8.4 Flashcards
how are erythrocytes specialised to carry oxygen?
they have a biconcave disk shape which gives a larger surface area for diffusion
no nucleus or organelles to maximise haemoglobin storage
haemoglobin + oxygen
oxyhaemoglobin
what is positive cooperativity?
when oxygen binds to one haem group, the shape of haemoglobin changes to make it easier for another oxygen to bind
why do oxygen dissociation curves have an s shape?
because of positive cooperativity making it easier to gain or lose oxygen when one has binded to a haem group
what affinity does haemoglobin have for oxygen at high p(O2)?
high affinity
what affinity does haemoglobin have for oxygen at low p(O2)?
low affinity
what is the Bohr effect?
at high p(CO2), haemoglobin gives up oxygen more easily
why is the Bohr effect important when exercising?
at high p(CO2) in respiring cells, O2 can be released and used in aerobic respiration to provide ATP
CO2 can be removed by haemoglobin which prevents toxic build up
what affinity does haemoglobin have for oxygen at high p(CO2)?
low affinity
what affinity does haemoglobin have for oxygen at low p(CO2)?
high affinity
what is the change in the graph for Bohr effect?
shifts to the right
what is different about fetal haemoglobin?
fetal haemoglobin has a higher affinity for oxygen
this allows for oxygen to be transferred to the placenta from the maternal blood more easily
what is the change in the graph for fetal haemoglobin?
shifts to the left left
what happens to CO2 when it enters the erythrocyte?
it reacts with water to form carbonic acid (H2CO3)
which enzyme catalyses the production of carbonic acid?
carbonic anhydrase
what does carbonic acid dissociate into?
HCO3- ions
H+ ions
what do the HCO3- ions do?
they diffuse out of the erythrocyte down the concentration gradient
what is caused by HCO3- ions diffusing out?
a change in the electrochemical gradient as it becomes more positive
what restores the electrochemical gradient?
Cl- ions move into the erythrocyte
what is the movement of Cl- into the erythrocyte called?
chloride shift
how does a high p(CO2) cause oxygen to be released by haemoglobin?
oxygen stored as oxyhaemoglobin
CO2 reacts with water to form carbonic acid
carbonic acid dissociates into HCO3- and H+
H+ ions causes oxyhaemoglobin to release oxygen and react to form haemoglobonic acid
how do erythrocytes maintain a steep concentration gradient to take in more CO2?
by converting CO2 into carbonic acid, it reduces the CO2 concentration inside the erythrocyte while the respiring tissues will have a high CO2 concentration from respiration
CO2 moves into erythrocyte down the conc gradient
when does carbonic anhydrase catalyse the reverse reaction?
when there is a low concentration of CO2 like in the lungs
how does CO2 leave the erythrocyte?
carbonic acid is broken down into CO2 and water which increases the CO2 concentration gradient in the erythrocyte
CO2 then moves down the concentration gradient, out of the erythrocyte and into the lungs
how does haemoglobin act as a buffer?
when acid is added it accepts H+ ions to form haemoglobonic acid which raises the pH back to normal
how does CO2 reduce Hb’s affinity for O2?
reacts with water to form carbonic acid
carbonic acid dissociates into H+ ions
H+ ions react with Hb to form haemoglobonic acid which prevents oxygen binding
