transporting oxgen Flashcards
what is haemoglobin
gobular protein found inside red blood cells
how is oxyhaemoglobin formed
iron ion reversibly combing with one oxygen molecule
haem group has hight affinity for oxygen, each can hold one oxygen molecule, each haemoglobin molecule can combine with 4 oxygen molecule
oxygen binds reversibly to haemoglobin to produce oxyhaemoglobin (Hb(O2)4
structure of haemoglobin
made of 4 polypeptide chains, each bound to 1 haem prosthetic group
what is oxygen saturation
measure of percentage of oxyhaemoglobin in blood
how is oxygen concentration measured
relative pressure that it contributes to a mixture of gases
how can haemoglobin’s oxygen affinity vary
depending on oxygen tension
how can oxygen tension vary
oxygen binds to haemoglobin when oxygen is at high concentration
high oxygen tension –> high affinity
oxygen dissociates from haemoglobin when oxygen is at low concentration
low oxygen tension –> low affinity
why does Hb has low affinity for oxygen at low oxygen tension
haem groups that attract oxygen are in centre of Hb, diffusion distance is quite long
why does the binding of one oxygen molecule to Hb cause a conformational change
makes it easier for excessive oxygen molecules to join
positive cooperatively/cooperative binding
how does O2 dissociate
blood reaches body tissue
oxygen tension in body cells cytoplasm is lower than in erythrocyte –> oxygen diffuse out of erythrocyte
once first oxygen molecule dissociate, haemoglobin molecule changes shape, becomes easier to remove remaining oxygen
factors affecting oxygen affinity
physical
chemical [temp, pH(increase in CO2, reduce pH)]
effect of carbon dioxide on oxygen affinity
lower the pH, lower the Hb’s affinity for oxygen, increases release of oxygen from Hb
what is the Bohr shift
effect of high CO2 concentration on Hb’s affinity for oxygen
effect of temperature on oxygen affinity
decrease in temp, increases Hb’s oxygen affinity, hypothermia reduces the blood’s ability to release oxygen into metabolising tissue
how is foetal haemoglobin different from adult haemoglobin
higher affinity for oxygen, to maximise oxygen uptake from mother’s bloodstream, allows foetus to obtain oxygen from placenta
how is oxygen affinity for myoglobin different from haemoglobin
very high, even at low partial pressure, oxymyoglobin will only dissociate when oxygen levels are low
