citric acid cycle

Question 1

How does the CAC add carbon to be oxidiased and where does this come from

Answer 1

Acetyl-CoA is added into the cycle in the mitochondiral matrix, oxidised and produces 2CO2, 3NADH, FADH2, ATP

Acetyl-CoA within the matrix from PDH reaction after glycolysis or beta oxidation of FFA

Question 2

What are the two stages of the CAC

Answer 2

Carbon removal stage - adds carbons, rearangment, remove carbon x2
- has energy capture

Molecule renegeration stage - regenerates oxaloacetate from succine-CoA
- has energy capture

Question 3

What are the important steps within the carbon removal stage of the CAC

Answer 3

1. hydrolysis of CoA from acetyl-CoA powers addition of 2c to oxaloacetate to form 6C molecule citrate
2. Citrate undergoes a 2 stage (dehydration -> hydration) isomerisation to enable decarboxylation
3. C1 removal 2 steps: oxidative decarboxylation - pt1oxidation, NAD+ reduced pt2 decarboxylation -> releases CO2
4. C2 removal oxidative decarboxylation - COO- replaced with CoASH releasing CO2

Question 4

What are the important steps within the regerative phase of the CAC

Answer 4

CoA removed from succinate to power a SLP - GDP->ATP (envrionmental phosphate)
succinate -> oxaloaceteate = 3 step process
oxidation - 2H removed FAD->FADH2 (complex 2 of ETC)
hydration - H2O added across double bond
oxidation - 2H removed NAD->NADH

Question 5

What is the overall reaction of the CAC

Answer 5

acytel-CoA + 3NAD + 2H2O + FAD + GDP + P -> 2CO2 + GTP + 3NADH/H+ + FADH2 + CoASH

Question 6

What is the consequences of inhibition of the CAC + molecule which inhibits the CAC

Answer 6

Fluroacetate -> Flurocitrate (instead of acetl-CoA)
Flurocitrate binds tightly to isomerise citrate acting as an irreversable inhibitor

effect:
prevents CAC from functioning -> build up of AcetylCoA leading to reduction of driving force for other pathways
Less reduced Coenzymes
Low ATP production