IB DP Biology: HL复习笔记8.2.3 Glycolysis

• Glycolysis is the first stage of respiration
• It takes place in the cytoplasm of the cell and involves:
  • Trapping glucose in the cell by phosphorylating the molecule
  • Splitting the glucose molecule in two
• It results in the production of
  • Two pyruvate (3 carbon/3C) molecules
  • Net gain two ATP (Four ATP are produced in total but two are used during the reactions of glycolysis)
  • Two reduced NAD

Steps of glycolysis

• Phosphorylation: glucose (6C) is activated by phosphorylation from two ATP to form fructose-1,6-bisphosphate (6C)
  • This makes the 6C molecule less stable and therefore more reactive

Glucose + 2ATP → Fructose-1,6-bisphosphate

• Lysis
  • Fructose-1,6-bisphosphate (6C) splits into two molecules of triose phosphate (3C)

Fructose-1,6-bisphosphate → 2 Triose phosphate

• Oxidation:
  • Hydrogen is removed from each molecule of triose phosphate by dehydrogenase enzyme and transferred to coenzyme NAD to form two reduced NAD
  • Triose phosphate is oxidised to for another 3C molecule glycerate-3-phosphate

2 Triose phosphate →2 Glycerate-3-phosphate
4H + 2NAD → 2NADH + 2H⁺

• Dephosphorylation
  • Phosphates are transferred from the intermediate substrate molecules to form four ATP through substrate-linked phosphorylation

4P_i + 4ADP → 4ATP

• Pyruvate is produced
  • The end product of glycolysis which can be used in the next stage of respiration

2 Glycerate-3-phosphate → 2 Pyruvate

Glycolysis, the formation of two pyruvate molecules from one glucose sugar molecule