Important chemistry for two PDH cofactors Flashcards
1
Q
Thioesters
A
2
Q
Why thioesters high energy:
A
- not very good resonance stabilization in thioester in comparison to an oxygen ester…
Sulfur is bigger atom, so has poorer orbital overlap.
Forming a carboxylate in both cases. So free energy of hydrolysis is less for C=O, and higher for C-S.
C-S is high energy due to bad orbital overlap…
Another reason:
Before the thiol is protonated, weaker base and better leaving group, whereas the OH of an oxygen ester before protonation is a poor leaving group
3
Q
flavin cofactors
A
found in FAD, able to do 2 electron redox rxns in 2 steps.
It is a proton + e- in every case that there is a redox rxn occurring.
