Glycolysis (AQA A Level Biology): Revision Note

Aerobic respiration: glycolysis

• Glycolysis is the first stage of respiration and takes place in the cell cytoplasm

• Oxygen is not required for glycolysis, so it can be said to be an anaerobic process

  • Glycolysis occurs in both aerobic and anaerobic respiration

• Glycolysis involves the following stages:

  1. phosphorylation of glucose (6C) to glucose phosphate; this process requires 2 x ATP molecules

     • The addition of phosphate here makes glucose more reactive

  2. splitting of glucose phosphate (6C) to produce two molecules of triose phosphate (3C)

  3. oxidation of triose phosphate to pyruvate (3C)

     • Electrons and hydrogen are transferred to NAD, so 1 x NAD is reduced per molecule of triose phosphate

     • Phosphate groups are transferred to ADP in substrate-level phosphorylation, so 2 x ATP are produced per molecule of triose phosphate; a total of 4 x ATP

• The products of glycolysis include:

  • 2 x pyruvate (3C)

  • a net gain of 2 x ATP

  • 2 x reduced NAD