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Unformatted text preview: a double bond. TCA cycle
enzyme - part of complex 2 - the only
TCA cycle enzyme that is membrane
bound - part of complext two of elcetron
trasnport chain - embedded the
mithcondria. FAD bound to
dehydrogenase becuase of this reaction
- dones tcome on and off the enzyem. Accepting of electros - FADH doesn't come off the
molecules - no diffusion of FADH2 away from the
enzyme itself. indicate FAD being bound. Dehydrogenation
FAD is covalently bound to the enzyme
This enzyme is also part of the electron
transport pathway in the inner mitochondrial
4/6 and 4/8/13 MCB 2000 Lectures 22 & 23 FAD picks up e- one by one Accepts 1 elctrons at a time and added to central ring
s tucutre. - form a semiquinone - very reactive - can
undergo redox central. if the second elctrons dont
follow the ﬁ rst one - have a radial (radial damging to
macromolecules) one reason why you want to keep
FAD with this radical. 4/6 and 4/8/13 MCB 2000 Lectures 22 & 23 Fumarase Catalyzes the Trans-Hydration of
Fumarate to Form L-Malate Hydration across the double bond
Add water across double bond - last reaction matalte deodehydaase. 4/6 and 4/8/13 MCB 2000 Lectures 22 & 23 Malate Dehydrogenase Completes the Cycle
by Oxidizing Malate to Oxaloacetate Unfavorable - but made
possible by coupling. An NAD+-dependent oxidation
This reaction is energetically expensive:
Go' of +30 kJ/mol
The equilibrium favors malate; [OAA] is very low.
4/6 and 4/8/13 MCB 2000 Lectures 22 & 23 What Are the Energetic
Consequences of the TCA Cycle?
One acetate through the cycle produces
1 ATP (GTP),
4 reduced coenzymes:
These numbers double when expressed per
glucose molecule. for glucose - 2 acytl CoA - have to
double them 4/6 and 4/8/13 MCB 2000 Lectures 22 & 23 Allosteric regulation only - no hormonal regulation. non undergo phosphorlyation or dephosohproyatlon. Intermediates - like ketone bodies enter the
TCA cycle. TCA cycle is used by all nutrients (carbs, proteina nd fat) fee into the TCA cycle - operation all the time. the rate changes How Is the TCA Cycle Regulated?
r ate dependent on energy chagrge. chemically linked to the
electron transfer chain - TCA cycle going to slow down as well.
energy charge for regulation of pahtway that genereate ATP Citrate synthase
control by [OAA]eed ATP - TCA cycle goes faster. Citrate synthase (substrate)
c ondentation between 2
FBI by [citrate]OAA is the rate liminted carbons acetyl coA. importantto citrate
substrate - needs to coupled
Isocitrate dehydrogenase - rate-limiting
Isocitrate-rate liminintg ﬁ rst step
where you gnerate NADH.
c hemical link between TCA
ATP and NADH inhibit,cycle and the electron transport
c hain. NADH donate elctrons to
ADP and NAD
FBI by NADH and succinyl-CoA
Chemical mechanism idential (ketoglugrate and
ATP inhibits pryvuate dehydrogenase) -require same vitamin
Also note pyruvate dehydrogenase:
ATP, NADH, acetyl-CoA inh...
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This note was uploaded on 09/17/2013 for the course MCB 2610 / 200 taught by Professor Feldman during the Fall '12 term at UConn.
- Fall '12