⭐️Exchange: Haemoglobin Flashcards
What is haemoglobin made of?
A quaternary protein molecule made of 4 polypeptides (two of which are alpha polypeptides and 2 are beta polypeptides) where each one is associated with a haem group which contains an Fe2+ ion.
Where do oxygen molecules mind on a heamoglobin?
The bind to the Fe2+ of each polypeptide so each haemoglobin molecule can carry for O2 molecules
What is affinity?
The degree to which a substance tends to bind with another
What is loading and where does it occur?
The process of haemoglobin binding with oxygen and it takes place in the lungs
What is unloading and where does it occur?
The process of haemoglobin releasing oxygen and it occurs in the tissues
Give two things haemoglobin must do to be efficient in carrying out its role in transporting oxygen. How is it able to do these both?
- readily associating with oxygen at the surface where gas exchange takes place
- readily dissociating from oxygen at the tissues that require it
By changing its affinity for oxygen under different conditions
How is haemoglobin able to change its affinity under different conditions? Give an example
As it’s shape is able to change in the presence of certain substances. For example, in the presence of carbon dioxide, the new shape of the haemoglobin molecule binds more loosely to oxygen which as a result causes the haemoglobin to release the oxygen
Where is the affinity of haemoglobin high and where is it low?
High at gas exchange surfaces and low in respiring tissue
Why do different haemoglobin molecules (from different organisms) have different affinities of oxygen?
Because each species produces a haemoglobin with a slightly different amino acid sequence so they each have different tertiary and quaternary structures and so different binding properties. Depending on its structure haemoglobin moelcules range from those with a high affinity for oxygen and those with a low affinity fro oxygen
In the oxygen dissociation curve, why is the gradient of the curve initially shallow?
Because the shape of the Hb molecule makes it hard for the first Hb molecule to bind to one of the four sites because they are closely united so at low oxygen concentrations little oxygen binds
In the oxygen dissociation curve, why does the graph steepen?
Because the binding o the first molecule changes the quaternary structure of the haemoglobin molecule causing its shape to change which makes it easier for other subunits to bind to an oxygen molecule.
What is positive cooperativity in Hb?
Where it takes a smaller partial pressure of oxygen to bind the second molecule than it did the first one so as more oxygen binds, affinity increases
In the oxygen dissociation curve, why does the graph plateau?
Because by now, the majority of binding sites are occupied so it’s less likely that a single oxygen molecule will find an empty site to bind to
In the oxygen dissociation curve, what does it mean if:
- the graph is shifted to the left?
- the graph is shifted to the right?
- There is a greater affinity of Hb for oxygen so it loads oxygen readily but it unloads it less easily
- there is a lower affinity of Hb for oxygen so it loads oxygen less readily but it unloads it more easily
What is bohr’s affect?
The fact that the greater the concentration of carbon dioxide, the more readily the Hb releases its oxygen