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GCSE Biology · GCSEChapter 7 · Lungs and gas exchange
GCSE · Chapter 7

Lungs and gas exchange

By the end of this chapter you will be able to

  • Name the parts of the airway and say what each does
  • Explain how alveoli are adapted for gas exchange
  • Describe how the chest muscles change the volume of the lungs when breathing in and out
  • Interpret data on smoking and lung disease, and describe the effect on the lungs
  • [H] Calculate the total surface area from the number and size of alveoli

You should already know

  • Diffusion and exchange surfaces (Chapter 3)
  • Aerobic respiration uses oxygen (Chapter 10 links back)

Where this leads

  • Blood and the circulation carry gases (Chapter 6)
  • Respiration in cells (Chapter 10)
  • Cancer and cell division (Chapter 4)

GCSE Biology. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Describe the structure of the lungs, trachea, bronchi and alveoli, Explain how alveoli are adapted for the diffusion of oxygen and carbon dioxide, Describe breathing, using the diaphragm and the intercostal muscles, and calculate changes in volume, Describe the effects of smoking and of lung disease (COPD and lung cancer) on the lungs, [H] Explain how the surface area of alveoli is related to gas exchange.

Exercise P  Do you remember?

1
FWhat is 0.5 multiplied by 10? Write the number.
2
FWhich gas do cells release from aerobic respiration? Write the words.
3
FWhat is the name for the movement of particles from high to low concentration, with no energy? Write the word.
4
FHow many cells thick is a capillary wall? Write the word.
5
FWhat is 40 percent of 50? Write the number.
7.1

The lungs and the airways

GCSE
Describe the structure of the lungs, trachea, bronchi, bronchioles and alveoli
Video lesson: The lungs and the airwaysComing soon
Context. Ali coughs after a run. “My throat is full of mucus,” he says. The coughing clears the airway. Air has to travel a long way from the nose to the tiny sacs where gas exchange happens, and the airway is built to keep it clean.

Air enters through the nose or mouth, then passes down the trachea (windpipe). The trachea splits into two bronchi, one for each lung. The bronchi split into smaller tubes called bronchioles, which end in clusters of tiny air sacs called alveoli.

The trachea and bronchi are lined with ciliated cells and goblet cells. The goblet cells make mucus, which traps dust and microorganisms. The cilia are tiny hairs that move the mucus up the airway, so it can be swallowed or coughed out.

trachea (windpipe)bronchusalveoli: tiny air sacslung
Trachea, bronchi and lungs, with clusters of alveoli

Key ideas

  • Trachea: windpipe, lined with mucus-making goblet cells and cilia.
  • Bronchi and bronchioles: smaller airways that carry air to the alveoli.
  • Alveoli: tiny air sacs where gas exchange happens.
  • Mucus traps dust and microorganisms; cilia move the mucus up and out.
Worked example 7.1.1
Name the tube that carries air from the nose and mouth into the chest. Write the word.

Method. Recall the first tube of the airway.

  1. Recall. The trachea is the windpipe that carries air down into the chest.
    windpipe
  2. Name it. So the tube is the trachea.
    trachea
  3. Write the answer.
    trachea

Check. The trachea splits into two bronchi. ✓

Worked example 7.1.2
Name the tiny air sacs where gas exchange happens. Write the word.

Method. Recall the gas exchange sacs.

  1. Recall. Gas exchange happens in tiny air sacs at the ends of the bronchioles.
    air sacs
  2. Name them. These sacs are the alveoli.
    alveoli
  3. Write the answer.
    alveoli

Check. Alveoli are at the ends of the bronchioles. ✓

Worked example 7.1.3
Name the cells in the airway that move the mucus, and say what moves it. Write the words.

Method. Recall the cells and what they do.

  1. Recall. The cilia are tiny hairs on the ciliated cells that move the mucus.
    move the mucus
  2. Name them. So the cells are ciliated cells, and the hairs are cilia.
    ciliated cells
  3. Write the answer.
    ciliated cells; cilia

Check. Goblet cells make the mucus. ✓

Watch out

Watch out: the trachea does not carry gas exchange. Gas exchange happens in the alveoli, at the very end of the airway.

Exam tip

Exam tip. Name the part of the airway and what it does. For a mucus question, mention both the goblet cells and the cilia.

Try it (with your teacher). With your teacher, look at a labelled diagram of the airway. Trace the path of one breath of air from the nose to the alveoli, naming each part.

