Haemoglobin

Question 1

what is haemoglobin?

Answer 1

a quaternary protein

Question 2

describe the structure of haemoglobin (3)

Answer 2

• four polypeptide chains
• the haem group contains an iron ion
• haemoglobin has four iron ions in total

Question 3

which part of haemoglobin specifically does oxygen bind to?

so how many oxygen molecules can bind to one haemoglobin?

Answer 3

the iron ions

four

Question 4

when oxygen combines with haemoglobin, the substance formed is called ____________________

Answer 4

oxyhaemoglobin

Question 5

what shape is an oxygen dissociation curve?

Answer 5

an ‘S’ shape; described as a ‘sigmoid curve’

Question 6

why is the oxygen dissociation curve ‘S’ shaped? (4)

Answer 6

• first oxygen molecule combines relatively slowly with the first iron ion
• but this initial binding of oxygen causes the tertiary structure of haemoglobin to change
• change in the tertiary structure = exposure of the rest of the oxygen binding site
• it is now easier for the other oxygen molecules to bind to their iron ions

Question 7

relationship of oxygen and haemoglobin at the lungs

Answer 7

• partial pressure of oxygen is high
• haemoglobin has a high affinity for oxygen at a high pressure of oxygen
• association occurs

Question 8

relationship of oxygen an haemoglobin at the tissues

Answer 8

• low partial pressure of oxygen
• haemoglobin has a low affinity for oxygen at a low pressure of oxygen
• dissociation occurs

Question 9

high ppO2 =

Answer 9

increased affinity
increased association

Question 10

low ppO2 =

Answer 10

decreased affinity
increased dissociation

Question 11

what else can cause increased dissociation?

Answer 11

a high carbon dioxide concentration

• lowers haemoglobin’s affinity for oxygen
• causes a shift to the right (bohr shift)

Question 12

what are the factors that may impact the type of haemoglobin an organism possesses? (3)

Answer 12

• where they live
• how active they are
• their size

Question 13

haemoglobin adapted for low oxygen environments (2)

Answer 13

• organisms in a low oxygen environment will have haemoglobin with a higher affinity for oxygen
• this means that their dissociation curve will shift to the left

Question 14

haemoglobin adapted for high activity levels (2)

Answer 14

• organisms with high activity levels will have haemoglobin with a lower affinity for oxygen
• this means their dissociation curve will shift to the right