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29 Cards in this Set

  • Front
  • Back
What vitamin precursor is CoA associated with?
B5... pantothenic acid
How many carbons are added with Acetyl-CoA... and how do you end up with 6-carbon needed for citrate?
two + 4 from oxaloacetate = 6
Are there many TCA related genetic enzyme abnormalities?
No
Describe the process of pyruvate being converted to acetyl CoA:
a. reactants and enzymes
b. products
c. ∆G°
a.Reactants:
• pyruvate
• NAD+
• CoASH
• pyruvate dehydrogenase

b.Products:
• acetyl CoA
• NADH
• CO2

c. c. ∆G° = -8.0 kcal/mol
.
Describe the pyruvate dehydrogenase complex.
a. number of subunits
b. number of dif enzmes
c. number of regulatory proteins.
d. number of coenzymes
.
a. number of subunits =60
b. number of dif enzmes = 3
c. number of regulatory proteins = 2
d. number of coenzymes =5
.
Name the first 3 enzymes of the pyruvate dehydrogenase complex and
b.their numbers and
c. their respective roles.
.
1. E1
a. Pyruvate dehydrogenase component (pyruvate decarboxylate)
b. 24 monomers
c. removes CO2 (carboxyl)

2. E2
a. Lipoamide redutase transacetylase (w/ TPP a temporary acetyl carrier)
b. 8 trimers
c. transfer the acetyl group to the HSCoA to make acetyl CoA.

3. E3
a. Dihydrolipoyl dehydrogenase
b. 12 monomers
c. a. Dihydrolipoyl dehydrogenase
b. 12 monomers
c. reoxidizes the transacetylase (recycle) in the process NADH is made and delivered to ETC.

.
What vitamin (and its deriviative) is associated with pyruvate decarboxylase, and as such the acetyl group is attached to it?
.
B1, Thiamine pyrophosphate (more specifically, the thiazolium ring)
.
What causes Wernicke-korsakoff Syndrome?
.
ability to uptake B1 is inhibited and poor diet... it's not because ethanol is a poor fuel.
.
What reoxidizes lipoamide reductase? and how?
dihydrolipoyl dehydrogenase reduces NAD+ to NADH, so in the process it reoxidizes lipoamide.
.
Describe citrate synthesis:
a. reactants
b. products
b. enzymes
c. ∆G° = ?
a. reactants
• oxaloacetate,
• acetyl CoA
• water

b. Products:
• citrate
• HSCoA
• H+

c. enzyme: Citrase synthase

d. ∆G° = -7.7 kcal/mol
.
Describe Isocitrate synthesis: (note: cis-aconitate is an intermediate)
a. reactants
b. products
b. enzymes
c. ∆G° = ?
a. reactants
• citrate

b. Products:
• isocitrate

c. enzyme: aconitase

d. ∆G° = 1.5 kcal/mol (driven by the favorable next rxn that pulls txn to the right).
.
Describe ∂-ketoglutarate synthesis:
a. reactants
b. products
b. enzymes
c. ∆G° = ?
a. reactants
• Isocitrate
• NAD+

b. Products:
• ∂-ketoglutarate
• NADH
• CO2

c. enzyme: isocitrate dehydrogenase

d. ∆G° = -5.3 kcal/mol
.
Describe Succinyl CoA synthesis:
a. reactants
b. products
b. enzymes
c. ∆G° = ?
a. reactants
• ∂-ketoglutarate
• NAD+
• CoASH

b. Products:
• succinyl CoA
• NADH + H+
• CO2

c. enzyme: ∂-ketoglutarate dehydrogenase

d. ∆G° = -8.0 kcal/mol.
.
Describe Succinate synthesis:
a. reactants
b. products
c. enzymes
d. ∆G° = ?
e. What does this rxn compete with?
.
a. reactants
• Succinyl CoA
• GDP