Exercise 7A  The lungs and the airways

1
FName the tube that splits into two bronchi. Write the word.
2
FName the smaller tubes that branch from the bronchi. Write the word.
3
FName the cells that make mucus. Write the words.
4
FWhat do the cilia do? Write the words.
5
FWhat does mucus trap in the airway? Write the words.
6
FName the tiny air sacs at the ends of the bronchioles. Write the word.
7
FPut these in order from the outside air to the alveoli: bronchi, trachea, bronchioles. Write the order.
8
FIs the trachea lined with goblet cells? Write yes or no.
9
PSA pupil says the alveoli are in the trachea. Write yes or no, and give one reason. Accept any answer that says the alveoli are at the ends of the bronchioles, not in the trachea.
10
PSWhy is mucus useful in the airway? Write one sentence. Accept any sentence that says it traps harmful particles, so they can be removed by cilia and coughing.
11
PSAli coughs to clear his airway. Name the reflex action that clears the airway, and say what it does. Write the words. Accept coughing, which clears mucus and particles.
12
RChallenge: explain why the air passages are branched into so many small tubes, in two sentences. Accept any answer that says the many branches give a large number of small air sacs, and so a large surface for gas exchange.
7.2

Alveoli and gas exchange

GCSE
Explain how alveoli are adapted for diffusion, Describe how oxygen and carbon dioxide are exchanged
Video lesson: Alveoli and gas exchangeComing soon
Context. Priya looks at a diagram of an alveolus wrapped in blood capillaries. “Oxygen goes into the blood and carbon dioxide comes out,” her teacher says. “How does it happen so well in such a small space?”

Oxygen diffuses from the air in the alveolus into the blood in the capillaries. Carbon dioxide diffuses the other way, from the blood into the air in the alveolus, to be breathed out. Both gases move down their concentration gradients by diffusion, so no energy is needed.

Alveoli are adapted for this exchange: they have a very large surface area, walls only one cell thick, and a good blood supply that keeps the concentration gradient steep.

airO2 inCO2 outalveolus with its capillary (one cell thick walls)the blood in the capillary carries oxygen away and brings carbon dioxide
An alveolus with its capillary, showing oxygen in and carbon dioxide out
FeatureHow it helps diffusion
very many tiny alveolia large surface area for gas exchange
walls one cell thicka short distance for gases to diffuse
surrounded by capillariesa good blood supply keeps the concentration gradient steep
moist lininggases dissolve before they diffuse
How the alveoli are adapted for gas exchange

Key ideas

  • Oxygen diffuses from the alveolus into the blood; carbon dioxide diffuses out.
  • Alveoli have a large surface area, thin walls, and a good blood supply.
  • A good blood supply keeps the concentration gradient steep.
  • Gases dissolve in the moist lining before they diffuse.
Worked example 7.2.1
Name the gas that diffuses from the alveolus into the blood. Write the word.

Method. Recall the gas needed by the cells.

  1. Recall. Cells need oxygen for aerobic respiration, so it moves into the blood.
    moves into the blood
  2. Name it. So the gas is oxygen.
    oxygen
  3. Write the answer.
    oxygen

Check. Carbon dioxide moves the other way. ✓

Worked example 7.2.2
Name two adaptations of alveoli for diffusion. Accept any two of: large surface area, thin walls, good blood supply.

Method. Recall the adaptations.

  1. Recall. Alveoli have a large surface area, thin walls and a good blood supply.
    large surface area
  2. Choose two. Any two of these are correct.
    any two
  3. Write the answer.
    Accept any two of: large surface area, thin walls, good blood supply.

Check. Each adaptation speeds up diffusion. ✓

Worked example 7.2.3
Explain why a good blood supply helps gas exchange. Write one sentence.

Method. Think about the concentration gradient.

  1. Think. The blood carries oxygen away and brings carbon dioxide.
    carries oxygen away
  2. Conclude. So the gradient stays steep, and diffusion continues.
    stays steep
  3. Write the answer.
    The blood carries oxygen away and brings carbon dioxide, so the concentration gradient stays steep.

Check. A steep gradient speeds up diffusion. ✓

Watch out

Watch out: both gases move by diffusion in the same place. Oxygen goes into the blood, and carbon dioxide goes out of the blood, so do not say that one moves by active transport.

Exam tip

Exam tip. When you explain an adaptation, say what it does and why that helps. “Thin walls” alone does not earn the mark.

Try it (with your teacher). With your teacher, look at a labelled diagram of an alveolus. Draw it, and add arrows for oxygen and carbon dioxide, with a label for each adaptation.

Exercise 7B  Alveoli and gas exchange

1
FWhich gas moves from the alveoli into the blood? Write the word.
2
FWhich gas moves from the blood into the alveoli to be breathed out? Write the words.
3
FName the process by which gases move into and out of the alveoli. Write the word.
4
FName one feature of alveoli that gives a large surface area. Write the words. Accept many alveoli, or a very large number of tiny sacs.
5
FWhat is the thickness of the alveolus wall? Write the words.
6
FWhich vessels surround the alveoli? Write the word.
7
FDoes gas exchange in the alveoli need energy from respiration? Write yes or no.
8
PSName the layer of the alveolus that keeps gases moist, so they can dissolve before diffusing. Write the words. Accept the moist lining.
9
PSExplain why oxygen moves into the blood even though the blood already contains some oxygen. Write one sentence. Accept any sentence that says the blood is constantly carried away, so its oxygen level stays lower than the alveolus.
10
PSA pupil says alveoli have thick walls to protect the lungs. Explain why this is not correct, in one sentence. Accept any sentence that says the walls are thin, so the distance for diffusion is short.
11
RChallenge: explain why alveoli are not just a large surface but also need a good blood supply. Write two sentences. Accept any answer that says the blood supply carries gases away, keeping the gradient steep, and replaces the blood so exchange continues.
7.3

