AQA Biology Unit 1 Lungs and breathing revision with past questions and answers

1. Lungs
Structure
The lungs are the site of gas exchange
in mammals.
They are not locate outside the body
because
1) the air is not dense enough to
support them
2) they would dry out
3) the lungs are very delicate
the lungs are supported by the ribcage
which can be moved by the use of the
intercostal muscle.
Trachea
This is a flexible airways supported by
rings of cartilage which prevent the trachea from collapsing when the air
pressure inside falls.
The walls are made up of muscle, lined with ciliated epithelium and goblet cells
1) the goblet cells produce mucus which traps dirt and bacteria.
2) The cilium moves the mucus up into the throat where it is swallowed.
Bronchi:
Bronchi have 2 divisions of the trachea. The larger bronchi are supported by
cartilage.
Bronchioles:
These are branching subdivisions of the bronchi. The walls are made of the
muscle lined with epithelial cells. The muscle enables them to control the air in
and out.
Alveoli:
Very small air-sacs at the end of the bronchioles. It contains collagen and elastic
fibres. Alveoli is the site of gas exchange where the CO2 goes into he alveoli and
the O2 goes into the blood stream.
Danger:
The lungs increase and decrease in size continuously. When an organ increases
in size in the body, it could touch other organs because there isn’t enough space.
This can become a risk because when living tissue rubs against another, it could
cause friction, which could cause tissue damage and kill the cells.

2. Mechanism of Breathing:
The two breathing processes are INHALATION and EXHALATION.
The breathing system does not have a foxed shape as it has the ability to move,
whilst staying in a protective ribcage. This means that the rob cage too can
moves positions.
INHALATION
1) When we inhale, our
lungs fill with air.
2) AS they fill with air,
they become
ENLARGED.
3) Thus, the ribcage
moves UPWARDS and
OUTWARDS to make
more room in the
thorax.
4) The overall effect is
that our chest
EXPANDS.
The pressure changes in
the lungs due to…
1) The DIAPHRAGM - a sheet of muscle that separates the thorax and the
abdomen.
2) The INTERNAL INTERCOSTAL MUSCLES – leads to EXPIRATION
3) The EXTERNAL INTERCOSTAL MUSCLES - leads to INSPIRATION
DIAPHRAGM
The diaphragm Is a dome shape when we exhale. However, when we inhale it
CONTRACTS and FLATTENS. This results in a change in volume in the thorax as
the volume increases when the diaphragm is flattened.
As the volume increases, the internal air pressure drops meaning that the air
pressure outside the lings is greater than the air pressure inside the lungs.
PULMONARY VENTILATION
This is the total volume of air that is moved into the lungfs in a minute.
Tidal Volume- the volume of air normally taken in for each breathe when the
body is at rest
Ventilation Rate- the number of breathes taken in one minute (normally 12-20)
Pulmonary Ventilation Rate= Tidal Volume x Ventilation
(dm3min-1) (dm3) (min-1)

3. Exchange of Gases in the Lungs
Alveoli
The site of gas exchange in mammals is the
epithelium of the alveoli.
The air sacs are very small at 100mm-
400mm each.
There are about 300 alveoli in each lung.
Each alveolus is lined with epithelial cells
0.05mm-0.3mm thick.
A network of pulmonary capillaries
surrounds each alveolus.
Oxygen passes into the alveolus and dissolves
in s small moist lining of the epithelial.
The moist lining also stops the alveolus from
drying and cracking and keeps the insides
lubricated.
The oxygen molecules diffuse into the blood
stream through the lining of the alveolus and
the capillaries. The red blood cell pick up the
oxygen and carries it to the heart by the
pulmonary vein.
Laws of Diffusion
The movement of the oxygen from the blood
to the cells also follows the laws of diffusion.
1) There is a high concentration within
the blood.
2) There is a low concentration within the cell.
3) Therefore the oxygen passes into the body cells.
Alveoli Adaptations
They are really good surface for gas exchange because:
1) Large surface area to volume ratio- speeds up the rate of exchange.
2) Thin exchange surface- SHORT diffusion pathway
3) Partially Permeable- Allows selected materials to diffuse easily.
4) Steep concentration gradient maintained by breathing and blood flow.
5) The walls are moist- allows oxygen to dissolve into liquid before diffusing.
6) Special liquid SURFACTANT- reduces surface tension and prevents air
sacs collapsing.

