| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ1.21 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 21 | Adapted from | N/A |
Question
The graph below shows the oxygen dissociation curve at a low CO2 concentration.
Outline the main changes in the lungs that occur in patients with emphysema.
State a treatment for emphysema.
An increase in metabolic activity results in greater release of CO2 into the blood. On the graph, draw the oxygen dissociation curve during intense exercise when the CO2 concentration of the blood is high.
Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.
Markscheme
a. air sacs/alveoli break down/rupture
b. creating one larger air space instead of many small ones / reduces the surface area of the lungs
c. loss of elasticity of lung tissue
supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant
curve has to be towards the right and starting together
Must start together but can finish slightly below the original curve.
a. increased levels of CO2 lower the pH of the blood
b. «which results in» decreased affinity of the hemoglobin for oxygen / greater release of oxygen
c. this shifts the oxygen dissociation curve to the right/Bohr shift
