Glycolysis (sugar splitting) is the first stage of both aerobic and anaerobic respiration. It takes place in the cytoplasm and converts one molecule of glucose (6C) into two molecules of pyruvate (3C).
1. Phosphorylation: two ATP molecules are hydrolysed and their phosphate groups are added to glucose, forming hexose bisphosphate. This makes the sugar more reactive.
2. Splitting: hexose bisphosphate splits into two 3-carbon molecules of triose phosphate.
3. Oxidation: hydrogen is removed from each triose phosphate by a dehydrogenase and accepted by NAD, forming reduced NAD.
4. ATP formation: each triose phosphate is converted to pyruvate, producing 2 ATP by substrate-level phosphorylation (a phosphate is transferred directly from an intermediate to ADP).Totals per glucose:
• ATP made: 2 × 2 = 4; ATP used: 2; net gain 2 ATP
• 2 reduced NAD
• 2 pyruvateGlycolysis needs no oxygen, but it does need a supply of NAD. If reduced NAD cannot be reoxidised, glycolysis stops. With oxygen, reduced NAD passes its hydrogen to the electron transport chain; without it, NAD is regenerated by converting pyruvate to lactate or ethanol.
1. Phosphorylation: two ATP molecules are hydrolysed and their phosphate groups are added to glucose, forming hexose bisphosphate. This makes the sugar more reactive.
2. Splitting: hexose bisphosphate splits into two 3-carbon molecules of triose phosphate.
3. Oxidation: hydrogen is removed from each triose phosphate by a dehydrogenase and accepted by NAD, forming reduced NAD.
4. ATP formation: each triose phosphate is converted to pyruvate, producing 2 ATP by substrate-level phosphorylation (a phosphate is transferred directly from an intermediate to ADP).Totals per glucose:
• ATP made: 2 × 2 = 4; ATP used: 2; net gain 2 ATP
• 2 reduced NAD
• 2 pyruvateGlycolysis needs no oxygen, but it does need a supply of NAD. If reduced NAD cannot be reoxidised, glycolysis stops. With oxygen, reduced NAD passes its hydrogen to the electron transport chain; without it, NAD is regenerated by converting pyruvate to lactate or ethanol.