Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
Answers to end-of-chapter questions
9 a
ii U / Golgi apparatus, packages proteins into
vesicles;
for secretion; [2]
c Award 2 marks for the correct answer. If
answer is incorrect, award 1 mark for the
correct working.
length of cell P on page = 73 mm = 73 000 µm
magnification = ×750
actual length = 73 000 ÷ 750 = 97 µm [2]
d cell P – cilia beat / move back and forth;
move mucus;
upwards / towards throat;
cell R – secretes mucus;
mucus traps, dust / bacteria / viruses / pollen;
prevents entry to, alveoli / gas exchange
surface; [max. 4]
[Total: 16]
Structure Trachea Respiratory
bronchiole
smooth muscle cells ✔ ✘
ciliated epithelial cells ✔ ✔
mucous glands ✔ ✘
cartilage ✔ ✘
elastic fibres ✔ ✔
Award 1 mark for each row [5]
b mucus secreted;
by mucous glands (in the trachea) / goblet
cells (in trachea and bronchi);
bacteria / viruses / pathogens, stick to mucus;
cilia move mucus, upwards / towards throat;
mucus and pathogens swallowed;
destroyed by acid in stomach;
macrophages / phagocytes, in the alveoli;
engulf and digest any pathogens; [max. 5]
[Total: 10]
10a oxygen diffuses down its concentration
gradient;
from alveolar air into red blood cells;
carbon dioxide diffuses down its
concentration gradient;
from, red blood cells / plasma, to alveolar air;
across epithelial cells of alveolus and
endothelium of capillary; [max. 4]
b breathing / ventilation;
introduces, fresh air / atmospheric air;
removes, stale air / air rich in carbon dioxide;
[3]
c increase
depth of breathing;
rate of breathing;
expansion of alveoli to give a larger surface
area;
diameter of airways; [max. 3]
[Total: 10]
11a tar stimulates, goblet cells / mucous glands,
to secrete more mucus;
paralyses / destroys, cilia;
mucus not moved up the, bronchioles /
bronchi / trachea / airways;
mucus accumulates in the airways;
bacteria multiply within the airways;
(leads to) chronic bronchitis;
tar contains, carcinogens / named
carcinogen; e.g. benzpyrene
(tar) settles on bronchial, epithelial cells /
epithelium;
mutation(s) / change to DNA;
growth of tumour;
bronchial carcinoma / lung cancer; [max. 8]
b nicotine:
increases heart rate;
increases blood pressure;
increases chance of blood clotting /
promotes thrombosis;
decreased flow of blood to, extremities /
fingers / toes; [max. 3]
carbon monoxide:
combines (irreversibly) with haemoglobin;
forms carboxyhaemoglobin;
reduces oxygen carrying capacity of,
haemoglobin / blood;
damages lining of arteries;
promotes atherosclerosis; [max. 3]
[Total: 14]
12a fewer alveoli;
larger air spaces;
fewer capillaries;
scar tissue in, bronchioles / bronchi;
few / no, cilia;
few / no, goblet cells;
enlarged mucous glands;
Cambridge International AS and A Level Biology © Cambridge University Press 2014