Phosphorylation of serine residues is a common way to regulate the activity of p
ID: 1023685 • Letter: P
Question
Phosphorylation of serine residues is a common way to regulate the activity of proteins. The source of phosphate for phosphorylation is ATP. Here are the two reactions involved:
phosphoserine + H20 <==> serine + Pi G°' = -10.3 kJ/mol
ATP + H2O <==> ADP + Pi G°' = -30.5 kJ/mol
Using the information in the reactions above, which of the following are correct?
Question 8 options:
For the reaction
serine + ATP <==> phosphoserine + ADP G°'= -40.8 kJ/mol
Hydrolysis of ATP is an exergonic reaction.
Hydrolysis of phosphoserine is an endergonic reaction.
For the reaction
serine + ATP <==> phosphoserine + ADP G°'= -40.8 kJ/mol
Hydrolysis of ATP is an exergonic reaction.
Hydrolysis of phosphoserine is an endergonic reaction.
Explanation / Answer
The sum of the two reactions results in an overall negative free energy change under standard conditions.
The hydrolysis of ATP (Adenosine Triphosphate) to ADP (Adenosine diphosphate) and inorganic phosphate (Pi) is an exergonic reaction. ( G°' = negative)
The energy released from the hydrolysis of ATP into ADP is used to perform cellular work, usually by coupling the exergonic reaction of ATP hydrolysis with endergonic reactions.
Sodium-potassium pumps use the energy derived from exergonic ATP hydrolysis to pump sodium and potassium ions across the cell membrane while phosphorylaton drives the endergonic reaction.
Hydrolysis of ATP is an exergonic reaction. --------- Correct Answer