Dissociation curves

Question 1

What is shown on a oxygen dissociation curve?

Answer 1

percentage saturation of haemoglobin in the blood is plotted against the partial pressure of oxygen (pO2)

shows the affinity of haemoglobin for oxygen

Question 2

What affect does change in partial pressure of oxygen have on the saturation?

Answer 2

a small change can cause a significant difference to the saturation of haemoglobin with oxygen

because once the first molecule becomes attached, the change in shape means other molecules are added rapidly

Question 3

Why does the curve level out?

Answer 3

levels out at the highest partial pressures of oxygen because all the haem group are bound to oxtygen

so the haemoglobin is saturated and cannot take up any more

Question 4

What affect does a change in partial pressure of oxygen have on transprt?

Answer 4

high partial pressure in the lungs result in haemoglobin becomes loaded with oxygen

small drop in oxygen levels in respiring tissures means oxygen is released rapidly from the haemoglobin into the cells.

This effect is enhanced by the relatively low pH in the tissues compared to the lungs

Question 5

What is the Bohr effect?

Answer 5

as partial pressures of CO2 rise, haemoglobin gives up oxygen more easily

Question 6

Why is the Bohr effect important in the body?

Answer 6

in active tissues with a high partial pressure for carbon dioxide, haemoglobin gives up its oxygen more readily

in the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoblobin molecules easily

Question 7

What is the difference between adult and fetal haemoglobin?

Answer 7

has a higher affinity for oxygen dissociation curve is left-shifted can remove oxygen from the mothers blood

Question 8

Why is it important that fetal haemoglobin has a higher affinity for oxygen?

Answer 8

• fetuses are dependant on its mother for its supply for oxygen
• oxygenated blood from the mother runs close to the deoxygenated fetal blood in the placenta
• if the blood of the fetus and the mother had the same affinity for oxygen then no oxygen would be transferred
• placenta has a lower pp
  
  • ​​​maternal haemoglobin released oxygen at these low pp becomes less saturated
  • if the foetus had same affinity for oxygen, then it would not become saturated

Question 9

Why does the adult form of haemoglobin replace the fetal haemoglobin after birth?

Answer 9

because of its stronger affinity, it makes it for oxygen to be released so the fetus can receive oxygen from the mother when she is pregnant

Question 10

Why is llama haemoglobin dissociation curve left shifted to a camel?

Answer 10

• llama haemoglobin has higher affinity for O2 at lower pp
• O2 in lunngs of llama at lower pp than camel
• more likely llama haemoglobin will be saturated at any given pp