Haemoglobin - A6 Flashcards
Where is haemoglobin found?
It is found in red blood cells
What is the role of haemoglobin?
To carry oxygen
What is the structure of haemoglobin?
Hb is a large protein(quaternary) made up of 4 polypeptide chains
What is the structure of the polypeptide chains?
Each chain contains 1 haem group, containing iron - therefore each haemoglobin can carry 4 oxygen atoms
How does oxyhaemoglobin form?
-In the lungs, oxygen associates/loads(bonds/joins) to Hb in RBCs to form oxyhaemoglobin in the lungs
-This is reversible as near body cells, oxygen disassociates/unloads(leaves) and oxyhaemoglobin is converted back into haemoglobin at respiring tissue
What does haemoglobin have an affinity for?
-Hb has an affinity for oxygen ->Hb has a tendency to bind to O2
-Hb’s affinity varies depending on the condition it’s in
What is partial pressure of oxygen?
-pO2 is just a measure of oxygen conc. - the greater the conc. of oxygen, the higher the partial pressure.
-partial pressure of oxygen is one of the conditions that affects Hb’s affinity for O2
Does oxygen load onto haemoglobin when there’s a high or low partial pressure?
It loads when theres a high partial pressure and unloads when there’s a low partial pressure.
When the partial pressure is high, does the oxygen load/ unload, and what is the affinity like?
partial pressure - high
affinity - high
loads
When the partial pressure is low, does the oxygen load/unload, and what is the affinity like?
partial pressure - low
affinity - low
unloads
What does an oxygen disassociation curve show?
It shows how saturated the haemoglobin is at any given partial pressure
How does saturation effect haemoglobin’s affinity for oxygen?
(sigmoidal curve and cooperative binding)
-When Hb binds to the first molecule of O2, the tertiary structure of the Hb alters, which uncovers another binding site, making it easier for other O2 molecules to bind.
-Then as the Hb becomes more saturated it becomes harder for O2 to bind.
-This causes the steep section in the middle of the graph where it’s really easy for the O2 to bind.
How does the partial pressure of carbon dioxide affect the affinity?
-At high pCO2, Hb had a lower affinity for O2 and unloads more readily.
-At high pCO2 causes a shift of the disassociation line to the right, known as the Bohr effect
-This is good because there is usually a high pCO2 near aerobically respiring cells which need more O2
-at higher pCO2, the haemoglobin has a lower affinity for oxygen at the same pO2, therefore oxygen unloads more readily to respiring tissue to be used for aerobic respiration
Why does a high pCO2 create a lower affinity for oxygen?
-CO2 diffuses into blood and becomes carbonic acid
-this makes the blood more acidic(because carbonic acid disassociates and releases H+)
-This alters(the hydrogen bonding in)the secondary and tertiary structures of haemoglobin
-reducing haemoglobin’s affinity for oxygen=increased unloading at the same pO2
Why are there different types of haemoglobin?
-Different types of haemoglobin, in different organisms, have different oxygen transporting capacities
-this depends on: where the organism lives, how active the animal is, how big the animal is
