lecture 13 TCA Flashcards
purpose of citric acid cycle?
harvest high-energy electrons (captured in the form of NADH and FADH2) from acetyl CoA as it is oxidized to CO2
what’s the point of capturing energy in the form of NADH and FADH2 from TCA cycle?
These reduced molecules will create the proton gradient that powers ATP synthesis
The key control points in the citric acid cycle are the reactions catalyzed by :
isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.
____controls entry of glucose-derived acetyl CoA into the cycle.
pyruvate dehydrogenase
name the locations where the 3 NADH’s are generated in the citric acid cycle
isocitrate -> a-KTG, a-KTG->succinyl coA, malate -> oxaloacetate
___ is both a final product and a starting substrate
Oxaloacetate
overall reaction TCA cycle
3 NAD+ + FAD+ acetyl co-A + ADP + P —> 3 NADH + FADH2 + ATP + coA
name the 3 transamination reactions
- Transamination reactions convert alanine into pyruvate as α-ketoglutarate is converted into glutamate. Aspartate becomes oxaloacetate in the same manner.
- Glutamate can be deaminated directly to form α-ketoglutarate.
which steps create CO2?
isocitrate to a-KTG and aKTG to succinyl coA
what’s the point of CO2 here?
waste product- gets expelled
a-KTG + coA = ?
succinyl coA
the enzyme for this reaction adds a high energy thioester bond to coA, releasing CO2 in the process and converting NAD+ to NADH
a-KTG to succinyl coA
like NADH, ___ is an energy carrier that carries electrons to the electron transport chain
FADH2
which step involves substrate level phosphorylation
succinyl co A to succinate. why? because we’re ripping off that high energy thiol bond
what is formed from the oxidative decarboxylation of a-KTG?
succinyl coA
a-ketoglutarate dehydrogenase complex
three kinds of enzymes that is structurally similar to
the pyruvate dehydrogenase complex.
explain what happens when succinyl coA becomes succinate
energy inherent in the thioester molecule is transformed into phosphoryl-group-transfer potential, an example of substrate-level phosphorylation
what’s the big difference between citrate and isocitrate?
The isomerization of citrate to isocitrate moves a hydroxyl group with a hydrogen group, bringing it closer to the COO-
what are the 2 control points in the TCA?
isocitrate dehydrogenase and a-ketoglutarate dehydrogenase.
Isocitrate dehydrogenase is allosterically
stimulated by :
ADP, which signifies the need for more energy.
a-ketoglutarate dehydrogenase
is inhibited by high levels of :
ATP. Thus, the rate of the cycle is decreased when the
cell has high levels of ATP and NADH.
where specifically does TCA cycle occur
mito matrix