b. Products:
• Succinate
• GTP
• CoASH

c. enzyme: Succinyl-CoA synthase

d. ∆G° = -0.7 kcal/mol.
e. the rxn where the ketone body, acetoacetate is activated to be converted acetoacetyl CoA... however in the end succinate is still produced, but without GTP.
.
What step in the TCA cycle is CoA needed, without which the TCA cycle would stop? (not acetyl CoA)
∂-ketoglutarate to Succinyl CoA rxn.
Functionally, what is ∂-ketoglutarate dehydrogenase similar to?
Pyruvate dehydrogenase
Which TCA oxidation rxn, does not produce CO2 but FADH2 in its place?
Succinate to Fumarate
Describe Fumarate synthesis:
a. reactants
b. products
c. enzymes... what is special here?
d. ∆G° = ?
e. What is special about this oxidative TCA rxn?
.
a. reactants
• Succinate
• FAD

b. Products:
• Fumarate
• FADH2
• NOTE: NO CO2 PRODUCED HERE!!!

c. enzyme: Succinate dehydrogenase: attached to the inner mitochondrial membrane (matrix side).

d. ∆G° = -0 kcal/mol.
Describe Malate synthesis:
a. reactants
b. products
c. enzymes
d. ∆G° = ?

.
a. reactants
• Fumarate
• H2O

b. Products:
• Malate

c. enzyme: Fumarase

d. ∆G° = 0 kcal/mol.
Describe Oxaloacetate synthesis:
a. reactants
b. products
c. enzymes
d. ∆G° = ?
.
a. reactants
• Malate
• NAD+

b. Products:
• Oxaloacetate
• NADH
• NO CO2 PRODUCED HERE!!!

c. enzyme: Malate dehydrogenase.

d. ∆G° = +7.1 kcal/mol... very positive.


.
What are the three profoundly exergonic reaction, and thus highly regulated rxns?
.
• Citrate synthase (∆G° = -7.7 kcal/mol)
• isocitrate dehydrogenase (∆G° = -5.3 kcal/mol)
• ketogluterate dehydrogenase (∆G° = -8.0 kcal/mol)
.
What is the overall ∆G° for TCA
∆G° = - 13.1 kcal/mol
What percentage of energy available from the oxidation of acetyl CoA is capture in chemical form?
.
90% ( 206 kcal ÷ 228 kcals... in NADH, FADH2 and GTP)
What pulls the malate to oxaloacetate rxn?
Oxaloacete being converted to citrate.
What are the 4 key Kreb's enzymes that are regulate in the TCA cycle?
1. citrate synthase

2. isocitrate dehydrogenase

3. ∂-ketoglutarate dehydrogenase

4. pyruvate dehydrogenase
.
What are 2 ways citrate synthase regulation can inhibit the TCA cycle?.
1. product inhibition: [citrate] is to high
2. Allosteric control:
a. via ATP/ADP... ratio of 1 (being best) inhibits citrate synthase.
b. Also NADH/NAD ratio
.
How is the ∂-ketoglutarate dehydrogenase rxn (∂-ketoglutarate to succinyl CoA) involved in TCA regulation?
.
∂-ketoglutarate dehydrogenase undergoes product inhibition: these products include excess succinyl CoA and NADH.
.
What are the 2 ways the pyruvate dehydrogenase rxn (pyruvate to acetyl CoA) is involved in TCA regulation?
.
Pyruvate dehydrogenase is ihibited by:

a. Product inhibition:
• acetyl CoA
• NADH

b. Allosteric inhibition: ATP
.
What are the two proteins that inhibit pyruvate dehydrogenase and how do they function?
a. Kinase:
• [NADH an acetyl CoA]high --> kinase is allosterically acitve --> phosphorylated pyruvate dehydrogenase is inactive.

b. Phosphatase:
[NAD and CoASH] are high --> Phosphatase is allosterically activated --> removes phosphate from pyruvate dehydrogenase --> pyruvate dehydrogenase is activated.
.