TCA Cycle Flashcards
what are the major products of the TCA cycle?
GTP, NADH and FADH2
these can produce large amounts of free energy in the form of ATP via oxidative phosphorylation
what’s the overall process of TCA? (short and sweet)
TCA oxidizes the acetyl fragment of acetyl CoA to CO2
In the process, 8 high every e- are captured in the form of NADH and FADH2
AcetylCoA –> 8 e- + ATP + 2CO2
what are the two major functions of TCA?
- energy production
2. biosynthesis
where does the TCA cycle happen?
mitochondria
what is another name for the TCA cycle?
Krebs
why is acetyl CoA what’s used in TCA?
- it’s the common product of catabolism of fat, carbohydrates, and proteins = you’re producing most of the reduced coenzymes that are used to make ATP in the ETC
- provides intermediates for other anabolic reactions
- glucose formation from AA carbon skeletons
what are the two stages of TCA?
- two carbons are introduced into the cycle by condensation of an acetyl group with oxaloacetate –> these two carbons leave the cycle as CO2 late when citrate undergoes two oxidative decarboxylations
- oxaloacetate is regenerated by oxidizing a 4 carbon unit
does the TCA generate ATP or use oxygen?
Not really - no ATP is directly generated or oxygen used in the TCA cycle
the TCA cycle doesn’t really generate a large amount of ATP nor use oxygen (besides the acetyl group being oxidized to CO2)
it removes e- from citrate and uses them to form NADH and FADH2 which enter the ETC to generate a proton gradient used to make ATP
**TCA cycle will not proceed in the absence of oxygen!!!
how are the TCA cycle and ETC connected?
TCA is the first stage in cellular respiration! it removes high energy e- from carbon fuels which reduce O2 to generate a proton gradient
the proton gradient is used to make ATP
reduction of O2 and synthesis of ATP are oxidative phosphorylation
what two things make up oxidative phosphorylation?
- reduction of O2 in the ETC
2. synthesis of ATP via the proton gradient produced
what are syntheses?
enzymes that catalyze a synthetic reaction in which two units are joined usually without the direct participation of ATP or any other nucleoside triphosphate
what is the first reaction of TCA?
citrate synthase catalyzed the condensation of oxaloacetate with acetyl CoA
what can citrate be used for outside of TCA?
- it’s an intermediate of the TCA cycle
- a source of acetyl CoA for the cytosolic synthesis of fatty acids and cholesterol
- it’s an allosteric effector that inhibits PFK1 in glycolysis and activates acetyl CoA carboxylase in fatty acid synthesis
what is the 2nd step of TCA? why does it happen?
citrate is isomerize into isocitrate via aconitase enzyme
there’s an interchange of H and OH groups on carbon 2 and 3 when you remove water and then put it back in
this step happens because citrate isn’t optimally suited for the oxidation reactions!
what is the 3rd step in TCA?
isocitrate is oxidized and decarboxylated to alpha-ketoglutarate via isocitrate dehydrogenase
a high energy electron is captured in the form of NADH and a CO2 is produced
isocitrate dehydrogenase is inhibited under energy-rich conditions by high levels of NADH and ATP
