Answer: Glycolysis is the first step of respiration in which one molecule of glucose is broken down in the cytoplasm into two molecules of pyruvic acid with the release of 2 ATP.
- It takes place in the cytoplasm and does not need oxygen.
- Glucose (6 carbon) is first phosphorylated by ATP and then split into two molecules of a 3-carbon compound (glyceraldehyde-3-phosphate).
- These are oxidised and rearranged to give two molecules of pyruvic acid (3 carbon each).
- In the process 4 ATP are formed and 2 ATP are used, so there is a net gain of 2 ATP; 2 NADH2 are also formed.
- The pyruvic acid then enters the mitochondrion, where it is converted into acetyl CoA and enters the Kreb’s cycle in aerobic respiration, or is converted into lactic acid or ethanol in anaerobic respiration.