haemoglobin Flashcards
what does haemoglobin do?
● loads O2 (at lungs to form oxyhaemoglobin)
● oxyhaemoglobin carries O2 to respiring cells
● unloads O2 at respiring cells (reforms haemoglobin)
● quaternary protein with associated iron (Fe2+) containing haem groups
● protein found in rbc
explain lungs / alveoli
● PALS
● high ppO2 (high conc of oxygen)
● high affinity (more likely to be loading O2)
● loading
● saturated (more O2 molecules loaded)
explain respiring cells
● PALS
● low ppO2 (low conc of oxygen)
● low affinity for O2
● unloading
● less saturated
what is the shape of the ODC?
sigmoidal curve
what does the steep part of the ODC mean?
● going up - deoxygenated blood - O2 is being loaded
● going down - oxygenated blood - O2 is being unloaded
what is cooperative bonding?
● loading of first oxygen changes tertiary structure of haemoglobin
● exposes second haeme group binding site
● increases affinity of haemoglobin - second O2
● loads more readily
● reason why ODC is a sigmoidal curve
what is the bohr shift?
● changes in oxygen dissociation curve as a result of carbon dioxide levels
● in the presence of CO2, Hb has a lower affinity for O2
● so dissociates from haemoglobin more readily
● by decreasing blood pH
● the saturation of Hb decreases
● O2 is more readily available to respiring cells
how does pCO2 affect affinity for Hb loading / unloading?
● at high pCO2, Hb unloads more readily
● good as usually high CO2 near respiring cells which need more O2
● a high pCO2 causes a shift of the odc to the right - known as the bohr shift
explain haemoglobin affinity for O2 at different partial pressures
● at same ppO2 haem = more saturated
higher affinity for O2 at any ppO2
e.g. lugworm:
in low ppO2 environment
needs to have high affinity
haemoglobin loads more readily
left shifted
● at same ppO2 haem = less saturated
lower affinity for oxygen at any partial pressure
(right shifted)
● e.g. hummingbird:
lots of muscular contractions
so needs lots of ATP
from aerobic respiration
oxyhaemoglobin unloads more readily
more oxygen to respiring cells
higher rate of respiration
● e.g. field mouse:
high metabolic rate
due to high SA:V ratio
meaning heat lost at a higher rate
heat replaced during respiration (exothermic)
oxyhaemoglobin unloads more readily
more oxygen to respiring cells
higher rate of respiration
what is a quaternary protein?
more than 1 polypeptide chain
what is the formula for percentage saturation?
oxygenated haemoglobin / maximum saturation x 100
