outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules (3C), which are then further oxidised to pyruvate (3C), with the production of ATP and reduced NAD

Glycolysis – Energy Yields and Key Reactions

1. Phosphorylation of Glucose

Glucose is phosphorylated twice, consuming two ATP molecules before the molecule is split.

1. Hexokinase: \$C6H{12}O6 + ATP \rightarrow C6H{12}O7P + ADP\$
2. Phosphoglucose isomerase: \$C6H{12}O7P \rightarrow C6H{12}O7P\$ (isomerisation to fructose‑6‑phosphate)
3. Phosphofructokinase‑1: \$C6H{12}O7P + ATP \rightarrow C6H{12}O9P + ADP\$

2. Cleavage of Fructose 1,6‑bisphosphate

Fructose 1,6‑bisphosphate is split into two triose phosphates.

• Enzyme: aldolase
• Products: glyceraldehyde‑3‑phosphate (G3P) and dihydroxyacetone phosphate (DHAP)
• DHAP is converted to G3P by triose phosphate isomerase.

3. Oxidation to Pyruvate and Energy Production

Each triose phosphate undergoes a series of reactions that generate ATP and NADH.

1. G3P + NAD⁺ + Pi → 1,3‑bisphosphoglycerate + NADH + H⁺ (GAPDH)
2. 1,3‑BPG + ADP → 3‑phosphoglycerate + ATP (PGK)
3. 3‑PG → 2‑PG → phosphoenolpyruvate (PEP) (enolase)
4. PEP + ADP → pyruvate + ATP (pyruvate kinase)

Net yield per glucose molecule: