The reaction catalyzed by citrate syn-thase, shown on the right, is the first step of the TCAcycle. In glycolysis, two key reactions to produce ATPoccur because an unfavorable reaction is coupled toanother reaction that is thermodynamically favorable.The reaction catalyzed by citrate synthase, shown onthe right, is similarly coupled to an unfavorable reac-tion in the TCA cycle. Write the unfavorable reactionusing structural formulas and write the key step thatdrives the two coupled reactions forward. What is theoverall AG'o of the coupled reactions?CH3-C>=0+S-COAAcetyl-CoA0-C-COO-CH₂-COOOxaloacetateH₂O COA-SHJcitratesynthaseCH₂-CHỌ—C—COOSOCH₂-COOCitrateAG'= -32.2 kJ/mol

Answered: The reaction catalyzed by citrate syn-…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Question

The reaction catalyzed by citrate syn-
thase, shown on the right, is the first step of the TCA
cycle. In glycolysis, two key reactions to produce ATP
occur because an unfavorable reaction is coupled to
another reaction that is thermodynamically favorable.
The reaction catalyzed by citrate synthase, shown on
the right, is similarly coupled to an unfavorable reac-
tion in the TCA cycle. Write the unfavorable reaction
using structural formulas and write the key step that
drives the two coupled reactions forward. What is the
overall AG'o of the coupled reactions?
CH3-C
>=0
+
S-COA
Acetyl-CoA
0-C-COO-
CH₂-COO
Oxaloacetate
H₂O COA-SH
J
citrate
synthase
CH₂-C
HỌ—C—COO
SO
CH₂-COO
Citrate
AG'= -32.2 kJ/mol

Expert Solution

TCA cycle

In glycolysis, a 6-carbon molecule of glucose-6-phosphate is broken down into 3-carbon pyruvate. It consists of 10 enzymatically catalysed reactions but all reactions do not produce ATP.

Pyruvate is oxidised to acetyl CoA by the enzyme pyruvate dehydrogenase Acetyl CoA delivers the acetyl group to the TCA cycle.

The TCA cycle uses this acetate and water to reduce NAD+ to NADH and FAD+ to FADH2. For every Acetyl CoA, we get 3NADH and 1 FADH2 and 1 GTP from TCA.