Transport of oxygen + carbon dioxide

Describe structure of the haemoglobin molecule

-made up of 4 polypeptide chains so 4 haem groups

-each haem group has Fe 2+ ion so 4 oxygen molecules bind to 1 haemoglobin molecule

What is cooperative binding?

when 1st oxygen molecule binds to haemoglobin it changes it's shape making it easier for 2nd to attach

What happens when third oxygen molecule binds to haemoglobin?

doesn't change haemoglobin's shape so takes larger partial pressure for 4th one to bind

Partial Pressure

pressure a gas would exert if it was the only one present

Affinity

degree of attraction of 2 molecules

How is saturation of haemoglobin with oxygen affect by oxygen's partial pressure?

-at low PP the sat is also low due to affinity reducing and oxygen being readily released

-at high PP the sat is also high due to affinity increasing as oxygen isn't being released by oxyhaemoglobin

Why is the dissociation curve of foetal haemoglobin moved to the left?

-foetal haemoglobin has a higher affinity than adult so % saturation is also higher

-haemoglobin of foetus differs by 2 polypeptide chains

What are the effects on CO2 concentration on the dissociation curve?

-Bohr effect = moves curve to the right

-high CO2 conc = low haemoglobin affinity so oxygen is released more readily

Describe oxygen transport in lungworm

-lives in low O2 environment

so haemoglobin loads oxygen readily but only releases when PP of oxygen is low

Describe oxygen transport in llama

-live in increased altitude so haemoglobin affinity is higher at all PP

-readily loads oxygen and releases when PP is low

Describe the chloride shift

• CO2 diffuses in red blood cell

• carbonic anhydrase catalyses CO2 + H2O —> H2CO3

• carbonic acid dissociates into H+ + HCO3- (diffuse out)

• Cl- FC diffuses into RBC to maintain electrochemical neutrality + balance outflow of negative ions

• H+ cause oxyhaemoglobin to dissociate into O2 + haemoglobin so reduces affinity for oxygen = Bohr effect

What happens at arterial end of capillary?

• hydrostatic pressure > osmotic pressure due to heart pumping

• water + small molecules forced through capillary walls = tissue fluid

• large molecules stay in blood to lower wp

What happens at venule end of capillary?

• osmotic pressure > hydrostatic pressure due to reduced volume + friction of walls

• water moves into blood by osmosis down wp gradient

• excess tissue fluid returned to blood via lymph vessels