L4 – CENTRAL SUGAR METABOLISM
GLYCOLYSIS (GLUCOSE + 2 ADP + 2 NAD + → 2 PYRUVATE + 2 ATP + 2 NADH + + 2 H + )
Two stages in glycolysis:
- Energy investment stage
- Pay off stage
1. ENERGY INVESTMENT STAGE (2 ATP INVESTED)
2 moles of ATP are invested at steps Hexokinase and Phosphofructokinase
1. Glucose is irreversibly phosphorylated by hexokinase, 1 ATP is invested
2. Glucose-6-P is converted into Fructose-6-P by isomerase
3. Fructose-6-P is irreversibly phosphorylated by phosphofructokinase, 1 ATP invested
4. Fructose-1,6-bisphosphate is reversibly converted into Dihydroxyacetone-P and
Gylceraldehyde-3-P by aldolase
- Phosphofructokinase is subjected to allosteric regulation
o Lower activity due to high ATP levels
o Important control point for glycolysis
o If there are a lot of ATPs present, no need for glycolysis
2. PAY OFF STAGE (1 GLUCOSE → 4 ATP & 2 NADH)
GLYCOLYSIS (GLUCOSE + 2 ADP + 2 NAD + → 2 PYRUVATE + 2 ATP + 2 NADH + + 2 H + )
Two stages in glycolysis:
- Energy investment stage
- Pay off stage
1. ENERGY INVESTMENT STAGE (2 ATP INVESTED)
2 moles of ATP are invested at steps Hexokinase and Phosphofructokinase
1. Glucose is irreversibly phosphorylated by hexokinase, 1 ATP is invested
2. Glucose-6-P is converted into Fructose-6-P by isomerase
3. Fructose-6-P is irreversibly phosphorylated by phosphofructokinase, 1 ATP invested
4. Fructose-1,6-bisphosphate is reversibly converted into Dihydroxyacetone-P and
Gylceraldehyde-3-P by aldolase
- Phosphofructokinase is subjected to allosteric regulation
o Lower activity due to high ATP levels
o Important control point for glycolysis
o If there are a lot of ATPs present, no need for glycolysis
2. PAY OFF STAGE (1 GLUCOSE → 4 ATP & 2 NADH)
