Haemoglobin 3.3.4 Flashcards
Describe the structure of the haemoglobin molecule
Quaternary structure in which all four polypeptides are linked together to form an almost spherical molecule. Each polypeptide is associated with a harem group which contains ferrous (fe2+) ions. Each fe2+ ion can combine with a single oxygen molecule (O2) making a total of four O2 molecules that can be carried by a single haemoglobin molecule in humans
What is haemoglobin
Protein molecules with a quaternary structure that has evolved to make it efficient at losing oxygen under one set of conditions and unloading under a different set
What is loading oxygen
The process by which haemoglobin binds with oxygen
Takes place in the lungs
What is unloading oxygen
The process by which haemoglobin releases oxygen
Takes place in respiring tissue \
What does it mean when haemoglobin has a high affinity for oxygen
Haemoglobin with a high affinity for oxygen takes up oxygen more easily but releases it less easily
What does it mean when haemoglobin has a low affinity for oxygen
Takes up oxygen less easily but releases it more easily
What is oxyhemoglobin
Once oxygen has bound to haemoglobin it is called oxyhaemoglobin
He+4O2<=>Hb(O2)4
What does it mean when haemoglobin is saturated with oxygen
When haemoglobin is holding maximum amount of oxygen it can combine to
What is cooperative binding
Cooperative nature of oxygen binding to haemoglobin, changing the shape when the first oxygen binds making it easier for further oxygen molecules to bind
Step by step of loading and unloading oxygen
Only at high concentrations can the first molecule bind. This causes a slight conformational change in the quaternary structure of the haemoglobin. The change in shape makes it easier for the next two oxygen molecules to bind (requires a lower partial pressure). This is called positive cooperative binding. Once the second and third oxygen molecules bind it is far more difficult for the final molecule to bind. This is because three of the binding sites are occupied and there is a lower probability that an oxygen molecule will encounter the empty site.
What is positive cooperativity
When the first oxygen attaches to a haem group and causes a conformational change
Hat is the Bohr effect
-When CO2 concentration causes the oxyhemoglobin curve to shift right
-Haemoglobin affinity for oxygen decreases because o the acidic conditions caused by CO2 dissolving in the blood forming carbonic acid
-This causes oxyhemoglobin to change shape slightly and releases oxygen
Foetal Haemoglobin
-foetal Otis supplied by the mothers blood in the placenta which means that there is a lower O2 concentration
-foetal Haemoglobin has a higher affinity for O2 at the same partial pressure of oxygen as adult Haemoglobin
-left shift
High altitude animal Haemoglobin
-lower partial pressure of oxygen
-Haemoglobin has a higher affinity for oxygen at a lower partial pressure of oxygen
-left shift
Active animal Haemoglobin (eg doves)
-doves have a faster metabolism and lots of muscle contractions when flying so require more oxygen for aerobic respiration
-Haemoglobin decreases affinity for oxygen and is more likely to unload at the same partial pressure of oxygen
-right shift