4. Pulmonary Tuberculosis:
Used to be called consumption.
Cause
Caused by a rod shaped bacterium:
1) Mycobacterium Tuberculosis
2) Mycobacterium Bovis
It is a slow growing organism (only divides every 16-20 hours)
Most commonly affects the lungs but can spread to other parts of the body.
Transmission
Spread through:
1) Droplet Infection such as sneeze, cough, laughing and talking
2) People with prolonged, frequent or intense contact are at highest risk.
3) Cows to Human mycobacterium BOVIS)
About 90% have asymptomatic latent TB that cannot be passed on.
There is a 10% lifetime chance that the latent infection will become active TB. If
untreated there is a more than 50% of dying.
Mycobacterium Bovis affects cattle. However they are regularly checked and
the milk is pasteurised which kills the bacterium.
Some groups are at greater risk at contracting TB:
1) Those in close contact with infected individuals
2) Those from the countries where TB is common.
3) Have reduced immunity such elderly people, AIDs sufferers, people with
medical conditions, homeless, alcoholics, drug users, etc.
Course of Infection
Bacteria grow and divide in the upper regions of the lungs.
Body’s immune system responds and white blood cells accumulate at the
infected area.
This leads to inflammation of the lungs and enlargement of the lymph nodes.
In a healthy person there are few symptoms and infection is controlled within
weeks.
However some bacteria still remains,
Many years later, the bacteria may re-emerge.
Bacteria can destroy the lung tissue, this results in cavities and scar tissue.
Suffers cough up damaged lung tissue and blood.
The TB can spread to the rest of the body if it’s not treated.
Treatment
Latent TB- usually single antibiotics.
Active TB- combinations of several antibiotics to reduce the bacterial growth.
Prevention
Children are vaccinated and those with TB are identified and treated.
Increase in TB in Eastern Europe and Africa due to AIDs epidemic causing
people to be more susceptible to TB.

5. Pulmonary Fibrosis
This is when scars form on the epithelium of the lungs causing them to become
irreversibly thickened.
Oxygen uptake will be less efficient because
1) The volume of air that the lung can contain reduces.
2) There is a grater diffusion pathway.
Fibrosis reduces the elasticity of the lungs so it is harder to breathe.
Shortness of breath-especially when exercising due to the amount of fibrous
tissues in the lungs.
1) Less air is taken in by each breath
2) Increased diffusion pathway due to the thickened epithelium
3) Loss of elasticity makes ventilation difficult and thus makes it hard to
maintain a diffusion gradient
Chronic, dry cough because the fibrous tissue creates an obstruction in the
airways of the lungs. The body naturally reacts to clear the obstruction by
coughing but as the tissue is immovable the cough is ‘dry’.
Pain and discomfort in the chest due to the pressure and damage from the
fibrous tissue and coughing.
Weakness and fatigue from reduced oxygen uptake. The energy released by
cellular respiration is reduced, leading to tiredness.
The exact cause is unclear, but evidence suggests that it is a reaction to
microscopic lung injury, to which some individuals are genetically more
susceptible.
Emphysema
Walls of the alveoli are broken down
Symptoms
1) Coughing, shortness of breath, and wheezing, developing into extreme
difficulty in breathing, bluish skin colour
2) Physical damage by repeated coughing and loss of elastin from walls of
alveoli. Less surface area is available for the exchange of gases
CAUSE
Smoking and air pollution
Treatment
Emphysema is irreversible
Asthma
Affects up to 10% of the worlds population.

6. 2000 deaths in UK each year.
Asthma tends to run in families – genetic element
Allergens include
1) Pollen, animal fur, faeces of house dust mite.
Can be triggered by
2) air pollutants(sulphur dioxide, nitrogen oxides and ozone), exercise, cold
air, infection, anxiety and stress.
3) Number of cases rising due to
4) Increase in air pollution
5) Increase in stress
6) Increase in the chemicals in our food
7) Cleaner lifestyle
The allergens cause the white blood cells lining the bronchi and bronchioles
to release histamine. This has the following effects:
a. Inflammation of the lining of the airways
b. Cells of the epithelial lining secrete larger quantities of mucus
c. Fluid leaves the capillaries and enters the airways
d. The muscle surrounding the bronchioles contracts ands so
constricts the airways
Overall there is a much greater resistance to the flow of air in and out of the
alveoli and therefore it is difficult to maintain the diffusion gradient.
Symptoms
Difficulty in breathing due to
1) Constriction of bronchi and bronchioles
2) Inflamed lining
3) Presence of additional mucus and fluid
Wheezing caused by air passing through constricted bronchi and bronchioles
Tight feeling in chest, a consequence of not being able to ventilate the lungs
properly
Coughing, a reflex response to the obstructed airways
Chronic Bronchitis
Having a productive cough for at least 3 months during 2 successive years
Symptoms:
Productive cough, breathlessness
Smoking and air pollution paralyse the cilia in the bronchial tubes so mucus
builds up in clumps that are coughed up (productive cough). The lining of the
bronchial tubes becomes irritated and inflamed.
Cause
Smoking and air pollution
Treatment
Drug treatment, oxygen therapy, and lung transplant
June 2013

