Lesson 65 - Haemoglobin & dissociation curves

Question 1

Affinity definition

Answer 1

The degree to which a substance tends to combine with another (chemical attraction)

Question 2

What is meant with haemoglobin having a high or low affinity for O2?

Answer 2

• Haemoglobin with a high affinity for oxygen: will bind to O2 easily but release less easily
• Haemoglobin with a low affinity for oxygen - will not bind to oxygen easily but will release it easily

Question 3

What is the equation for formation of oxyhaemoglobin?

Answer 3

Haemoglobin + Oxygen ⇌ Oxyhaemoglobin

Question 4

What is partial pressure of oxygen?

Answer 4

A measure of oxygen conc.

Question 5

What is the structure of haemoglobin?

Answer 5

• A quaternary structure protein
• Made of 4 polypeptide chains
• Each chain has a haem group which contains an iron ion, where an O2 molecule can bind to

Question 6

Where is O2 loaded and unloaded in the body?

Answer 6

Alveoli in the lungs: High O2 conc. High pO2. High affinity. O2 loads
Respiring tissue: Low O2 conc. Low pO2. Low affinity. O2 unloads

Question 7

How is pO2 lowered in respiring tissue?

Answer 7

When the cells respire, they use up O2.

Question 8

Cooperative binding definition

Answer 8

Binding of one molecule affects the binding affinity of subsequent molecules.

Question 9

What is meant when by oxygen binding being cooperative?

Answer 9

When the 1st O2 molecule binds to the haemoglobin, the shape of the haemoglobin changes, causing the binding of the next few O2 molecules easier.
As it gets more saturated, it gets harder for more O2 molecules to join.

Question 10

What is meant by 100% and 0% saturation on a dissociation curve?

Answer 10

100% = Every haemoglobin carries a maximum of 4 O2 molecules.
0% = No haemoglobin molecules are carrying any O2.

Question 11

What do dissociation curves show?

Answer 11

How saturated the haemoglobin is with O2 at any given partial pressure.

Question 12

What factors affect the position of a dissociation curve?

Answer 12

• The organism’s environment (oxygen availability)
• How active/metabolically active the organism is (eg. activity, maintenance of a high body temperature etc)

Question 13

What will happen to the dissociation curve for an organism with less O2 available in their environment?

Answer 13

• Their haemoglobin will have a higher affinity for oxygen
• Shifting its O2 dissociation curve to the left

Question 14

What will happen to the dissociation curve for an organism with a higher metabolic rate?

Answer 14

• Their haemoglobin will have a LOWER affinity for O2 to allow it to supply the cells and tissues with sufficient oxygen to meet the energy demands
• Shifting its O2 dissociation curve to the right