1.23 b) Ligand Binding Changes the Conformation of a Protein

Question 1

What is a ligand?

Answer 1

A substance which can bind to a protein

Question 2

Under what circumstances does the conformation of a protein change?

Answer 2

if a ligand binds to a protein’s binding site (eg a substrate binds to an enzyme’s active site)

Question 3

Conformational changes in proteins causes ___ changes.

Answer 3

functional

Question 4

R groups not involved in protein folding can allow ___ to ligands.

Answer 4

binding

Question 5

Binding sites have a complementary ___ and ___ to the ligand.

Answer 5

shape, chemistry

Question 6

Induced fit is a ___ change in the shape of the ___ site, which increases the ___ interacting with the substrate.

Answer 6

temporary, active, area

Question 7

This chemical environment lowers the ___ ___ for the reaction.

Answer 7

activation energy

Question 8

Name the two sites that allosteric enzymes have.

Answer 8

active site and allosteric site

Question 9

Allosteric enzymes can change ___ upon binding a ___.

Answer 9

conformation, modulator

Question 10

In allosteric enzymes, modulators bind at secondary locations known as ___ ___.

Answer 10

allosteric sites

Question 11

Once the modulator has bound, the conformation of the enzyme changes which alters the ___ of the ___ ___.

Answer 11

shape, active site

Question 12

Modulators that increase the enzyme’s affinity for the substrate are called…

Answer 12

positive modulators

Question 13

Modulators that decrease the enzyme’s affinity for the substrate are called…

Answer 13

negative modulators

Question 14

Modulators bind to the ___ ___ and change the shape of the ___ ___.

Answer 14

allosteric site, active site

Question 15

What is cooperativity?

Answer 15

when a ligand binding to one subunit of a multi-subunit protein changes the affinity of the other subunits for that ligand

Question 16

In what type of proteins does cooperativity occur?

Answer 16

ones with quarternary structure

Question 17

What is an example of a molecule that exhibits cooperativity?

Answer 17

haemoglobin

Question 18

Haemoglobin has quarternary structure and so is made of 4 ___ ___.
Each one has a ___ group, capable of binding to a molecule of ___.

Answer 18

polypeptide chains.
haem, oxygen

Question 19

When one of haemoglobin’s subunits binds an oxygen molecule the remaining subunits bind with ___ ___.

Answer 19

increasing ease

Question 20

The reverse is also true, when the first of oxy-haemoglobin’s subunits releases its oxygen molecule, the remaining subunits release theirs with ___ ___.

Answer 20

increasing ease

Question 21

What are the two main factors that affect haemoglobin’s affinity to oxygen?

Answer 21

pH and temperature

Question 22

Describe how haemoglobin’s affinity to oxygen changes under the following conditions:
1. As temperature increases
2. As pH increases

Answer 22

1. affinity decreases.
2. affinity increases

Question 23

Describe the conditions in actively respiring tissue with respect to temperature and pH and; suggest a benefit to these conditions.

Answer 23

Actively respiring tissue has a high temperature and low pH;
this lowers haemoglobin’s affinity to oxygen, which promotes oxygen delivery to respiring cells (which require oxygen)

Question 24

Phosphates can cause ___ conformational changes in proteins.

Answer 24

reversible

Question 25

The addition of phosphate groups is a common form of __-__ ___.

Answer 25

post-translational modification

Question 26

What is the name of the enzyme that catalyses the addition of phosphate groups to other proteins?

Answer 26

protein kinase

Question 27

The phosphate group that is transferred by the enzyme ___ ___, comes from ___ (it is the ___ phosphate).

Answer 27

protein kinase, ATP, terminal/third

Question 28

What is the name of the enzyme that catalyses the reverse reaction (dephosphorylation)?

Answer 28

protein phosphatase

Question 29

Phosphorylation affects a proteins activity by causing ___ ___.

Answer 29

conformational changes

Question 30

Proteins can be ___ or ___ by phosphorylation. This is how many cellular proteins are ___.

Answer 30

activated, inhibited.
regulated

Question 31

Phosphate groups have a ___ charge (just like phosphorus ions haha cute)

Answer 31

negative

Question 32

Since phosphate groups have a negative charge, phosphorylation can disrupt the ___ interactions in the un____ protein, or create new ones.

Answer 32

ionic, unphosphorylated

Question 33

Name a protein who’s function is dependent on phosphorylation.

Answer 33

The sodium potassium pump (its phosphorylated by ATP to transport 3 sodiums out and dephosphorylated by ADP to transport 2 potassiums in)