5) Unit 1 - Ligand Binding and Conformational Change

Question 1

where sites do ligands bind to on enzymes and proteins.

and what effect does this have

Answer 1

Ligands bind to an enzymes active site or a proteins binding site

effect:
this causes a conformational change, which causes a functional change

Question 2

Describe the induced fit model including the following:

• conformational change
• release of product

Answer 2

1) In enzymes, the site in which a specific substrate fits into, is called the active site
2) on binding the active site of the enzyme changes to better complement the substrate. The enzyme therefore undergoes conformational change
3) After the reaction has been catalysed the enzyme undergoes conformational change and resumes its original shape and products are released.

Question 3

How does the conformational change of enzymes during induced fit lower activation energy

Answer 3

by orienting the reactants so they are close enough and at the right geometry to react.

Question 4

what is an allosteric enzyme

Answer 4

enzymes that change their conformation upon the bind of a modulator to their allosteric site

Question 5

what is the benefit/purpose of modulators

Answer 5

control enzyme activity

Question 6

list the 2 types of moldulators

Answer 6

positive and negative

Question 7

describe positive modulators

Answer 7

• these stabilise the active form of an enzyme

* they increase rate of reaction by allowing enzyme to carry out its function

Question 8

describe negative modulators

Answer 8

• these stabilise the inactive form of an enzyme

* decrease the rate of reaction by inhibiting enzyme from carrying out its function

Question 9

what structure of protein (i.e primary, secondary etc) will show co-operativity

Answer 9

quaternary

Question 10

what is co-operativity

Answer 10

changes in one subunit, (due to a ligand) alters the affinity of the remaining subunits

Question 11

Describe co-operativity in regards to oxygen and hemoglobin

Answer 11

1) Hemoglobin shows co-operativity.
2) It had 4 subunits capable of binding to oxygen

3) When 1 subunit binds to a molecule of oxygen, the second binds more easily, the third easier and so on
(increasing affinity)

4) When 1 subunit releases a molecule of oxygen, the second releases it more easily, the third easier and so on
(decreasing affinity)

Question 12

Describe the effect of changing temperature and pH on the binding and release of oxygen in Hemoglobin

Answer 12

increase in temp - affinity for oxygen decreases

decreases in pH - affinity for oxygen decreases