exchange and transport

Question 1

Using your knowledge of the structure of bronchioles, suggest how their diameter might become reduced.

Answer 1

contraction of smooth muscle ;
circular (muscle) ;
extra mucus production ;
inflammation ;

Question 2

Explain why it is difficult to expel air from the lungs if the bronchioles become reduced in diameter.

Answer 2

(reduced diameter means) increased ,
 resistance to air flow / friction ;
idea that exhalation is passive / no
(muscular) force behind exhalation / requires
additional, force / pressure, to exhale;

Question 3

Name the two types of epithelial tissue found in the lungs and airways.

Answer 3

columnar / ciliated ;

squamous / pavement ;

Question 4

The epithelial cells in the lungs are arranged into structures called alveoli.Explain how the alveoli create a surface for efficient gaseous exchange.

Answer 4

1.wall is one cell thick for short(er)
 diffusion, distance / pathway ;
2.squamous, cells / epithelium , provide
 short diffusion distance / pathway ;
3.elastic so, recoil / expel air / helps
 ventilation ;
4.create / maintain, concentration
 gradient / described ;
5.large number (of alveoli) provide large(r)
 surface area ;
6.small size (of alveoli) provide large(r)
 surface area to volume ratio ;
7.(cells secrete) surfactant to maintain
 surface area ;

Question 5

To improve gaseous exchange, the air in the alveoli is refreshed by ventilation. The air movement created by ventilation can be recorded using suitable apparatus. Name the apparatus used to record these air movements.

Answer 5

spirometer

Question 6

When the rubber sheet is pulled down the balloons expand.

Explain why the balloons expand.

Answer 6

1 volume, inside / of, jar increases ;
2 pressure inside, jar / balloons, decreases ;
3 to below pressure in atmosphere ;
4 (therefore) air, moves / pushed / forced, into, balloons /
glass tube ;

Question 7

Explain the meaning of the term tidal volume

Answer 7

volume of air, inhaled / exhaled ;
in, one / each, breath ;
during, steady / regular, breathing ;

Question 8

Suggest how the teacher may have used the model to demonstrate tidal volume.

Answer 8

up / down, movements (of rubber sheet / band) ;
idea of: small / steady / regular, movements (of rubber
sheet) ;

Question 9

Explain the meaning of the term vital capacity.

Answer 9

the maximum volume of air ;

inhaled / exhaled, in one breath ;

Question 10

Suggest how the teacher may have used the model to demonstrate vital capacity.

Answer 10

idea that pulled down on rubber, sheet / band, as far as

possible and pushed up as far as possible ;

Question 11

List three reasons why a large, multicellular animal, such as a mammal, needs a transport system.

Answer 11

low / small, surface area to volume ratio ;
diffusion, too slow / distance too great ;
to supply enough, oxygen / (named) nutrients ;
to prevent, CO2 / (named) waste product, building up ;
active ;

Question 12

Explain why cartilage is essential in the trachea.

Answer 12

(provides) strength / support, to keep, it / trachea / airway,
open
OR
(provides) strength / support, to prevent collapse ;
during, inspiration / inhaling / breathing in ;
volume of, chest cavity / thorax / lungs, increases ;
low(er) / negative, pressure in, trachea / thorax / lungs ;

Question 13

All living organisms exchange substances with their external environment. The following data apply to an average person:
• the surface area of the body is approximately 1.8 m2 • the volume of the body is approximately 0.07 m3 • the surface area of the lungs is approximately 70 m2.Comment on the significance of this information for gas exchange.

Answer 13

body has small surface area to volume ratio
OR
lungs, provide / have, large surface area to volume ratio ;
correct calculation of (one) surface area to volume ratio ;
idea of:
body SA / SA:Vol is not big enough to meet body’s needs
OR
lung SA / SA:Vol is big enough to meet body’s needs ;
oxygen into (blood / body) and carbon dioxide out (of blood /
body) ;

Question 14

Explain what causes the change in the volume of air during exhalation

Answer 14

1 (external) intercostal muscles / diaphragm, relax ;
2 rib cage / ribs, move down OR diaphragm, moves /
pushed, up ;
3 volume of, thorax / chest cavity / lungs, drops /
decreases ;
4 pressure inside, thorax / chest cavity / lungs, increases ;
5 above, external / atmospheric, pressure ;
6 air leaves down pressure gradient ;
7 (elastic) recoil of alveoli ;
QWC
intercostal, diaphragm, recoil, volume
thorax, pressure, gradient

Question 15

About 1 dm3 of air cannot be expelled from the lungs. This is known as the residual volume.
Suggest why it is not possible to expel all the air from the lungs.

Answer 15

idea that:
thorax / rib cage / lungs, cannot be completely ,
compressed / flattened ;
trachea / bronchi, held open by cartilage ;
bronchioles / alveoli, held open by elastic fibres ;

Question 16

The mammalian lungs contain many air sacs.

