Transition Stage After Glucolysis And Regulation

Question 1

What is decarboxilation

What enzyme mediates transition stage and name its 3 compartments

Answer 1

-removal of carbon atom

-pyruvate dehydrogenase complex
1 pyruvate dehydrogenase
2 dihydrolipoamide acetyl transferase
3 dihydrolipoamide dehydrogenase

Question 2

Effect of pyruvate dehydrogenase complex

Answer 2

• pyruvate cleaved into acetyl and Coenzyme A added to form Acetyl CoA
• NADH formed and goes to electron transport chain

Question 3

Describe what happens in pyruvate dehydrogenase ( E1 ) and the enzymes present inside

Answer 3

• has thiamine binded to pyrophosphate ( TPP )
• reacts with pyruvate and removes a c atom as CO2
• TPP-acetyl gives acetyl into next enzyme sub complex ( dihydrolipoamide acetyl transferase )

Question 4

Describe what happens in dihydrolipoamide acetyl transferase ( E2 ) and the enzymes present inside

Answer 4

• has lipoate which 2 sulphur atoms on disulfide bonds
• lipoate reacts with TPP-acetyl and takes the acetyl
• 1 sulphur holds the acetyl and other reduced and is now SH ( thiol )
• S-acetyl gives up acetyl group to CoA in E2 and lipoate forms 2 thiols and now acetyl-CoA formed

Question 5

Describe what happens in dihydrolipoamide dehydrogenase ( E3 ) and the enzymes present inside

Answer 5

• thiol groups protrude into E3
• FAD picks up 2H and forms FADH2
• NAD+ picks up the hydrides and forms NADH and goes to electron transport chain

Question 6

Which enzyme sub complex is point of regulation

Answer 6

• E1 ( pyruvate dehydrogenase)

Question 7

List the 2 regulatory enzymes in transition stage

Answer 7

1 pyruvate dehydrogenase kinase

2 pyruvate dehydrogenase phosphatase

Question 8

How does PDK regulate acetyl-CoA formation

Which substrates bind to
1 activation
2 inhibiting
Allosteric sites

Answer 8

-has phosphate extensions which contact E1 phosphorylating it and inhibiting it

1 ATP , Acetyl-CoA , NADH
2 pyruvate, ADP ( increase means ATP decrease )

Question 9

Receptors on E1 , what they bind to and effect

Answer 9

-bind to NADH and ATP and E1 inhibited

Question 10

What does Pyruvate dehydrogenase phosphatase do

Which 2 molecules can activate it

Answer 10

-has extensions which remove phosphate molecules from E1 and allowing it to function

• Ca2+
• insulin

Question 11

What does thiamine deficiency lead to

Answer 11

1 reduced ATP synthesis
2 beri beri - neurological conditions , pain , edema , paralysis
3 wernickle-korsakoff syndrome - psychosis