Carbs 3 Flashcards
What must happen to pyruvate before it enters the TCA cycle
converted to acetyl CoA
What enzyme is require to convert pyruvate to acetyl CoA
pyruvate dehydrogenase
Is the reaction from pyruvate to acetyl Co A reversible
no
What is a byproduct of converting pyruvate to acetly CoA
CO2
How is pyruvate dehydrogenase regulated
- acetyl CoA allosterically inhibits
- ATP, NADH inhibit
- ADP activates
Where does the TCA cycle occur
mitochondria
What is the importance of the TCA cycle
- generates reducing power
- useful intermediates
- all C-C and C-H bonds broken
What is required for the TCA cycle to occur
oxygen
oxaloacetate
What combines with acetyl CoA to form citrate
oxaloacetate C4
What enzyme converts the intermediate isocitrate to a-ketoglutarate
isocitrate dehydrogenase
What is the rate limiting enzyme in the TCA cycle
isocitrate dehydrogenase
what is the second necessary enzyme in the TCA cycle
a-ketoglutarate dehydrogenase
What are the products of the TCA cycle
- 6 NADH
- 2 FADH2
- 2 GTP
What are the uses of the intermediates
citrate- fatty acids
a-ketoglutarate- amino acids
succinate- amino acids, haem
malate- amino acids
oxaloacetate- amino acids, glucose
How is oxaloacetate replenished
pyruvate + CO2 + ATP + H2O –> oxaloacetate + ADP + Pi + 2H+
enzyme: pyruvate carboxylase
How are intermediates in the TCA cycle replaces
breakdown of amino acids
How is the TCA cycle regulated
ATP/ADP ratio
NADH/NADP ratio
isocitrate dehydrogenase allosterically regulated
Where does stage 4 of metabolism occur
inner mitochondrial membrane
What do NADH and FADH2 contain
high energy electrons
How does the ETC work
- electrons from NADH and FADH2 transferred through a series of carrier molecules called proton translocating complexes to oxygen
- so NADH and FADH2 become oxidised to NAD and FAD and PTC become reduced
What do the PTCs do with the free energy transferred to them by NADH and FADH2
move protons from matrix to intermembrane space as inner membrane itself is impermeable to protons
What does the movement of protons across inner membrane create
proton motive force and electrochemical gradient
what is the proton motive force used for
as protons can only move back through ATP synthase gives the energy for ATP synthesis
What is oxygen used for
terminal electron acceptor
What are the ETC and oxidative phosphorylation said to be
tightly coupled
what is the net yield of ATP from glycolysis
- 2 ATP
- 2 NADH= 5 ATP
What is the yield of ATP from formation of acetly CoA
2 NADH= 5ATP
What is the yield of ATP from the TCA cycle
2 GTP= 2ATP
6 NADH = 15 ATP
2 FADH2 = 3 ATP
What is the overall net yield of ATP
32 ATP per glucose
What are some inhibitors of ETC
anaerobic conditions
CO
CN (cassava)
How do inhibitors stop ETC
they bind to the haem group in PTC3 so oxygen not bound so cannot act as terminal electron acceptor so electron transport
How do uncouplers stop oxidative phosphorylation
uncouplers increase permeability of inner membrane to protons so dissipate proton motive force as heat
What are some examples of uncouplers
dinitrophenol
dinitrocresol
Where is brown adipose tissue found
newborns
hibernating animals
Why is brown adipose tissue useful for infants
contains natural uncoupling proteins to generate heat as they cannot shiver
UCP1 most important as it contains thermogenin
What is the difference in ox and substrate phosphorylation in terms of enzymes
ox: require mitochondrial membrane-bound complexes
sub: soluble membranes
What is the difference in ox and substrate phosphorylation in terms of
directness
ox: indirect as energy from proton gradient
sub: direct, energy from hydrolysis of high energy bond
What is the difference in ox and substrate phosphorylation in terms of oxygen
ox: requires O2
sub: can occur without