Name the air sacs and state why there are many air sacs in the lungs.

Answer 16

alveoli ;

to provide large(r), surface area / SA ;

Question 17

Name the type of epithelium in the walls of the air sacs.

Answer 17

squamous / pavement ;

Question 18

The air sacs contain many elastic fibres.

Explain the role of these elastic fibres during ventilation.

Answer 18

to prevent bursting ;
recoil ;
to return air sac to original, size / shape ;
to help expel air ;

Question 19

Explain how refreshing the air in the air sacs helps to maintain a steep diffusion gradient.

Answer 19

increases, partial pressure / concentration, of oxygen
(in the air sac) ;
so concentration of oxygen (in the air sac) is higher than
that in the blood ;
decreases, partial pressure / concentration, of
carbon dioxide (in air sac) ;
so concentration of CO2 (in the air sac) is lower than
that in the blood ;

Question 20

Describe and explain one other way in which a steep diffusion gradient is maintained in the lungs.

Answer 20

EITHER
D1 (continuous) blood flow (in the capillaries) ;
E1 to, bring in (more) carbon dioxide / take away (more)
oxygen ;
OR
D2 oxygen combines with haemoglobin ;
E2 to keep concentration in, blood / plasma, low ;

Question 21

Describe how the spirometer would be used to measure tidal volume.

Answer 21

1 idea of not breathing through nose ;
2 subject breathes , evenly / normally / regularly ;
3 idea of (measure) height / amplitude , of waves
(from trace) ;
4 measure at least three waves and calculate mean ;
5 detail of how spirometer works ;

Question 22

Describe how you could use a spirometer trace to measure the rate of oxygen uptake.

Answer 22

1 measure , volume of oxygen used /
decrease in volume in chamber ;
2 one detail of how to measure volume change ;
3 measure time taken (to use this oxygen) ;
4 divide (volume) by time taken ;

Question 23

Suggest two factors that should be considered when carrying out a risk assessment for an experiment using a spirometer.

Answer 23

1 check health of volunteer ;
2 oxygen used ;
3 new / sterilised / disinfected ,
 mouthpiece (for each volunteer);
4 idea of: soda lime working ;
5 sufficient oxygen in chamber ;
6 water level not too high / water must not enter tubes ;
7 ensure valves working correctly ;

Question 24

State two features of the alveoli that enable efficient gaseous exchange.

Answer 24

1 large, surface area / SA :VOL ;
2 (alveolar) wall / epithelium, one cell thick ;
3 (made of) squamous, cells / epithelium ;
4 ref to surfactant ;
idea of:
5 (very) close to, capillaries / blood supply
OR
rich blood supply / many capillaries ;

Question 25

Explain why a single-celled organism, such as Euglena, does not need a specialised area to carry out gaseous exchange.

Answer 25

large surface area to volume ratio ;
small so demand for, O2 / CO2, is low ;
idea of:
diffusion (alone) is adequate to meet needs ;

Question 26

Outline the mechanism of inspiration.

Answer 26

diaphragm / intercostal muscles, contract :
diaphragm moves down / ribs move upwards
and outwards ;
volume of thorax increased ;
pressure inside thorax falls ;
to below atmospheric pressure (so air enters
lungs) ;
QWC
diaphragm, intercostal, volume, pressure,
thorax, thoracic cavity

Question 27

Chamber T contains a chemical that absorbs carbon dioxide.
Suggest a chemical that could be used in chamber T to absorb carbon dioxide.

Answer 27

soda lime / sodium hydroxide / potassium

hydroxide / calcium hydroxide ;

Question 28

Explain why a person using the spirometer to measure their vital capacity should wear a nose clip.

Answer 28

to ensure all air breathed comes from chamber
OR
to prevent, escape of air / entry of air, through
nose ;
makes results invalid

Question 29

State two other precautions that should be taken when using a spirometer to measure vital capacity.

Answer 29

use (medical grade) oxygen / fresh air ;
ref. to health of subject ; e.g. asthmatics
ref to correct functioning of equipment ;
disinfect

Question 30

Explain, using the term surface area to volume ratio, why large, active organisms need a specialised surface for gaseous exchange.

Answer 30

large / active, organisms have high(er), demand for oxygen / need
to remove CO2 ;
small(er), surface area to volume ratio / SA:V / surface area:volume
;
surface area too small / distance too large / diffusion takes too long
(to supply needs) ;

Question 31

Outline how the diaphragm and intercostal muscles cause inspiration

Answer 31

diaphragm (contracts / flattens and) moves downwards ;
intercostal muscles contract to move ribs, up / out ;
increase volume of thorax ;
reduce pressure inside thorax ;
to below atmospheric pressure/creates pressure gradient / AW ;