haemoglobin and oxygen transport

what are two adaptations of a red blood cell and how do they allow large amounts of oxygen in a short time?

• (biconcave shape causes RBCs to) have a large S.A to volume ratio for diffusion

• they are flat/thin so oxygen can reach all of the haemoglobin / centre rapidly

what are haemoglobins?

a group of globular proteins with a quaternary structure

what do haemoglobins consist of?

• four polypeptide chains linked to form a spherical molecule

• each polypeptide chain is associated with a haem group containing a Fe²⁺ ion

• Fe²⁺ can be combined with one O₂ molecule

what is the role of harmoglobin?

oxygen transport

where does oxygen bind to haemoglobin in the body and what is formed when they bind?

• in the lungs

• forms oxyhaemoglobin

what is the process called when oxygen binds to haemoglobin?

association/loading

what is the process called when oxygen leaves haemoglobin?

dissociation/unloading

what does the term affinity of haemoglobin for oxygen mean?

the ability of haemoglobin to attract, or bind to oxygen

what factors affect haemoglobin's affinity for oxygen?

• the partial pressure of oxygen (pO₂)

• haemoglobin saturation

• the partial pressure of carbon dioxide (pCO₂)

what is partial pressure?

a measure of concentration of a specific gas within a mixture of gases

where does haemoglobin have a high affinity and a low affinity for oxygen?

• high - oxygen rich areas, e.g. lungs

• low - oxygen deprived areas, e.g. respiring tissues

what is cooperative binding?

the binding of each oxygen changes the shape of the haemoglobin, making it easier for the next to bind

how does pO₂ affect haemoglobin saturation?

higher pO₂ increases haemoglobin saturation

what is the Bohr effect?

reduced pH decreases haemoglobin's affinity for oxygen

how does increasing partial pressure of carbon dioxide (pCO₂) affect haemoglobin's affinity for oxygen?

decreases affinity, promoting oxygen dissociation

what effect does high partial pressure of carbon dioxide (pCO2) have on the oxygen dissociation curve?

it shifts to the right

in which direction does the oxygen dissociation curve shift during high respiration and what is the advantage of this?

it shifts right

• haemoglobin has a lower affinity for oxygen

• so more oxygen is available for respiration

how does aerobic respiration lead to a change in plasma pH? (3)

• during aerobic respiration carbon dioxide is produced

• CO₂ dissolves in the blood plasma to form carbonic acid

• this causes an increase in H⁺ ion concentration

what is the advantage to tissue cells of a reduction in haemoglobin’s affinity for oxygen when plasma pH deceases?

• low pH is due to the high rate of respiration

• cells need more oxygen

• so more oxygen is released

how is oxygen in a RBC made available for respiration in active tissues?

• low pH is due to increased CO₂ during respiration

• this increases dissociation of haemoglobin

• oxygen diffuses from RBC to tissues

what is the haemoglobin affinity of a foetus in the womb like?

• higher affinity

• dissociation curve is shifted to the left

explain the advantage of the curve of foetal haemoglobin being different to an adult (3)

• foetal haemoglobin have a higher affinity for oxygen

• so becomes saturated at a lower partial pressure

• at partial pressures when adult haemoglobin dissociates, foetal haemoglobin takes up oxygen

what is the haemoglobin affinity of animals living in low oxygen environments like?

• higher affinity

• dissociation curve is shifted to the left

explain the advantage of the curve of animals living in low oxygen environments being different to animals living in high altitudes (3)

• high altitudes have a low partial pressure of oxygen

• so have a high affinity of haemoglobin with oxygen

• so sufficiency oxygen is supplied to cells/tissue

what is the haemoglobin affinity of small organisms with high SA:V/high metabolic rate like?

• lower affinity

• dissociation curve is shifted to the right

why do high metabolic rate animals have haemoglobin with low oxygen affinity?

allows easier oxygen unloading for high demand