Haemoglobin Flashcards
How do organisms carry oxygen to their cells?
in the blood via haemoglobin
What is special about haemoglobin?
it can have many variations for different organisms to fit their environments
Why don’t red blood cells have a nucleus?
to leave space for haemoglobin
What is haemoglobin?
a globular protein made up of 4 polypeptide chains
What level of structure does haemoglobin have?
a quaternary structure
What are the chains at the top of haemoglobin called?
alpha chains
What are the chains at the bottom of the haemoglobin called?
beta chains
What does a fully saturated haemoglobin have?
all 4 oxygen molecules bound to the haem groups
What does a high oxygen affinity mean?
it wants to/has a tendency to bind to O2
What is pO2? (i.e in the alveoli)
partial pressure of oxygen (how much oxygen there is)
What is partial pressure measured in?
kPa
What happens at the gas exchange surfaces (at the alveoli) with haemoglobin?
haemoglobin has a high affinity for O2, so the O2 binds readily
What happens at the respiring tissues with haemoglobin?
haemoglobin has a low affinity for O2, as the high concentration of CO2 causes the haemoglobin to change shape, which releases the oxygen
What shape is the oxygen dissociation curve?
S-shaped
Why is the oxygen dissociated curve shaped in this way? Explain each region of it
initial slow increase of pO2 as it is slightly more difficult for the first molecule of O2 to bind to the Hb
then pO2 increases quickly as after the first O2 has bound it slightly distorts the Hb protein which makes it much easier for the second and third O2 to bind
finally pO2 slows down again as it is more difficult for the fourth O2 to bind
What happens to Co2 levels when the rate of aerobic respiration increases, and what does this mean?
the CO2 levels go up, and this CO2 dissolves to form carbonic acid
What does carbonic acid do to the haemoglobin?
carbonic acid changes the blood pH and this affects the haemoglobin; they lose oxygen more readily- this shifts the oxygen dissociation curve to the RIGHT
What is the Bohr effect and why is it a good thing during exercise?
-haemoglobin gives up it’s oxygen more readily at a higher pCO2
-during activity there is a higher respiratory rate which increases the production of CO2- this leads to increased carbonic acid levels in blood which lowers the blood pH- this means that haemoglobin more readily gives up it’s oxygen which is an an advantage during exercise as your cells need more oxygen
Which way does the Bohr effect shift the oxygen dissociation curve?
TO THE RIGHT
What factors result in the Bohr effect?
-blood temperature
-blood pH
-CO2 concentration
Why do different animals have variation in their haemoglobin?
to fit their habitats- they have different sequences of amino acids
What is myoglobin?
a molecule with a similar structure to haemoglobin but only has 1 haem group instead of 4; it also has a very very high affinity for oxygen even at very low pO2
What is the myoglobin oxygen dissociation curve like compared to the haemoglobin oxygen dissociation curve?
it looks like an inverted L shape as it stays saturated for longer with a very steep decrease/increase
What type of mammals generally have more myoglobin?
diving mammals
When does the oxymyoglobin dissociate?
when the oxygen levels are very low
Where is myoglobin found?
myoglobin is found in muscle cells where it acts as an oxygen reserve (good oxygen storage)
Why does foetal haemoglobin have a higher oxygen affinity than the mothers haemoglobin?
the mother is using some of her own haemoglobin which means for the foetus there is less, so it’s haemoglobin needs to get fully saturated in a lower pO2, so foetus haemoglobin has a higher affinity for oxygen
If the oxygen dissociation curve is to the left, what does this mean about the Hb?
the haemoglobin is more easily saturated with oxygen
If the oxygen dissociation curve is to the right, what does this mean about the Hb?
the haemoglobin more readily releases oxygen to tissues
Why do lugworms have haemoglobin that has a high affinity for oxygen?
because they live in burrows beneath sand where there’s a low oxygen concentration
Why do mice have haemoglobin that has a lower affinity to oxygen?
because they have a larger surface area to volume ratio than a human-they lose heat quickly so have a high metabolic demand so need to be able to unload oxygen easily to meet oxygen demand
Why is having more red blood cells an advantage at higher altitudes?
-at higher altitudes there is a lower partial pressure of oxygen
-more red blood cells mean more haemoglobin
-so more haemoglobin can bind more oxygen for use in respiration
