ATP Flashcards
1
Q
Why is ATP useful as an energy currency?
A
It is relatively stable in aqueous solution
2
Q
Why is ATP relatively stable in aqueous solution?
A
Spontaneous ATP hydrolysis has an activation energy and so the reaction is kinetically slow
3
Q
How do cells ensure hydrolysis of ATP releases a large amount of free energy?
A
Living cells maintain a ratio of ATP/ADP that is far from equilibrium
4
Q
Give an example of an unfavourable reaction where ATP is coupled
A
Phosphorylation of glucose by hexokinase
5
Q
What is the mechanism by which hexokinase phosporylates glucose?
A
- Hexokinase binds 1 glucose and 1ATP in close proximity
- O on C6 glucose nucleophilically attacks the γ phosphate of ATP
- Phosphate electron pair is donated to the anhydride oxygen, bridging the β and γ phosphates of ATP
6
Q
Give an example of a favourable reaction where ATP is made
A
Dephosphorylation of PEP to form pyruvate
7
Q
What is the mechanism by which pyruvate kinase makes pyruvate from PEP?
A
- Pyruvate kinase binds a PEP and ADP in close proximity
- An oxyanion of the β phosphate of ADP performs a nuclephilic attack on C2 phosphoester of PEP
- Bond rearrangement with uptake of a proton from water produces pyruvate
