oxygen transport

what type of protein is haemoglobin

quaternary protein

what is a quaternary protein

a protein consisting of four polypeptide chains

in haemoglobin, what are the four polypeptide chains composed of?

2 alpha globin chains and 2 beta globin chains

what is a prosthetic group in haemoglobin

where each polypeptide chain contains a haem group, which includes an iron (Fe2+) ion that binds to oxygen

haemoglobin is a globular protein. how does this help its function?

haemoglobin is water-soluble, allowing it to dissolve in blood plasma for efficient transport in the blood.

haemoglobin’s relationship with oxygen

• haemoglobin has an affinity for oxygen

• haemoglobin associates with oxygen in the lungs

• haemoglobin dissociates with oxygen in the tissues

what does haemoglobin’s ability to associate with oxygen depend on?

concentration of oxygen in the surrounding tissues

how do you measure concentration of oxygen in the surrounding tissues?

partial pressure - pressure contributed by 1 gas in a mixture of gases

oxygen transport in the lungs

haemoglobin loads/associates with oxygen in the lungs due to high partial pressure of oxygen in the lungs

oxygen transport in tissues

haemoglobin unloads/dissociates with oxygen at respiring tissues due to lower partial pressure of oxygen in respiring tissues

what is co-operative binding?

a property where the binding of one molecule to a protein influences the binding of subsequent molecules

what happens during the first oxygen molecule binding?

initially, haemoglobin has a lower affinity for oxygen so the first oxygen molecule binds with difficulty because the haem groups are less accessible

what happens during the second and third oxygen molecules binding?

after the first oxygen molecule binds, haemoglobin undergoes conformational shift which makes haem groups more accessible and increases haemoglobin’s affinity for oxygen. this means that the second and third oxygen molecules bind more easily.

what is a conformational shift?

when the tertiary and quaternary structure change

what happens when the fourth oxygen molecule binds?

it is harder to bind because the majority of binding sites are occupied so it is less likely that a single oxygen molecule will find the fourth binding site.

what does maximum saturation mean?

all haemoglobin proteins associated with 4 oxygen molecules