Glycolysis

Question 1

Stage 1: Name of process, Substrate, enzymes, product.

Compare the enzymes Km. Coupled?

Answer 1

Phosphorylation. Glucose, to glucose-6-phosphate. Enzymes: glucokinase/hexokinase.

One ATP hydrolysis

Glucokinase: High Km so only active when glucose concentration is high, high Vmax.

Hexokinase: low Km therefore high affinity for glucose but low Vmax.

Question 2

Stage 2: Process, Substrate, enzyme, product. Coupled?

Answer 2

Isomerisation. Glucose-6-phosphate to fructose-6-phosphate. Enzyme: phosphoglucose isomerase

Question 3

Stage 3: Process, substrate, enzyme product. Coupled?

Answer 3

Phosphorylation. Fructose-6-phosphate to fructose-1,6-bisphosphate. Enzyme phosphofructokinase-1.

One ATP hydrolysis

Question 4

Stage 4: Process, substrate, enzymes, products. Coupled?

Answer 4

Splitting. Fructose-1,6-bisphosphate to DHAP and glyceraldehyde-3-phosphate (in equilibrium). Aldolase splits, triose phosphate isomerase interconverts products.

Question 5

Stage 5: Process, substrate, enzymes, products. Coupled?

Answer 5

Oxidation. Glyceraldehyde-3-phosphate to 1,3 biphospoglycerate by glyceraldehyde 3-phosphate dehydrogenase. As oxidation, reduces NAD+ to NADH.

Question 6

Stage 5: Process, substrate, enzymes, products. Coupled?

Answer 6

Substrate level phosphorylation. 1,3-biphosphoglycerate to 3-phosphoglycerate by phosphoglycerate kinase. Produces ATP from ADP.

Question 7

Pyruvate formation

Answer 7

3-phosphoglycerate to 2-phosphoglycerate by phosphoglycerate mutase. 2-phosholgycerate to unstable phosphoenolpyruvate by enolase (releases H2O). Phosphoenolpyruate to pyruvate via pyruvate kinase, coupled to ATP production.