3.4-Mass transport in animals 2

where in the body is o2 conc. high and where is it low?

high- alveoli of the lungs

low- respiring cells and tissues

what does conjugated and quarternary mean? (both used to describe Hb)

conjugated- protein is bound to a non protein group

quarternary- further folding of more than one polypeptide chain

how many polypeptide chains are there in haemoglobin and how many o2 molecules can one haemoglobin carry?

4 polypetide chains and it can carry 4 o2

what is the function of the haem group?

binds to o2 to form oxyhaemoglobin

what is co-operative binding?

each haemoglobin molecule combines with 4 o2 molecules

binding of the first haem group with an o2 molecule changes the tertiary structure + shape of the haemoglobin molecule

this uncovers the second haem group, making it more accessible and easier for o2 to bind, increasing the affinity

increases affinity of the 3rd haem group

explains why oxygen disassociation curve has sigmoidal shape

what is the Bohr shift and what is its significance?

increase in temp, acidity and co2 conc. displaces curve to the right

facilitates delivery of o2 to respiring tissuess

when is it likely there’ll be an increase in temp, acidity and co2 conc. of muscle?

during exercise- faster cellular respiration

more heat and co2 produced

co2 dissolves to make weak acid (carbonic acid) so pH decreases

how does Bohr shift affect haemoglobin’s affinity for o2?

lowered affinity- can easily unload more o2

less saturated with o2 at any given pO2

since it Bohr shift occurs during exercise, more o2 is needed and so it can be easily unloaded at the respiring tissues where there’ll be low o2 conc

what does it mean if a disassociation curve is displaced to the right?

affinity of Hb for o2 is decreased

unloading/delivery of o2 to the tissues is increased

there is a lower saturation of Hb with o2 at any given partial pressure

what does it mean if the disassociation curve is displaced to the left?

affinity of Hb for o2 is increased

unloading/delivery- decreased (i.e loading increased)

there is a higher saturation of Hb with O2 at any given partial pressure

what happens at high pO2?

occurs in the alveoli of the lungs

Hb has high affinity for O2- they are able to bind more easily

almost 100% saturation

what happens at low pO2?

occurs in the respiring tissues

Hb has a low affinity for O2- releases O2 more easily

lower saturation

lugworm Hb has a very high affinity for O2. what does this mean and why is it an advantage?

easier for Hb to bind to o2 at low pO2- reaches high saturation at lower pO2

easily meets respiratory needs as O2 conc in burrow falls to very low levels at low tide

what does the low affinity of shrew Hb for O2 ensure?

O2 is unloaded/delivered rapidly to the tissues

lowered affinity isn’t a disadvantage when loading o2, as full saturation is readily achieved in atmospheric air

why do smaller mammals have Hb with a lower affinity for o2? (mention sa:v and metabolic rate)

to facilitate oxygen delivery to the tissues

larger sa:v- lose heat faster

increased respiration rates to generate heat to replace what is lost

higher rate of o2 consumption- higher metabolic rate

what does high affinity Hb mean?

usually in organisms that live in low pO2 environments e.g high altitudes

Hb loads o2 more readily in lungs

curve shifts left

Hb more saturated at any given pO2

What does low affinity Hb mean?

usually in organisms that have high metabolic rate (e.g small mammals with large sa:v ratio, + high rates of heat loss)

Hb unloads/releases o2 more readily at tissues for respiratio

curve shifts right

Hb reduced saturation at any pO2