8. carbohydrate metabolism 2

Question 1

where does glycolysis occur?

Answer 1

in the cytosol

Question 2

where is the TCA cycle located

Answer 2

matrix of mitochondria

Question 3

what is the first thing that happens before the TCA cycle?

Answer 3

pyruvate forms acetyl coA by oxidative decarboxylation

pyruvate dehydroganse cataylses

Question 4

Importance of PDH reaction

Answer 4

• Commits pyruvate to TCA cycle
• Controls the entry of glucose to TCA cycle
• Rate limiting step
• Irreversible
• Regulated

–Allosterically

–Covalently

–Hormonally (insulin activates)

Question 5

Pyruvate Dehydrogenase structure

Answer 5

• Multienzyme complex
• Molecular mass 4 - 10 million daltons big
• Consists of 3 enzyme complexes
• 5 coenzymes

Question 6

3 enzyme activities of PDH

Answer 6

• E1 - Pyruvate decarboxylase
• E2 - Dihydrolipoyl transacetylase
• E3- Dihydrolipoyl dehydrogenase

Question 7

5 coenzymes of PDH

Answer 7

•Thiamine pyrophosphate (TPP) thiamine (vitamin B1)

•Lipoamide: lipoic acid - 10-carbon fatty acid with sulphydryl groups on C8 and C10

•CoA: pantothenic acid (vit B5)

•FAD+: riboflavin (vit B2). Prosthetic group bound covalent to E3 protein

•NAD+: niacin (vit B3)

Question 8

Answer 8

Question 9

Answer 9

Question 10

3 medical problems associated with PDH

Answer 10

1. Beri-beri (thiamine deficiency)

–Damage to peripheral nervous system and weakened muscle – CV disorders.

–Far East where polished rice is major component of diet.

2.Mercury and arsenite poisoning. Binds to dihydrolipoyl groups on E2. CNS pathologies.

•Vitamin deficiencies - riboflavin and niacin are components of FAD and NAD

3.Pyruvate Dehydrogenase deficiency genetic

Question 11

Answer 11

Question 12

overall molecules produced from one molecule of acetyl coA oxidised

Answer 12

3 NADH + 1 FADH2 +2CO2 + 1GTP

(4 pairs of electrons)

Question 13

Answer 13

not a lot of control

Question 14

medical problems associated with TCA cycle

Answer 14

none- major defect dont survive