L15 - Carbohydrate Metabolism 1.3 Flashcards
For glycolysis to continue what must be reformed and why?
For glycolysis to continue NAD+ must be continuously regenerated from the NADH formed by glyceraldehyde-3-P dehydrogenase
This can happen either anaerobically or aerobically
What are the 2 ways that NADH is regenerated and why are they important?
1) Production of lactic acid (lactate)
This process is described as fermentation, it is important in a number of situations:
- Manufacture of cheese, yoghurt
- Production of silage
- In muscle under anaerobic conditions
2) Production of ethanol
This process is described as fermentation, it is important in a number of situations:
- Manufacture of beer, wines, spirits
- Manufacture of bread
- It is a two step process
How does lactate production reform NAD+?
NADH + Pyruvate NAD+ + Lactate
Give the 2 equations in the 2 step process that regenerates NAD+ from ethanol
1) Pyruvate ————> Acetaldehyde
2) Acetaldehyde + NADH ————-> Ethanol + NAD+
happens at the opposite to formaldehyde —> methanol
How is NADH regenerated aerobically?
1) NADH transferred from cytoplasm (site of glycolysis) into mitochondria
2) Oxidised via mitochondrial electron transport chain
3) 3ATP produced for each NADH entering the chain
What is the ATP yield of aerobic and anaerobic glycolysis
Anaerobic
- 2 ATP/glucose via substrate level phosphorylation
Aerobic
- 2 ATP/glucose via substrate level phosphorylation
- 6 ATP via oxidative phosphorylation from oxidation of 2 NADH through electron transport chain
Total yield of ATP from aerobic glycolysis is 8ATP/glucose
How is Pyruvate changed to Acetyl CoA
- A complex reaction catalysed by pyruvate dehydrogenase
- Involves 7 steps and 6 coenzymes or cofactors
- During the reaction NAD+ is reduced to NADH+H+ - 3 ATP per pyruvate via oxidative phosphorylation
What are the 6 coenzymes used to change pyruvate to acetyl CoA?
TPP Lipoic Acid CoA FAD NAD+ Mg2+
