The Transport of Oxygen Flashcards
what is haemoglobin?
-conjugated protein
-4 polypeptide chains 2 alpha 2 beta called globin proteins
-each globin molecules has a non protein prosthetic group called haem, each haem consists of iron
-each haem group can combine with one molecule of oxygen to form oxyhaemoglobin
the combining of oxygen and haemoglobin is a reversible reaction what does this mean?
-when oxygen levels are low the oxyhaemoglobin dissociates and oxygen is released
-in conditions where oxygen levels are high oxyhaemoglobin is formed
when the first oxygen molecule there is a conformational change what does this mean?
-this distortion in the haemoglobin results in an easier uptake of the remaining three oxygen molecules also known as cooperative loading
the cooperative loading/ enhancement of the subsequent binding of the 4 oxygen molecules results in what type of graph and what does it show?
-produces a sigmoid curve which shows how oxygen rapidly binds/ saturated haemoglobin at low partial pressures of oxygen
when is oxyhaemoglobin formed and when is oxygen dissociated from it?
-oxyhaemoglobin is formed when oxygen levels are high and oxygen dissociates from haemoglobin when oxygen levels are low
where does oxyhaemoglobin form in mammals and where does oxygen dissociate?
-oxyhaemoglobin forms in the lungs as oxygen levels are high due to rapid gaseous exchange
-dissociation takes place in the tissues where oxygen levels are low due to respiration
what does partial pressure mean?
-its a measure of gas in a mixture of gases
-the partial pressure of oxygen means the concentration of oxygen so the more oxygen there is the higher the partial pressure
the fourth and last haem group to bind with oxygen binds over 700 times faster than the first group, why is this?
-after the first haem group combines haeoglobin undergoes a conformational change allowing each group to bind faster known as cooperative loading
when is blood 100% saturated?
-when every haem group is carrying four molecules of oxygen
what is oxygen uptake like in the lungs where the partial pressure is 14kPa ?
-the blood comes into contact with air, for a short period of time the haemoglobin approaches full saturation which is over 95%
what is oxygen uptake like in respiring tissues such as liver or brain where the partial pressure is around 5kPa?
-as most oxygen is used during respiration the levels if oxygen are relatively low
-at this partial pressure haemoglobin is about 50% saturated as it unloads half of its oxygen to the respiring tissues to be used
what is oxygen uptake like in tissues that are respiring rapidly like contracting muscle cells where the partial pressure is around 2kPa?
-as the partial pressure is extremely low the haemoglobin saturation drops to about 10% so 90% of the oxygen unloaded is used to provide sufficient levels of oxygen this is known as rapid dissociation
what does the loading tension of oxygen mean?
-partial pressure at which haemoglobin is 95% saturated with oxygen
what does the unloading tension of oxygen mean?
-partial pressure at which haemoglobin is 50% saturated with oxygen
how can carbon dioxide effect the the unloading of oxygen?
-carbon dioxide reduces the affinity of haemoglobin for oxygen at the partial pressure of oxygen found in the body
-unloading of oxygen in the capillaries of tissues is helped by high concentrations of carbon dioxide produced by cellular respiration
what is the bohr effect on a sigmoid graph?
-the oxygen dissociation curve moves to the right causing increased dissociation of oxygen from haemoglobin which results in more oxygen being available for cells
as the CO2 concentration increases…
-more oxygen is released from haemoglobin
why is it important that high levels of carbon dioxide results in high dissociation of oxygen from haemoglobin?
-it is important as it ensures that actively respiring tissues which has increased demands for oxygen, will receive oxygen more effectively
how else can the bohr effect occur besides and increased level of oxygen?
-a drop in pH which results in increased acidity due to increased carbon dioxide transport
-increase in temperature due to respiration
when does the bohr effect occur in the body?
-during periods of strenuous exercise
-this means that increased oxygen becomes available to tissues in times of greatest need
what is myoglobin and where is it found?
-an oxygen transporting pigment found in red muscle e.g. skeletal and heart muscle
what is the structure of myoglobin?
-one polypeptide chain with a single haem group
what is the oxygen dissociation curve look like for myoglobin?
-the curve is displaced to the left for myoglobin because it combines more readily with oxygen than haemoglobin
if the curve moves to the left for myoglobin what does this mean?
-myoglobin has a higher affinity for oxygen than haemoglobin causing myoglobin to remain saturated at lower partial pressures of oxygen than haemoglobin
when is the only time than oxygen dissociates with myoglobin? is oxygen stays with myoglobin what does this serve as?
-when partial pressures of oxygen are lower than 1kPa
-this means that it serves as an oxygen store and it has no role in oxygen transport and only releases oxygen when blood oxygen levels are very low such as during strenuous exercise
why is myoglobin important to serve as an oxygen store in red muscle?
-it ensure that muscle metabolism can remain aerobic at lower partial pressures of oxygen and so delays the onset of anaerobic respiration which doesnt supply ATP energy and supply lactic acid which is a toxic waste product
what type of animal has a particularly large amount of myoglobin? and why?
-diving animals e.g. whales
-this is because they have to stay underwater for large periods of time where oxygen levels are low
what is the effect of altitude on oxygen transport by haemoglobin?
-as height increases above sea levels the overall atmospheric pressure and partial pressure of oxygen is reduced
-at higher altitudes human haemoglobin cannot become fully saturaturated
the human haemoglobin cannot become fully saturated at high altitudes however after a few days acclimatization occurs what does this mean?
-the number of red blood cells increase which allows for more efficient transport of the oxygen that is available in the atmosphere
-maximises the diffusion of oxygen into the blood
how do populations that have lived in high altitudes e.g. llamas survive?
-their haemoglobin has evolved and now can saturate at low pO2 levels than the more typical lower altitude populations
