TOPIC 3 - Mass transport - Hb

Question 1

describe the structure of haemoglobin?

Answer 1

• globular protein
• 4 polypeptide chains w quaternary structure each carrying a haem group
  haem group = contains iron ion
  red in colour

Question 2

describe the role of haemoglobin?

Answer 2

present in red blood cells
oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues.

Question 3

name 3 factors affecting oxygen-haemoglobin binding?

Answer 3

• partial pressure/conc of O2
• partial pressure/conc of CO2
• saturation of haemoglobin with oxygen

Question 4

how does the pressure of oxygen affect oxygen-haemoglobin binding?

Answer 4

As partial pressure of O2 increases = haemoglobin has high affinity for oxygen. i.e will readily combine with oxygen = so HIGH SATURATION of O2

when Partial pressure is low = Hb has low affinity for oxygen = releases oxygen easily rather than combine

Question 5

How does partial pressure of carbon dioxide affect oxygen-haemoglobin binding? what is the bohr effect?

Answer 5

increased PCO2 = decreases affinity of Hb for oxygen = increases rate of oxygen unloading

• conditions becomes acidic causing Hb to change shape

Question 6

How does saturation of Hb with oxygen affect oxygen-haemoglobin binding?

Answer 6

it is hard for the first oxygen molecule to bind. once it has binded to the Hb, the Hb changes shape to make it easier for the 2nd, 3rd Oxygen to bind. = Positive cooperativity

It is then harder for the 4th oxygen molecule to bind because there is a low chance of finding a binding site.

Question 7

explain why oxygen binds to Haemoglobin in the lungs?

Answer 7

• partial pressure of oxygen is high
• low concentration of CO2 in the lungs, so affinity is high
• there is positive cooperativity

Question 8

explain why oxygen is released from Haemoglobin in respiring tissues?

Answer 8

• partial pressure of oxygen is low
• high concentration of CO2 in respiring tissues, so affinity decreases

Question 9

what do oxy-haemoglobin dissociation curves show?

Answer 9

saturation of Hb w O2 (%) against partial pressure of oxygen (KPa). curves further to the left show that Hb has a higher affinity for oxygen.

Question 10

How does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?

Answer 10

curves shift to the right because Hb affinity for oxygen has decreased

Question 11

what is the affinity of Hb for oxygen for organisms living in environments with a low conc of oxygen?

Answer 11

• they have Hb with higher affinity for O2 than human Hb
• dissociation curve is to the left of ours