Fallis Flashcards
Hard acids prefer what?
Hard bases
Soft acids prefer what?
Soft bases
8 examples of hard acids
+H+, Li+, Na+, K+, Mg2+, Ca2+, Cr3+ and Co3+
5 examples of hard bases
RNH2, NH3, O donors (H2O, OH-, RO-), F- and Cl-
6 examples of soft acids
Cu(I), Ag(I), Au(I), Hg(I), Hg(II) and Ti(I)
Rank the soft bases from softest to least
I- > Br- > CO > CN-
4 examples of borderline acids
Fe2+, Co2+, Cs+, Pb2+
7 examples of borderline bases
RCO2-, imidazole, N2, N3-, Br-, NO3- and SO42-
How are high reaction rates achieved by the entatic effect?
mimicking the transition state of the catalysed reaction, or the enzyme binds the TS more strongly than starting materials and products
What oxidation states are cycled by Rubredoxin?
Fe2+ and Fe3+
How does rubredoxin cycle between both oxidation states of Fe?
2+ longer bond length, so an intermediate bond length is used and metal is distorted towards the TS
Cu (I) prefers what kind of donors? Give an example
Soft donors - eg S
Cu (II) prefers what kind of donors? Give 2 examples
Hard donors - eg N & O
what’s the relationship between oxidation state and bond lengths generally?
Increasing ox state leads to ionic radius contracting and shorter bond lengths
What does the coordinated water molecule on a Zn enzyme act as?
A resting state, which can be replaced by a substrate
What catalyst would be needed for CO2 and why?
CO2 is both a LA and LB so requires a bifunctional LA/LB catalyst
What re the uses of synthetic modelling?
To make models that look like a natural system and that have the natural system’s function
what to SODs catalyse
the dismutation of superoxide radicals into molecular oxygen and hydrogen peroxide
Describe the bovine erythrocyte SOD
Dinuclear Cu and Zn centres, bridging His residue with His residues, 1 Asp, 1 Arg and 1 Thr
How can small anions (F- and N3-) affect Cu,Zn dinuclear/boving erythrocyte SODs?
Can compete with superoxide to act as inhibitors, binding to the active site
Mn3+ SOD suggests what mechanism?
inner sphere
Mn2+ SOD suggests what mechanism?
outer sphere
If 2 reactions differ by ~0.4V or more, will the reaction go to completion?
yes
where does Cytc transfer electrons to?
from cytochrome c reductase to cytochrome c oxidase
Questions about mutations of enzymes
does charge at active site change? if it does, affects electrostatics and E
HSAB arguments
What to look out for if a reaction is reversible or irreversible?
If E=0.4V or higher it’s irreversible!
Why does pKa of water lower as oxidation state increases?
as ox state increases, metal pulls ED of the water molecules towards itself, tendency of water to release protons increases
examples of PCET
dismutation of superoxide and oxidation of water to molecular oxygen in photosynthesis
Role of tyrz in PSII
tyrz is oxidised by the energy of P680+, resetting the ability of P680 to absorb another photon and release another photo-dissociated electron
pH = …. (ratios!)
pH = pKa + log [A-]/[HA]