7. Q3) ai) Name the process by which oxygen passes from an alveolus in the
lungs into the blood.
1) Diffusion
3aii) Describe 2 adaptions of the structure of alveoli for efficient gas
exchange.
1) Thin moist walls
2) Large Surface area
3b) People who have been fire-breathers for many years often find they
cannot breathe out properly. Explain why.
1) Loss of elasticity of the lungs
2) Scar Tissue
3) Less recoil
January 2013
1 (a) The diagram shows the structure of the human gas exchange system.
1) Trachea
2) Bronchus
1 (b) Explain how downward movement of the diaphragm leads to air
entering the lungs.
1. Increases the volume in the thorax
2. Lowers the pressure in the thorax
3. Pressure outside the lungs is greater so air is pushed inside.
1 c) Complete the equation.
Pulmonary ventilation = ...................................... × ........................................
1. Tidal Volume
2. Ventilation Rate
June 2012

8. 3a) Describe what happens to the diaphragm between times P and Q to
bring about the change in its shape.
1. Flattens
2. Contracts
3b) Air moves into the lungs between times P and Q. Explain how the
diaphragm causes this.
1. Diaphragm contracts and Flattens
2. Increases the volume in the thorax
3. Decreases the pressure inside the lungs.
4. Air moves from high to lower pressure.
3c) Describe how oxygen in air in the alveoli enters the blood in capillaries.
1. Oxygen diffuses into the capillary
2. Across as the alveoli’s’ epithelium and the capillary’s endothelium
January 2012
2a) The diaphragm helps to bring about the changes shown by the curve A.
Explain how.
1. Before his inhaler the Diaphragm was relaxed
2. The diaphragm was dome shaped
3. Which increased the pressure inside the lungs
4. Decreased the volume in the thorax.
2b) You could use curve A to find the total volume of air that this person
could breathe out in one complete breath. Describe how.
1. Extend the curve
2. Until the curve flattens and has reached a peak
3. You could use curve A to find the total volume of air that this person could
breathe out in one complete breath. Describe how.
2c) The inhaler which the person used contained a substance that dilates
bronchioles. Use this information to explain why curve A is different from
curve B.
1. Before the inhaler, the bronchioles were narrower.
2. The muscles around the bronchioles contracted.
3. Which causes less air to pass through making it harder to breathe
June 2011

9. 4a) The two people were breathing out during the time shown. What
evidence in the table supports this statement?
1. The volume of air in the lungs decreases.
4b) Calculate the rate at which person A breathed air out of his lungs
between 0 and 3 seconds. Show your working.
1. 6.5-2.3/3 secs = 4.2/3 = 1.4
4c) Person B has emphysema. Give one piece of evidence from the table
that shows this.
1. Reduces flow rates / less air breathed out / more air left in the lungs
4d) Emphysema reduces the efficiency of gas exchange in the lungs. Explain
why.
1. The alveoli breaks down which leaves fewer of them that are large
2. This increases the diffusion pathway
3. So less diffusion takes place
4. There is less elasticity in the lungs
5. Which reduced the flow rate
6. So a small concentration gradient.
January 2011
7a) Pulmonary tuberculosis is a disease of the lungs.
Describe the transmission and course of infection of pulmonary
tuberculosis.
1. Bacteria is transmitted by droplets from a sneeze or cough
2. The bacteria destroys the alveoli
3. Which leads to scar tissue and fibrosis
4. Damage leads to less diffusion as there’s an increased pathway
5. The bacteria could spread to other organs via bloodstream
7b) Emphysema is another disease of the lungs. People with emphysema
may feel weak and tired. Explain why.
1. The alveoli breaks down
2. Which increases the diffusion pathway so takes a longer time
3. Decreases the diffusion gradient
4. So less oxygen enters the blood
5. Less respiration takes place, which leaves the person tired.
June 2010

10. 2a) i) Explain how the graph shows that the person was breathing in
between times A and B.
1. The volume of air was increasing
ii) Describe and explain what happens to the shape of the diaphragm
between times A and B.
1. The diaphragm flattens
2. The muscle contracts
2b) The person’s pulmonary ventilation changed between times C and D.
Describe how the graph shows that the pulmonary ventilation changed.
1. Pulmonary ventilation= tidal volume x breathing rate
2. The breathing rate increases per minute.
3. The tidal volume increases between C and D as they are deeper breathes.
January 2010
2a) i) Describe the path by which oxygen goes from an alveolus to the
blood.
1. The oxygen diffuses across the epithelium of the alveolus
2. And through the epithelium of the capillary
2a) ii) Explain why people with miner’s lung have a lower concentration of
oxygen in their blood.
1. Longer Diffusion Pathway
2b) i) Describe how ventilation helps to maintain this difference in oxygen
concentration.
1. Brings in air that has a higher oxygen concentration.
2. Removes air with a lower oxygen concentration.
2b) ii) Give one other way that helps to maintain the difference in oxygen
concentration.
1. Circulation of blood
2c) Evaluate this conclusion.
1. Correlation does not prove causation, there may be other causes
2. Improved Diagnosis methods
3. Not all cases are reported. We don’t know the number of cases.