3B: CAC
Terms
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- where does CAC take place
- in the mitochondria
- how many carboxylic acids are on citrate?
- 3 - a tricarboxylic acid.
- How does pyruvate get from the cytosol to the mito matrix?
- by an antiporter, pyruvate carrier.
- what happens to pyruvate once it gets into the mito matrix?
- it is oxidatively decarboxylated by pyruvate dehydrogenase complex.
- what links glycolysis and CAC?
- oxidative decarboxylation of pyruvate to give acetyl CoA and CO2
- What does CoA do?
- carries Acyl groups
-
What are the components of CoA?
What is the reactive part? -
B-mercaptoethylamine unit
Pantothenate Unit
ADP
The thiol SH - how does acetate enter the CAC?
- thioester bonded to CoA.
- what's the diff between ATP and GTP?
- adenine and guanine
- What is Thiamine Pyrophosphate? (TPP)
- The prosthetic group of E1 on pyruvate dehydrogenase complex.
- what is the function of TPP?
- decarboxylate pyruvate
- what is the function of lipoamide?
- oxidize
- what is the function of Coenzyme A in PDHC?
- Acyl carrier
- What is the purpose of FAD in PDHC?
- to reoxidize lipoamide
- what is the function of NAD+ in PDHC?
- to reoxidize FADH2
- how come the reactive part of TPP is reactive?
-
The Carbon atom is between N and S, so very stable anion - acidic; deprotonates because pka is about 10.
Then the anion adds to pyruvate to form tetrahedryl intermediate. - E2 of PDHC
- dihydrolipoyl transacetylase
- What is E3 of PDHC?
-
Dihydrolipoyl dehydrogenase
-Oxidizes dihydrolipoamide to regenerate the coenzyme lipoamide. - what is the reactive center of TPP?
- a thiazolium ring (acidic carbon between a nitrogen and sulfur)
- how many atoms make up the long lipoamide arm of lipoic acid/lysine?
- 12
- what are the reactions that take place at E1 of PDHC?
-
1. Decarboxylation - add pyruvate to TPP, give of CO2.
2. Oxidation - oxidize TPP back, transfer Acetyl concomiantly to Lipoamide. - what are the reactions that take place at E2 of PHDC?
- only one; transfer of acetyl from acetyllipoamide to CoA to leave dihydrolipoamide (reduced form).
- How many enzymes and cofactors are in PDHC
-
3 enzymes
5 cofactors - What are the 5 cofactors in PDHC
-
TPP
Lipoamide
Coenzyme A
NAD+
FAD - What plays a central role in formation of Acetyl CoA from Pyruvate?
- LIPOIC ACID'S LONG ARM.
- What are the steps of PDHC?
-
1. Thiamine Pyrophosphate decarboxylates
2. Lipoamide Oxidizes the Acetyl group and transfers it to Coenzyme A.
3. FAD reoxidizes Lipoic Acid back to Lipoamide.
4. NAD oxidizes FADH2 back to FAD. - What is lipoamide linked to on WHICH ENZYME?
- a Lysine residue on Enzyme 2
- What are the cofactors bound to each subunit in TPHC?
-
E1: TPP
E2: Lipoamide, CoA
E3: FAD, NAD+ - What is a synthase
- an enzyme catalyzing a synthetic reaction in which 2 units are joined w/out participation of ATP or NTP
- what are control points for the CAC?
-
KDHC
PDHC
isocitrate dehydrogenase