Question
The light micrograph shows tumour tissue from a patient’s lung.
(a) State one cause of lung cancer.
(b) Suggest one difference between tissue taken from a lung cancer tumour and normal lung tissue that might be seen in micrographs.
(c) The lung tumour in the light micrograph was slow-growing. Predict with a reason what would have been visible in the micrograph if the tumour was growing rapidly.
Answer/Explanation
Answer:
(a)
a. smoking/tobacco;
b. passive smoking;
c. Radon/other radiation;
d. exposure to arsenic/asbestos/smoke from coal burning/fires/silica/rock
dust/vehicle exhaust fumes/nitrogen oxides;
(b)
a. fewer/smaller/lack of alveoli/air spaces;
b. many cells/nuclei per area / much denser tissue;
c. more cells undergoing mitosis (in the tumour);
(c)
See
a. more mitosis
OR
cells in prophase/metaphase/anaphase/telophase;
Why
b. more dividing cells/tumour cell divide uncontrollably
OR
a higher mitotic index;
Question
Trends in tobacco smoking and mortality due to lung cancer were measured in male and female smokers aged 35 to 59 living in the United Kingdom from 1950 to 2000. The first graph represents the proportion of smokers in the population. The second graph represents the mortality rate (deaths per year per 100 000 people) from lung cancer.
The incidence of lung cancer in 75-year-old males was studied comparing current smokers, former smokers and non-smokers.
a. Calculate the change in the percentage of the male population that smoked from 1950 to 2000.
b. Compare and contrast the trends in smoking behaviour between males and females between 1950 and 2000.
[2]
c. Evaluate the evidence provided by the data in the graphs for smoking as a cause of lung cancer.
d. Describe the relationship between the incidence of lung cancer and stopping smoking.
e. Explain evidence from the data in the table that could be used to persuade a smoker to give up smoking.
f. Among 75 -year-old lifelong non-smokers the percentage incidence of lung cancer was \(0.01 \%\). Suggest one possible cause of lung cancer in non-smokers.
g. State two respiratory diseases, other than lung cancer, caused by smoking.
▶️Answer/Explanation
Ans:
a. «-» \(44 \ll \% » \checkmark\)
Allow answers in the range of 43 «\%» to 45 «\%»
b. Similarity:
a. both show an overall decrease
OR
both decrease after \(1970 \checkmark\)
Difference:
b. proportion of male smokers is always higher than female
OR
men decrease more
OR
women first increase «till 1970» and then decrease whereas men decrease throughout OR
males highest value in 1950 and females in \(1970 \checkmark\)
There should be one similarity and one difference
c. a. more smoking leads to more deaths
OR
there is a correlation between smoking and deaths from lung cancer \(\checkmark\)
b. «nevertheless» male mortality peaks in 1960 when declining numbers of smoking \(\checkmark\)
c. cancer takes time to develop causing delay between changes in smoking and cancer \(\checkmark\)
d. correlation does not prove causation \(\checkmark\)
e. the data shows deaths from lung cancer, not incidence \(\checkmark\)
d. a. highest incidence with continual smoking \(\checkmark\)
b. negative correlation/incidence decreases with length of time not smoking \(\checkmark\)
c. decrease «in incidence» occurs at less than 10 years since stopping smoking \(\checkmark\)
d. after 30 years incidence is not much more than non-smokers \(\sqrt{ }\)
e. a. incidence of lung cancer decreases the earlier the smoker gives up smoking \(\checkmark\)
b. continuing smoking increases incidence of lung cancer \(\sqrt{ }\)
c. after 30 years of not smoking the risk of lung cancer is low/similar to non-smokers \(\checkmark\)
Accept vice versa
f. passive smoking/second hand smoke/exposure to radon/asbestos/pollution/smog/genetic predisposition \(\checkmark\)
g.
a. emphysema ✔
b. bronchitis ✔
c. COPD ✔
d. asthma ✔
e. pneumonia ✔
Only mark first two
Question
The diagram shows the structure of an alveolus and an adjacent capillary.
a. Outline the functions of type I and type II pneumocytes.
b. Explain how gases are exchanged between the air in the alveolus and the blood in the capillaries.[3]
▶️Answer/Explanation
Ans:
a. type I:
a. carry out gas exchange
OR
diffusion of gases/ \(\mathrm{CO}_2 / \mathrm{O}_2 \sqrt{ }\)
type II:
b. secrete fluid/surfactant \(\checkmark\)
b. a. \(\mathrm{O}_2\) concentration in alveolar air greater than in capillary/blood «prior to gas exchange»
OR
hemoglobin in blood binds oxygen maintaining the concentration gradient \(\checkmark\)
b. \(\mathrm{O}_2\) gas dissolves in water lining the alveolus \(\checkmark\)
c. \(\mathrm{O}_2\) diffuses through wall of alveolus and capillary into blood \(\checkmark\)
d. \(\mathrm{CO}_2\) concentration in blood greater than in alveolar air «prior to gas exchange» \(\checkmark\)
e. \(\mathrm{CO}_2\) diffuses through wall of capillary and alveolus into alveolar airspace \(\checkmark\)