The Transport of Oxygen

Question 1

what is haemoglobin?

Answer 1

-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

Question 2

the combining of oxygen and haemoglobin is a reversible reaction what does this mean?

Answer 2

-when oxygen levels are low the oxyhaemoglobin dissociates and oxygen is released
-in conditions where oxygen levels are high oxyhaemoglobin is formed

Question 3

when the first oxygen molecule there is a conformational change what does this mean?

Answer 3

-this distortion in the haemoglobin results in an easier uptake of the remaining three oxygen molecules also known as cooperative loading

Question 4

the cooperative loading/ enhancement of the subsequent binding of the 4 oxygen molecules results in what type of graph and what does it show?

Answer 4

-produces a sigmoid curve which shows how oxygen rapidly binds/ saturated haemoglobin at low partial pressures of oxygen

Question 5

when is oxyhaemoglobin formed and when is oxygen dissociated from it?

Answer 5

-oxyhaemoglobin is formed when oxygen levels are high and oxygen dissociates from haemoglobin when oxygen levels are low

Question 6

where does oxyhaemoglobin form in mammals and where does oxygen dissociate?

Answer 6

-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

Question 7

what does partial pressure mean?

Answer 7

-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

Question 8

the fourth and last haem group to bind with oxygen binds over 700 times faster than the first group, why is this?

Answer 8

-after the first haem group combines haeoglobin undergoes a conformational change allowing each group to bind faster known as cooperative loading

Question 9

when is blood 100% saturated?

Answer 9

-when every haem group is carrying four molecules of oxygen

Question 10

what is oxygen uptake like in the lungs where the partial pressure is 14kPa ?

Answer 10

-the blood comes into contact with air, for a short period of time the haemoglobin approaches full saturation which is over 95%

Question 11

what is oxygen uptake like in respiring tissues such as liver or brain where the partial pressure is around 5kPa?

Answer 11

-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

Question 12

what is oxygen uptake like in tissues that are respiring rapidly like contracting muscle cells where the partial pressure is around 2kPa?

Answer 12

-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

Question 13

what does the loading tension of oxygen mean?

Answer 13

-partial pressure at which haemoglobin is 95% saturated with oxygen

Question 14

what does the unloading tension of oxygen mean?

Answer 14

-partial pressure at which haemoglobin is 50% saturated with oxygen

Question 15

how can carbon dioxide effect the the unloading of oxygen?

Answer 15

-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

Question 16

what is the bohr effect on a sigmoid graph?

Answer 16

-the oxygen dissociation curve moves to the right causing increased dissociation of oxygen from haemoglobin which results in more oxygen being available for cells

Question 17

as the CO2 concentration increases…

Answer 17

-more oxygen is released from haemoglobin

Question 18

why is it important that high levels of carbon dioxide results in high dissociation of oxygen from haemoglobin?

Answer 18

-it is important as it ensures that actively respiring tissues which has increased demands for oxygen, will receive oxygen more effectively

Question 19

how else can the bohr effect occur besides and increased level of oxygen?

Answer 19

-a drop in pH which results in increased acidity due to increased carbon dioxide transport
-increase in temperature due to respiration

Question 20

when does the bohr effect occur in the body?

Answer 20

-during periods of strenuous exercise
-this means that increased oxygen becomes available to tissues in times of greatest need

Question 21

what is myoglobin and where is it found?

Answer 21

-an oxygen transporting pigment found in red muscle e.g. skeletal and heart muscle

Question 22

what is the structure of myoglobin?

Answer 22

-one polypeptide chain with a single haem group

Question 23

what is the oxygen dissociation curve look like for myoglobin?

Answer 23

-the curve is displaced to the left for myoglobin because it combines more readily with oxygen than haemoglobin

Question 24

if the curve moves to the left for myoglobin what does this mean?

Answer 24

-myoglobin has a higher affinity for oxygen than haemoglobin causing myoglobin to remain saturated at lower partial pressures of oxygen than haemoglobin

Question 25

when is the only time than oxygen dissociates with myoglobin? is oxygen stays with myoglobin what does this serve as?

Answer 25

-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

Question 26

why is myoglobin important to serve as an oxygen store in red muscle?

Answer 26

-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

Question 27

what type of animal has a particularly large amount of myoglobin? and why?

Answer 27

-diving animals e.g. whales
-this is because they have to stay underwater for large periods of time where oxygen levels are low

Question 28

what is the effect of altitude on oxygen transport by haemoglobin?

Answer 28

-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

Question 29

the human haemoglobin cannot become fully saturated at high altitudes however after a few days acclimatization occurs what does this mean?

Answer 29

-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

Question 30

how do populations that have lived in high altitudes e.g. llamas survive?

Answer 30

-their haemoglobin has evolved and now can saturate at low pO2 levels than the more typical lower altitude populations