Concept explainers
(a)
Interpretation:
The sequence of steps for the given reaction involving the adenylation of aspartic acid, is to be determined.
Concept Introduction:
The adenylation of aspartic acid takes place in three steps. In the first step, aspartic acid reacts with ATP. The pyrophosphate is the leaving group in this
Answer to Problem 25.40AP
Step 2:
Step 3:
Explanation of Solution
The adenylation of aspartic acid takes place in three steps.
Step 1: In the first step, aspartic acid reacts with ATP. The pyrophosphate is the leaving group in this
Step 2: In the second step, glutamine displaces AMP by a nucleophilic acyl substitution reaction.
Step 3: The intermediate produced in the step 2 undergoes hydrolysis to the form of glutamic acid and asparagine.
The sequence of steps for the given reaction involving the adenylation of aspartic acid is as shown above.
(b)
Interpretation:
The utilization of ATP in the equilibrium between glutamine and asparagine, is to be explained.
Concept Introduction:
ATP hydrolysis reactions are highly favorable. The reaction is used to help less favorable reactions which occur in high yield. In the adenylation of aspartic acid, the AMP group is a better leaving group than the hydroxyl group.
Answer to Problem 25.40AP
ATP is highly energetically favorable and produces AMP, which is a better leaving group than
Explanation of Solution
To make the less favorable reactions occur in high yield, the high energetic favorability of ATP is utilized. AMP is a better leaving group than
ATP is highly energetically favorable and produces AMP, which is a better leaving group than
(c)
Interpretation:
The
Concept Introduction:
The free energy change of two or more reactions can be used to determine the free energy change of a third reaction. The reactions are treated just like algebraic equations.
Answer to Problem 25.40AP
Explanation of Solution
_____________________________________________________________________
The
(d)
Interpretation:
The meaning of ATP hydrolysis in biosynthesis of asparagine is to be explained.
Concept Introduction:
ATP hydrolysis is a high energy reaction. It drives other reactions coupled to it, to completion.
Answer to Problem 25.40AP
If ATP is removed from the process, then the reaction is unfavorable. ATP drives the reaction to completion.
Explanation of Solution
If ATP is removed from the process, then the reaction is unfavorable. ATP does not actually undergo hydrolysis, but when coupled to the adenylation of aspartic acid, it becomes favorable and drives the reactions towards completion.
If ATP is removed from the process, then the reaction is unfavorable. ATP drives the reaction to completion.
(e)
Interpretation:
The reaction that ensures the completion of asparagine biosynthesis, is to be determined.
Concept Introduction:
Pyrophosphatase catalyzes the irreversible conversion of pyrophosphate to phosphate. This reaction ensures the completion of asparagine biosynthesis.
Answer to Problem 25.40AP
The other reaction which drives asparagine synthesis towards completion is the conversion of pyrophosphate to phosphate.
Explanation of Solution
The other reaction which drives asparagine synthesis towards completion is the conversion of pyrophosphate to phosphate, which is irreversible. Pyrophosphate is generated as a by-product during the adenylation of aspartic acid.
The other reaction which drives asparagine synthesis towards completion is the conversion of pyrophosphate to phosphate, which is irreversible.
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Chapter 25 Solutions
Organic Chemistry
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