10 - TCA and ETC Flashcards
What happens straight after pyruvate is formed?
- Pyruvate dehydrogenase (5 enzyme complex) oxidises pyruvate and adds CoA to form Acetyl CoA
- Occurs in mitochondrial matrix
- Irreversible loss of CO2 (regulatory step)
If you had a PDH deficiency, e.g due to genetics, what would happen?
Lactic acidosis, build up of pyruvate so would be converted to lactate by LDH to produce energy.
Why is Vitamin B important?
Produces co-factors, e.g FAD and lipoic acid, that held PDH and therefore keep healthy metabolism
What signals are PDH regulated by?
How does the TCA cycle work?
2 TCA per glucose
6 NADPH
2 FADH2
2 GTP
(2 CO2)
Summarise the key aspects of TCA
- In mitochondria
- Central pathway for sugars, FA, KB, AA, Alcohol
- Oxidative (Acetyl to 2CO2)
- Produce intermediates that lose CO2 easily to break C-C bonds
- Does not function in absence of O2
- Provides precursors for biosynthesis
- No net synthesis of intermediates
Where does regulation occur in TCA?
Isocitrate Dehydrogenase:
+ ADP - NADH, ATP (allosteric)
A-Ketoglutarate Dehydrogenase
- NADH, ATP, Succinyl CoA
Give some examples of how TCA products act as biosynthetic precursors.
C5/C4 - AA
C4 - Haem and Glucose
C6 - FA
Explain metabolism in terms of breaking bonds.
Breaking C-C bonds forming CO2
Breaking C-H bonds and storing in NAD and FAD
Where does most of the energy in catabolism come from?
NADH and FADH2 transferring electrons to O2, releasing large amounts of energy for ATP synthesis
When intermediates are removed from TCA for biosynthesis, what replaces them?
- Breakdown of other molecules, e.g AA
- Pyruvate Carboxylase
How many molecules of ATP are produced from each glucose and how many from each FADH2 and NADH?
- 32
- 2.5 NADH
- 1.5 FADH2
Energy released oxidation of these molecules used for oxidatitive phosphorylation
Explain the electron transport chain up to just before ATP synthase
- 3 PTC
- NADH oxidised. 2 electrons pass to PTC and energy from this used to transport 2H+ across membrane.
- FADH oxidised at 2nd PTC
- Electrons passed to each PTC and energy used to move H+.
- Generates a proton motive force (electrochemical gradient)
- Oxygen is terminal electron acceptor and combines with 2 electrons and 2 H+ to form water
How much of the energy from electrons is used to move H+ and what happens to the rest?
30%, rest of energy is lost as heat.
Tighter coupling, less energy loss to heat
Explain how ATP is synthesis via oxidative phosphorylation?
- Oxidation of NADH set up p.m.f
- Protons move down their gradient via ATP synthase
- Energy from this dissapation is used to phosphorylate ADP