2NAD++ 2H2O --->2CH3COO-+ 2NADH + 2H++ 2CO2

The oxidised form of nicotinamide adenine dinucleotide, NAD+, is reduced to its reduced from NADH.