Carbohydrate Metabolism 2

Question 1

The TCA cycle is located in?

Answer 1

Mitochondrial matrix

Question 2

Importance of PDH reaction

Answer 2

Commits pyruvate to TCA cycle;
Controls entry of glucose into TCA cycle;
Rate limiting step;
Irreversible;
Regulated - Allosteric, covalent, hormonal (insulin activates)

Question 3

Pyruvate dehydrogenase

Answer 3

Multienzyme complex;
Molecular mass - 4-10 mill daltons;
Consists of 2 enzyme complexes;
5 coenzymes;

Question 4

3 enzyme activities of PDH

Answer 4

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

Question 5

5 coenzymes of PDH

Answer 5

FAD+ - riboflavin (vit B2);
NAD+ - Niacin (vit B3);
CoA;
Thymine pyrophosphate (TPP) - thiamine (vitamin B1);
Lipoamide;

Question 6

Arrangement of E1, E2, E3

Answer 6

E1 - (alpha 3) - outermost;
E2 - (alpha2, beta 2) - innermost;
E3 - (alpha beta) - middle;

Question 7

Medical problems associated with PDH

Answer 7

Beri beri (thiamine deficiency) - Damage to PNS and weakened muscle;
Mercury and arsenite poisoning -  binds to E2 and affects CNS;
Vitamin deficiencies - riboflavin and niacin are components of FAD and NAD;
Pyruvate dehydrogenase deficiency - lacticacidemia (anaerobic carbohydrate metabolism); reduced ATP synthesis; elevated alanine;