Cell Metabolism 1 - Fates Of Pyruvate

Question 1

Three fates of pyruvate

Answer 1

• alcoholic fermentation
• lactate production
• acetyl CoA production

Question 2

1. Alcoholic fermentation

Answer 2

Characteristic of yeast

Anaerobic conditions

Pyruvate decarboxylated and then reduced and oxidised —> forms ethanol

Question 3

2. Generation of lactate

Answer 3

Characteristic of mammalian muscle

Anaerobic —> O2 limiting factor

Enzyme: lactate dehydrogenase

Question 4

Common purpose of alcoholic fermentation and generation of lactate

Answer 4

• allow NAD+ to be generated in conditions of O2 deprivation
• NAD+ needed in first step of generating ATP for the body —> dehydrogenation of G3P

Question 5

What reaction does Creatine kinase catalyse?

Answer 5

Creatine phosphate + ADP —> Creatine + ATP

Question 6

Why is Creatine phosphate needed/useful?

Answer 6

Amount of ATP needed during exercise is only enough for contraction for 1 second

Large reservoir of Creatine phosphate on hand to buffer demands for phosphate

Question 7

3. Acetyl CoA generation

Answer 7

Series of reaction in mitochondria

Pyruvate + HS-CoA + NAD+ —> acetyl CoA + CO2

Acetyl CoA formed is committed to TCA cycle

Enzyme: pyruvate dehydrogenase complex

Question 8

Primary source of acetyl CoA if you’ve eaten

Answer 8

Glucose

Question 9

Primary source of acetyl CoA in fasted state

Answer 9

Fatty acids

Question 10

Acetyl CoA bond

Answer 10

• thioester bond is high-energy linkage
  —> readily hydrolysed to donate acetate (2C)

Question 11

What is a cofactor for pyruvate deghydrogenation?

Answer 11

Thiamine pyrophosphate

Loses proton easily for pyruvate

Question 12

What is thiamine a derivative of?

Answer 12

Vit b1

Question 13

What can a deficiency of vit B1 lead to?

Answer 13

Beri Beri
—> thiamine needed as a cofactor to produce Acetyl CoA
—> brain cannot use fatty acids to produce acetyl CoA
—> cannot use glucose either as pyruvate dehydrogenase has an impaired function