module 3 - 8.4 transport of oxygen and carbon dioxide in the blood Flashcards
what does affinity mean?
tendency to bind to oxygen
what is the affinity of haemoglobin for oxygen?
high
at high partial pressures of oxygen, what happens to the haemoglobin?
it will bind to the oxygen forming oxyhaemoglobin
what happens to oxygen at high/ low concentration?
high conc. - oxygen binds to haemoglobin
low conc. - oxygen dissociates to haemoglobin
what is the equation for oxyhaemoglobin?
——————————affinity————————————->
Hb + 4O2 ⇌ Hb(O2)4
haemoglobin + oxygen ⇌ oxyhaemoglobin
<—————————dissociation———————————
what is partial pressure?
measuring concentration of gas when mixed with another gas
what is haemoglobins oxygen dissociation curve?
it is a sigmoid curve and plateau’s when all haemoglobin is oxyghaemoglobin
at respiring tissue or capillary beds, what is pO2?
low, so haemoglobin dissociates its oxygen to 20-25% saturation
what happens as oxygen binds to one monomer of Hb?
molecules shift from tense to relaxed state
what does the shift from tense to relaxed state promote?
promotes the binding of oxygen to remaining 3 monomer’s haem group thus saturating the Hb molecule with oxygen
what is cooperative binding?
the first oxygen molecule binds and changes structure of haemoglobin molecule, makes it easier for each successive oxygen molecule to bind
what happens when oxygen starts binding to the haemoglobin?
the alpha bonds start breaking
when does the dissociation from oxyghaemoglobin to haemoglobin occur?
doesn’t happen until capillaries
where is the highest concentration of oxygen?
lungs
where is oxygen concentration low?
in capillaries - its used for respiration
what is deoxygenated haemoglobin?
haemoglobin without the bound oxygen
how is the difference of absorption between oxy & deoxyhaemoglobin?
oxy - lower
deoxy - higher
measured with pulse oximeter
what is the Bohr effect?
- helps oxyhaemoglobin to dissociate and get oxygen more easily
- it describes how high pCO2 affects Hb’s affinity for oxygen
what does CO2 in the plasma form?
carbonic acid, this lowers pH of blood, causes oxyHb to dissociate its oxygen
what happens in respiring tissue? (to do with Bohr effect)
where pCO2 is high, Hb releases O2 more easily
what happens in the lungs? to do with Bohr effect)
- decrease in CO2 causes increase in blood pH (Hb releases O2 more easily)
- where pCO2 is low, Hb binds to oxygen more easily
where is CO2 the highest and what does this cause?
- highest in cells/respiring tissue
- diffuses down conc. gradient to lungs then to air
what molecules trigger the Bohr effect?
- carbon dioxide
- lactic acid
why does lactic acid trigger the Bohr effect?
- lactic acid is produced when cells don’t have enough oxygen
- this increases acidity of blood more than CO2
- cells need more oxygen
what produces carbonic acid?
when CO2 is dissolved in plasma
how do you know how strong the Bohr effect is?
steeper gradient, stronger Bohr effect
why do marine animals need to have a strong Bohr effect?
they need to dive down deep and allows for nearly all oxygen to dissociate and supply the body
where is fetal haemoglobin found?
red blood cells and is involved in transporting oxygen from mothers bloodstream to organs and tissues in foetus
fetal haemoglobin has a different composition from adult haemoglobin, what does this allow?
allows oxygen to bind more strongly, higher affinity for O2
- developing foetus is able to retrieve oxygen from mothers bloodstream
what does the structure and behaviour of lugworm enable for the organism?
to thrive in low-oxygen environment
what is the water flow like through the burrow when submerged by tide?
continuous
how does oxygen diffuse in a lugworm?
through the gills and body surface
what are the differences between human and lugworm haemoglobin?
- lugworm reaches a high saturation at much lower partial pressure to that of man
- dissociation curve is shifted to the left and lugworm has very high affinity for O2
- lugworm haemoglobin shows no Bohr shift
what is myoglobin?
an oxygen-binding protein found in skeletal muscle tissue of vertebrates and mammals
what is the difference in functions between haemoglobin and myoglobin?
haemoglobin - transports oxygen
myoglobin - store oxygen
what does high concentrations of myoglobin in muscle cells allow?
allows organisms to hold their breath for a longer period of time
- diving mammals have muscles with high abundance of myoglobin
what 3 ways can carbon dioxide be transported?
- dissolved in plasma as CO2
- combined with amino groups of haemoglobin to form CARBAMINOHAEMOGLOBIN
- converted to hydrogen carbonate ions (HCO3-) in cytoplasm of RBCs and then transported to plasma as HCO3-
what is the Haldane Effect?
- oxygenation of blood in the lungs displaces CO2 from haemoglobin which increases removal of carbon dioxide from blood
- this means oxygenated blood has a reduced affinity for carbon dioxide
where does most carbon dioxide diffuse into?
the cytoplasm of erythrocytes
what does carbonic anhydrase do?
converts carbon dioxide and water into carbonic acid which then dissociates into hydrogen carbonate and hydrogen ions
what is the chloride shift?
- HCO3- ions leave the erythrocytes and enter plasma by diffusion
- to maintain electrochemical balance, chloride ions are imported into erythrocytes
what is haemoglobonic acid?
- H+ producsed by dissociation of carbonic acid bind with haemoglobin in RBCs - this forms heamoglobonic acid
- haemoglobin acts as a buffer to maintain blood pH
