Q/A Session 2

Question 1

How many subunits does haemoglobin have?

Answer 1

• 4

- 2x alpha and 2x beta subunits

Question 2

What does each unit consist of?

Answer 2

• A globin (protein part)

- A heam (non-protein part)

Question 3

A large portion of the haem group is

Answer 3

non-polar

Question 4

Haem Fe can bind how many ligands?

Answer 4

6 ligands

Question 5

How many of those 6 ligands are occupied by N atoms?

Answer 5

4/6

Question 6

What state must Fe be in for O2 to bind?

Answer 6

Fe2+

Question 7

What Histidine side chain is the N atom of?

Answer 7

HisF8

-Alpha helix F, 6=6aa of the helix

Question 8

HisF8 is also referred to as the

Answer 8

Proximal histidine

Question 9

What is the role of HisF7?

Answer 9

1. Prevents oxidation of haem Fe2+ when O2 binds (through a non-linear bond forming which sterically pushes 02 when it binds)
2. Ensures weak binding of O2 to ensure binding is reversible

Question 10

HisF7 is also referred to as the

Answer 10

Distal histidine

Question 11

T state means what and explain in reference to O2 affinity

Answer 11

T state= tense

Low O2 affinity

Question 12

R state means what and explain in reference to O2 affinity

Answer 12

R state= relaxed

High 02 affinity

Question 13

What state would you want to be in when exercising?

Answer 13

T state where there is low affinity to O2 so it will be released into surrounding tissues

Question 14

When is BPG produced?

Answer 14

When we ‘do work’ and break down carbohydrates

Question 15

When does BPG bind?

Answer 15

In the T state. It stabilises it keeping in the T state

Question 16

BPG is known as what kind of regulator?

Answer 16

An allosteric regulator

Question 17

How many negative charges does BPG carry?

Answer 17

5 negative charges

Question 18

What state does fetal heamoglobin spend most time?

Answer 18

• R state. Binds O2 better and doesn’t release it.

- The pocket is more negative due to change in aa therefore BPG won’t bind as effectively

Question 19

The Sequential Model shows

Answer 19

Different subunits can be in different configurations

Question 20

Concerted model shows

Answer 20

ALL subunits are ALWAYS in the same configuration

Question 21

What gives the sigmoidal curve?

Answer 21

Cooperativity

Question 22

What curve shape does haemoglobin show?

Answer 22

Sigmoidal

Question 23

What curve shape does myoglobin show?

Answer 23

Hyperbolic

Question 24

What model does Hb follow?

Answer 24

Concerted but has features of the sequential model

Question 25

What is an allosteric site?

Answer 25

Site on protein that’s not the active site, a regulatory molecule can bind here.

Question 26

What is an allosteric regulator?

Answer 26

Regulatory molecule that binds to allosteric site

Question 27

What is allosteric regulation?

Answer 27

Regulation of a molecule by binding an allosteric regulator to an allosteric site

Question 28

What is the Bohr effect?

Answer 28

Hemoglobin’s oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide

Question 29

What are three examples of allosteric regulators?

Answer 29

BPG, CO2, H+

Question 30

What state do they favour?

Answer 30

T state

Question 31

What is the effect of increased CO2?

Answer 31

1. Decrease in pH

2. Lowers affinity for O2

Question 32

Effect on O2 binding, BPG, CO2, pH, and H+ in R state

Answer 32

• O2 binding favoured
• Decrease in BPG
• Decrease in CO2
• Increase in pH
• Decrease in H+

Question 33

Effect on O2 binding, BPG, CO2, pH, and H+ in T state

Answer 33

• O2 release favoured
• Increase in BPG
• Increase in CO2
• Decrease in pH
• Increase in H+

Question 34

What happens in the MetHb condition?

Answer 34

The haem iron has been oxidised