Prep For TCA Flashcards
After pyruvate is made from glycolysis where does its go
From the cytoplasm to the matrix of the mitochondria
After pyruvate (3 carbons) is sent to the mitochondrial matrix, what happens
Pyruvate is oxidized (loses 2 electrons) and decarboxylated (loses co2)
“Oxidatively decarboxylated”
To turn into acetyl coa (2 carbons)
What is the structure of acetyl coa
The acetyl group (c=o) is linked to the sh group of co enzyme A
This bind it’s called the thioester bond
If the thioester bond of the acetyl coa is hydrolyzed is it endergonic or excergonic
What does this mean
Highly exergonic meaning it has high acetyl group transfer potential
(can transfer its acetyl group very well to other molecules)
What is the conversion of pyruvate to acetyl coa called
What enzyme catalyzes this reaction
The bridge reaction or pyruvate oxidation
Pyruvate dehydrogenase
What are the three enzymes in the pyruvate dehydrogenase complex that turn pyruvate to acetyl coa
Pyruvate dehydrogenase (E1)
Dihydrolipoyl transacetylase (E2)
Dihydrolipoyl dehydrogenase (e3)
Why are e1 e2 and e3 needed for the bridge reaction
It allows the substrates from each reaction to move from one active site of the enzyme to that next
This short distance between all the Enzymes minimized side reactions and speeds up the reaction rate because it take less time to go from one place to the other
What is the prosthetic group of E1 and what reaction does it catalyze
TPP (thymine pyrophosphate)
Oxidative decarboxylation of pyruvate
What is the prosthetic group of E2 and what reaction does it catalyze
Lipoamide
Transfer of the acetyl group to coA
What is the prosthetic group of E3 and what reaction does it catalyze
FAD
Regeneration of the oxidized form of lipoamide
How are the enzymes situated in the pyruvate dehydrogenase complex
The e2 is at the core
E1 and e3 surrounding the core
What is the linker region
The region on E2that flips back and forth from e1 and e3
What five coenzymes does the pyruvate dehydrogenase complex need
TPP, LIPOAMIDE, FAD (catalytic coenzymes)
CoA, NAD+ (stoichiometric coenzymes, act as actual substrates)
How does first step the reaction catalyzed by e1 work
The TPP cofactor of E1 is in the ylid form (+ and - charges next to each other)
Pyruvate react with the carbanion of TPP
It’s becomes decarboxylated (lose co2) and becomes hydroxyethyl TPP
How does second step the reaction catalyzed by e1 work
The previously made hydroxy ethyl TPP is oxidized to an acetyl group (c=o)
Then the acetyl group gets transferred to Lipoamide (e2) where the Lipoamide disulphide bond is reduced
The e2 swings to the active site of e1 for this to happen