haemoglobin

Question 1

structure

Answer 1

quaternary structure
4 amino acid chains associated together
globular proteins
haem group containing iron ions

Question 2

how changes in the shape of haemoglobin result in the S shaped oxyhaemoglobin dissociation curve

Answer 2

first oxygen binds to Hb causing change in shape
allowing more O2 to bind easily
cooperative binding

Question 3

why does the binding of one molecule of oxygen to haemoglobin make it easier for a second oxygen molecule to bind

Answer 3

binding of first oxygen changes tertiary or quaternary structure of haemoglobin
leading to another binding site

Question 4

describe how haemoglobin normally loads oxygen in the lungs and unloads in a tissue cell

Answer 4

oxygen combines to produce oxyhaemoglobin
each haemoglobin molecule carry 4 molecules of oxygen
high partial pressure of oxygen in the lungs
haemoglobin almost 100% saturated
unloads at low oxygen tension in tissues
presence of carbon dioxide displaces curve further to right- increases oxygen dissociation
allows more O2 to be unloaded
increase temp allows more O2 to be unloaded
low pO2 occur in respiring tissue

Question 5

describe how haemoglobin is involved in absorbing oxygen in the lungs and transporting it to respiring tissues

Answer 5

diffusion of oxygen into rbc
high affinity of haemoglobin in high O2 concentration
therefore loads
oxyhaemoglobin formed
unloads at low affinity of oxygen
???

Question 6

during exercise, the rate of respiration of muscle cells increases. explain what causes human haemoglobin to unload more oxygen to these cells

Answer 6

partial pressure on oxygen in muscle falls more
more CO2 produced
lowers pH
increase in temperature
percentage saturation of Hb falls- lowers affinity
dissociation curve to right- Bohr shift

Question 7

advantage to a shrew having Hb with a dissociation curve shifted to the right. explain this advantage

Answer 7

at tissues at low pp oxygen- the shrews Hb is less saturated with oxygen/has reduced affinity
haemoglobin releases oxygen more readily
allowing greater demand for greater respiration rate

Question 8

suggest advantage to a lugworm of having haemoglobin that has an oxygen dissociation curve to the left of the curve for human Hb

Answer 8

lugworm= lower pp of oxygen in lungs
has Hb with higher oxygen affinity
Hb can load more oxygen at lower pp of oxygen

Question 9

explain how foetal Hb makes it possible for the foetus to take oxygen from the mothers blood

Answer 9

foetal Hb has greater affinity and binds more readily to oxygen
at same ppO2, foetal has higher saturation
maintains diffusion gradient across placenta