Haemoglobin Flashcards
(32 cards)
What percentage of the dry mass of a red blood cell does haemoglobin make up
95%
What is haemoglobin made up of
four polypeptide chains (2α and 2β), each bound to one haem group.
How many oxygen molecules can each haem group within haemoglobin make up
One oxygen molecule
How many oxygen molecules can one haemoglobin molecule bind to
4 - forms oxyhaemoglobin (Important to know name)
Where does haemoglobin load/associate (bind) with oxygen?
The lungs
Where does haemoglobin unload/dissociate (release) oxygen
In tissues
What do haemoglobins with a higher affinity (chemical attraction) do
Take up more oxygen
What do haemoglobins with a lower affinity do
take up oxygen less readily
Where is haemoglobins oxygen affinity highest
In lower carbon dioxide partial pressures (lungs)
Where is haemoglobins oxygen affinity lowest
In higher carbon dioxide partial pressures. (muscles)
What is oxygen carried as
oxy-haemoglobin
What is carbon dioxide carried as
carbaminohaemoglobin
What region of the body is haemoglobins affinity to oxygen high
Gas exchange surfaces (High oxygen concentrations, low CO2 concentrations). So oxygen is attached
What region of the body is haemoglobins affinity to oxygen low
Respiring Tissues (Low oxygen concentration, high CO2 concentration). So oxygen is released.
How can the concentration of a gas in a mixture of gases can be quantified
in terms of its partial pressure (Measured in kPa and written as P(O2), P(CO2), greater the concentration - higher the partial pressure)
Why is oxygen disassociation curve shallow at first
haemoglobin sub units are closely united making it difficult for the first oxygen molecule to bind to one of the 4 sites.
What causes the steep increase in affinity in the oxygen disassociation curve
binding the first oxygen alters the quaternary structure of haemoglobin making it easier for the other sub units to bind to an oxygen molecule (conformational change). Binding the first molecule makes it easier for the second, this is called POSITIVE COOPERATIVITY.
What causes the graph to flatten off in the oxygen disassociation curve
due to probability alone it is more difficult for the final oxygen molecule to bind as most sites are bound already.
What is step 1 of haemoglobin loading and unloading oxygen in the blood
Oxygen loads onto haemoglobin at high partial pressure. e.g. in lungs.
In the lungs haemoglobin has a high affinity for oxygen.
What is step 2 of haemoglobin loading and unloading oxygen in the blood
Tissues have a low partial pressure of oxygen as it has been used in respiration.
In tissues haemoglobin has a lower affinity for oxygen.
What is step 3 of haemoglobin loading and unloading oxygen in the blood
Haemoglobin unloads oxygen at low partial pressure.
Explain step 1 of the Bohr effect
Carbon dioxide removed from the exchange surface (lungs).
This raises the pH as the carbon dioxide concentration has lowered.
This alters the shape of haemoglobin so it loads oxygen more readily.
Explain step 2 of the Bohr effect
In respiring tissue pH lowers as carbon dioxide is released by respiring tissues as a by-product
This alters the shape of haemoglobin making it have a lower affinity for oxygen and unloads oxygen into respiring cells easily.
What determines a haemoglobin molecules oxygen binding properties
The tertiary and quaternary structure of the globular haemoglobin molecule (determined by amino acid sequence)
