L15 - Carbohydrate Metabolism 1.3 Flashcards

1
Q

For glycolysis to continue what must be reformed and why?

A

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

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2
Q

What are the 2 ways that NADH is regenerated and why are they important?

A

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
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3
Q

How does lactate production reform NAD+?

A

NADH + Pyruvate NAD+ + Lactate

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4
Q

Give the 2 equations in the 2 step process that regenerates NAD+ from ethanol

A

1) Pyruvate ————> Acetaldehyde

2) Acetaldehyde + NADH ————-> Ethanol + NAD+
happens at the opposite to formaldehyde —> methanol

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5
Q

How is NADH regenerated aerobically?

A

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

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6
Q

What is the ATP yield of aerobic and anaerobic glycolysis

A

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

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7
Q

How is Pyruvate changed to Acetyl CoA

A
  • 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
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8
Q

What are the 6 coenzymes used to change pyruvate to acetyl CoA?

A
TPP
Lipoic Acid
CoA
FAD
NAD+
Mg2+
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