Transport of oxygen and carbon dioxide in the blood

Question 1

How are erythrocytes adapted to their role?

Answer 1

biconcave shape which increases the surface area available for gases to diffuse and helps them to pass through narrow capillaries. They also have no nuclei and few organelles to maximise space available for haemoglobin.

Question 2

What happens when oxygen binds to haemoglobin?

Answer 2

haemoglobin changes shape so that it’s easier for the next oxygen molecules to bind (positive cooperativity)

Question 3

What does an oxygen dissociation curve show?

Answer 3

the affinity of haemoglobin for oxygen, the binding of one molecule increases the saturation massively due the positive cooperativity so small changes in pO2 massively increase saturation of haemoglobin

Question 4

What is the effect of carbon dioxide on haemoglobin?

Answer 4

lots of carbon dioxide means haemoglobin gives up oxygen more easily (bohr effect)

Question 5

Why is the bohr effect important?

Answer 5

The haemoglobin in active tissues that have lots of carbon dioxide will give up its oxygen more easily and in lungs where there is little carbon dioxide, the oxygen binds to the Hb more easily

Question 6

Why does fetal haemoglobin have a higher affinity for oxygen?

Answer 6

foetus is completely dependant on mother for oxygen. It has to have a higher affinity so that oxygen is transferred from mother’s blood to foetus in placenta

Question 7

How is carbon dioxide transported?

Answer 7

dissolved in plasma, combined with amine groups of haemoglobin to form carbaminohaemoglobin and converted into hydrogen carbonate ions in red blood cells

Question 8

What happens to carbon dioxide in red blood cells?

Answer 8

reacts with water to form carbonic acid with carbonic anhydrase as the enzyme which dissociates to form hydrogen ions and hydrogen carbonate ions.

Question 9

What is the chloride shift?

Answer 9

negatively charged hydrogen carbonate ions move out RBC and negatively charged chloride ions diffuse in to maintain electrical balance

Question 10

How does carbon dioxide leave the RBCs at the lungs?

Answer 10

carbonic acid is broken down into carbon dioxide and water. hydrogen carbonate diffuses back into RBC and reacts with hydrogen ions to form more carbonic acid. Chloride ions diffuse back out again