haemoglobin Flashcards
describe the function of hameoglobin
protein molecules with a quaternary structure that can load oxygen in one condition but offload it in a another
describe the structure of hameoglobin
primary
sequence of amino acids in the 4 polypeptide chains
secondary
each of the peptide chains coil to form an alpha helix held in place by hydrogen bonds
tertiary
each polypeptide chain coils further to form a 3D structure (giving it it’s specific shape) held in place by ionic bonds, disulfide bridges, hydrogen bonds
quaternary
all 4 polypeptide chains are joined to form a spherical molecule. Each polypeptide chain is associated with a prosthetic haem group
Explain the differences between haemoglobins in different organisms and the reasons for these differences
Affinity (chemical attraction) for oxygen: how readily haemoglobin binds to oxygen. This is controlled by the shape of the haemoglobin molecule.
Different haemoglobins have different affinities for oxygen - different organisms have haemoglobin with different amino acid sequences, therefore, different tertiary and quaternary structures which affects affinity for oxygen
explain what is meant by the loading of oxygen
when haemoglobin binds to oxygen in the lungs
explain what is meant by the offloading of oxygen
when hemoglobin releases it’s oxygen in respiring tissues
what does it mean if haemoglobin has a high affinity for oxygen
can take up oxygen more easily but releases it less easily
what does it mean if haemoglobin has a low affinity for oxygen
takes up oxygen less easily but releases it more easily
how many oxygen molecules can be carried by a single hameoglobin
4 molecules of oxygen can be carried by a single haemoglobin
how does haemoglobin change it’s affinity
it’s shape changes in the presence of substances like CO2
the new shape of the haemoglobin molecule binds more loosely to O2 as a result the haemoglobin releases it’s oxygen molecule
what is the role of hameoglobin in the blood
to transport oxygen
to be efficient at transporting oxygen haemoglobin must…..
1.
2.
- readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate from oxygen at those tissues requiring it
define prosthetic group
an inorganic group that is in the quaternary structure of a protein
how many beta and alpha chains are there in haemoglobin
2 beta chains
2 alpha chains
(= 4 polypeptide chains)
what holds the iron in place in each haem molecule
4 nitrogens
explain how haemoglobin is able to associate readily with oxygen at gas exchange surfaces but dissociate readily in respiring tissues
- high concentration of
oxygen in the lungs - low concentration of carbon dioxide in the lungs
- high affinity for oxygen in the lungs
- haemoglobin can bind to oxygen
- low concentration of oxygen in the tissues
- high concentration of carbon dioxide in the tissues
- low affinity for oxygen in the tissues
- haemoglobin can dissociate from oxygen
define conformational change
it binds causing something to change shape
explain the oxyhaemoglobin dissociation curve
ON PAPER FLASHCARD TOO
- it is hard for the first O2 to bind to the haem group as haem groups are the middle of the haemoglobin molecule
first oxygen causes a conformational change in the haemoglobin
- making it easier for the 2 + 3 O2 to bind to the haemoglobin
- the 4th O2 doesn’t bind as easily as it is hard to reach the 4th binding site
when you increase the concentration of CO2 what happens to the affinity of haemoglobin
it decreases
at the lungs because of the reduced concentration of CO2 what does it do to the oxygen dissociation curve
shifts to the left
at the respiring tissues because of the increase CO2 conc, what does it do to the oxygen dissociation curve
shifts to the right
describe and explain the Bohr Effect
- haemoglobin has a reduced affinity for oxygen in the presence of CO2
- it loads oxygen less readily and unloads more easily (BOHR EFFECT)
- dissolved CO2 is acidic so causes the haemoglobin to change shape
- at gas exchange surface there is little CO2, the affinity for oxygen is high so oxygen loads more readily
- at respiring tissues the carbon dioxide concentration is high, the affinity for oxygen is low, so oxygen is readily unloaded
describe and explain the shape of the oxyhaemoglobin dissociation curve
- at low partial pressures oxygen has a low affinity for oxygen so oxygen dissociates where the curve is shallow
-the curve becomes steeper as affinity for oxygen increases
-curve levels off at nearly 100% saturation at high partial pressures of oxygen so haemoglobin has a high affinity for oxygen so associates less easily
explain with reference to haemoglobin how animals are well adapted to their environment
an animal that lives in an evironment with a low partial pressure of oxygen
will have haemoglobin with high affinity for oxygen
the curve is shifted to the left which allows saturated haemoglobin at low partial pressures
