4.5 Transport of Gases in Blood Flashcards
describe the structure of erythrocytes and how it is adapted for gas exchange
biconcave shape - maximises surface area for gas exchange
small + flexible - allows easier movement through narrow capillaries
no nucleus - more room to carry respiratory gases
packing with haemoglobin
what is haemoglobin made up of?
4 globular proteins
1 iron ion
give a property of haemoglobin
it has an affinity for oxygen - can carry up to four oxygen molecules
what is it called when haemoglobin becomes oxygenated?
give the equation
oxyhaemoglobin
Hb + 4O2 « Hb4O2
define partial pressure of a gas
amount of gas present in a mixture
measured by the pressure it contributes to total pressure of gases
describe how oxygen is transported in the lungs
oxygen diffuses into blood plasma
passes down a concentration gradient + into erythrocytes
oxygen binds to Hb to maintain the conc gradient
oxygen binds to Fe2+ group of Hb
describe how oxygen is transported in the respiring tissue
oxygen dissociates from oxyhaemoglobin
oxygen can then diffuse out of the erythrocytes + to respiring cells
what is pO2?
partial pressure for oxygen
amount of oxygen in tissue
measured in kPa
what does it mean to have a high partial pressure for oxygen?
more oxygen molecules are able to associate with Hb molecules to be transported
where is haemoglobin saturation the highest in the body?
in the lungs
in respiring tissue, tje pO2 is low. what happens?
at low pO2, oxygen dissociates from oxyhaemoglobin + can diffuse to the respiring cells
as pO2 increases, what happens to the saturation of Hb?
increases
describe the process of oxygen associating with haemoglobin
after the first oxygen associates, the conformation of Hb changes
conformation change makes it easier for the 2nd and 3rd molecule to associate
it is difficult to associate a fourth oxygen because Hb becomes saturated (“full”)
what do we mean by high affinity?
Hb binds more easily, even at low pO2
dissociates less readily
what do we mean by low affinity?
Hb binds less readily
dissociates faster
oxygen is readily available for respiring tissue
what is foetal haemoglobin?
red blood cells in the foetus contain a special form of Hb
which has a high affinity for oxygen, adult or foetal Hb? explain why.
foetal Hb - helps to maimise oxygen uptake from mother’s blood, which has already lost some of its oxygen by the time it reaches placenta
to get oxygen from maternal blood to foetal blood, what must happen ?
foetal Hb needs a stronger affinity for oxygen than maternal Hb
give two features of foetal Hb
stronger oxygen affinity
becomes saturated at lower pO2
describe what myglobin is
respiratory pigment found in muscles
small red protein
contains haem group which binds to oxygen
give 3 features of myoglobin
higher affinity for oxygen than haemoglobin
becomes easily saturated with oxygen
not affected by pO2 in tissues
what happens when myoglobin binds to an oxygen molecule?
it does not give up easily so acts as an oxygen store
when o2 levels in active muscles get low, and co2 levels are high, myoglobin releases its store of o2
give differences in structure and affinity to o2 of haemoglobin and myoglobin
Hb-
tetramer- 4 polypeptide chains
supplies blood all over body
low affinity to o2 compared to Mb
Mb-
monomer- 1 polypeptide chain
supplies o2 to muscles
higher affinity to o2 compared to Hb
what is the Bohr effect?
effect of co2 on oxygen dissociation on Hb curve
at high carbon dioxide levels in tissues
Hb binds with O2 less well (low affinity) so releases more o2
at low carbon dioxide levels in lungs
Hb binds with oxygen more easily (high affinity)
