Biochem theory: enzymes

Question 1

4 effects of E.S formation

Answer 1

1. A decrease in entropy of s
2. Desolvation (removal of h2o shell)
3. Induced fit (enzyme adjust to shape of substrate)
4. Alignment of the groups that must react

Question 2

What does enzyme change in reaction

Answer 2

Just the ts- not the energy of substrate or profuct, or keq

Question 3

3 ways enzyme recognises and bind a substrate

Answer 3

1. Shape consistency or fit (lock and key)
2. Electrostatic consistency (correct matching of ionic and h-bonds within active site
3. Thermodynamic consistency (can protein flex to adapt to substrate- vice versa)

Question 4

3 things binding energy is also used for

Answer 4

1. Desolvation: water shell needs to be removed for rxn (analogy txting)
2. Entropy reduction: holds substrates close together in proper orientation for rxn
3. Strain reduction: steric and/or electronic strain must be accommodated

Question 5

Enzyme specificity

Answer 5

1. Optical chiral (only bind to d or L)
2. Geometric (only in trans not cis- vice versa)

Question 6

Mechanisms of enzyme catalysis

Answer 6

1. Weak interactions between metal and substrate help stabalize charged ts and may help orient/bind the substrate
2. Metals accept and donate e in redox rxns

Question 7

Competitive inhibitors

Answer 7

Looks like substrate but not- enzyme bind but no products

Change in graph: kmat vmax/2 for inhibitor increase (meaning lower affinity since takes more substrate to reach vmax)

Question 8

Non-competitive

Answer 8

Inhibitor binds at site distinct from substrate site- usually allosteric site

can bind to free enzyme or to ES. if I to E binding affinities sane as ES binding affinity km is the same. but since inhibitor decreases active energy total, vmax decreases

if binding affinity greater for free enzyme: shift to E.S breakdown (meaning affinity low and km high)

Question 9

Mix inhibition

Answer 9

Occurs in non-competitive inhibition when affinity differs vmax and km changed

Since vmax down we are dividing by smaller number so intercept is higher

Question 10

Uncompetitive

Answer 10

I binds to allosteric site but only to E.S complex. Slope of 1/vo vs 1/s are unchanged but vmax lower and so is [s] needed to reach 1/2 vmax =km

Question 11

allosteric enzyme graph shape and why

Answer 11

sigmoidal, enzyme don do anything when [s] increases until it deems a worthy response

Question 12

allosteric enzyme: how does it behave

Answer 12

cooperativity- one switch, the next one does, and the next one does too, etc

Question 13

allosteric enzyme: low and high affinity and favour

Answer 13

low affinity= t-state= taut
high= R-state= relaxed
w/o S, eq favours T and weak binding
binding of S stabilizes r-state pulling equation to high affinity (cooperativity) law of mass action

Question 14

inhibitors/activators where it binds

Answer 14

inhibiters bind to T-state= pull equilibrium towards t state

activators bind to r-state= vice versa

activators and inhibitors don’t bind at the active site, but at other allosteric sites and can influence the r to T equilibrium of one protein

Question 15

regulation occurs…

Answer 15

at beginning of path to prevent waste of energy/effort

easy to shut pathway and just start over (quick adjustments/efficient)

Question 16

allosteric enzyme advantages

Answer 16

in mm enzyme, velocity alr goes up after tiny S added. doesnt wait for critical value

allosteric= sensitive to S and strategic

Question 17

zymogens

Answer 17

activated by cutting

excreted in off position (so wont digest of your own tissue)