Breathing and ventilation

GCSE
Describe breathing in and out, using the diaphragm and the intercostal muscles, Calculate changes in lung volume
Video lesson: Breathing and ventilationComing soon
Context. Hana lies on the floor and places her hand on her belly. “It rises when I breathe in,” she says. Her teacher explains that a muscle under the lungs is doing the work, and the ribs help too.

Breathing in (inhalation): the diaphragm contracts and flattens, and the intercostal muscles between the ribs contract, lifting the ribs up and out. The volume of the chest increases, so the pressure falls and air flows in.

Breathing out (exhalation): normally this is passive. The diaphragm relaxes and domes up, and the intercostal muscles relax, so the ribs move down and in. The volume decreases, the pressure rises, and air flows out.

breathing in (inhale)diaphragm flattens (down)ribs move up and out; volume increasesbreathing out (exhale)diaphragm domes (up)ribs move down and in; volume decreases
Breathing in and breathing out, with the diaphragm and ribs
Lung volume during normal breathing (invented data)012340123456time (seconds)volume (dm3)
Lung volume during normal breathing (invented data)

Key ideas

  • Breathing in: the diaphragm flattens and the ribs move up and out.
  • Breathing out: the diaphragm domes up and the ribs move down and in.
  • When the volume increases, the pressure falls and air flows in.
  • Breathing out at rest is passive; it needs no muscle contraction.
Worked example 7.3.1
Name the muscle below the lungs that flattens when you breathe in. Write the word.

Method. Recall the muscle under the lungs.

  1. Recall. The diaphragm is the muscle below the lungs that contracts when breathing in.
    below the lungs
  2. Name it. So the muscle is the diaphragm.
    diaphragm
  3. Write the answer.
    diaphragm

Check. The intercostal muscles are between the ribs. ✓

Worked example 7.3.2
Read the graph. What is the volume at 3 seconds? Write the number, in dm3.

Method. Find 3 seconds on the time axis, then read the volume.

  1. Find 3. Find 3 seconds on the x-axis.
    3 s
  2. Read. The volume at 3 seconds is 3.4 dm3.
    3.4
  3. Write the answer.
    3.4

Check. 3.4 is the highest value in the graph. ✓

Worked example 7.3.3
Find the change in volume from 0 to 3 seconds. Write the number, in dm3.

Method. Subtract the volume at 0 seconds from the volume at 3 seconds.

  1. Read. The volume is 2.5 dm3 at 0 seconds and 3.4 dm3 at 3 seconds.
    2.5 and 3.4
  2. Subtract. The change is 3.4 - 2.5 = 0.9 dm3.
    3.4 - 2.5 = 0.9
  3. Write the answer.
    0.9

Check. 2.5 + 0.9 = 3.4. ✓

Watch out

Watch out: breathing in is active (muscles contract), but breathing out at rest is passive (muscles relax). Do not say that the diaphragm pushes air out at rest.

Exam tip

Exam tip. When you describe breathing in, say which muscle contracts and what happens to the volume and pressure.

Try it (with your teacher). Lie on your back with your hands on your ribs and belly. Breathe in gently, then out. Describe in one sentence what happens to your ribs and your belly. Do not hold your breath.

Exercise 7C  Breathing and ventilation

1
FName the muscle that contracts and flattens when you breathe in. Write the word.
2
FName the muscles between the ribs that help with breathing. Write the words.
3
FWhen you breathe in, do the ribs move up and out, or down and in? Write the words.
4
FWhen you breathe in, does the volume of the chest increase or decrease? Write the word.
5
FWhen you breathe in, does the pressure inside the chest rise or fall? Write the word.
6
FIs breathing out at rest an active or a passive process? Write the word.
7
FIn normal breathing, what is the volume at 0 seconds in the graph? Write the number, in dm3.
8
FWhat is the lowest volume shown in the graph? Write the number, in dm3.
9
PSFind the change in volume from 3 seconds to 6 seconds. Write the number, in dm3.
10
PSDescribe what happens to the volume of the lungs when a person breathes out, in one sentence. Accept any sentence that says the volume decreases as the diaphragm domes up and the ribs move down and in.
11
PSExplain why air flows into the lungs when a person breathes in. Write one sentence. Accept any sentence that says the volume increases, so the pressure falls below the outside pressure, and air moves in.
12
RChallenge: a student says the diaphragm pulls the air into the lungs. Explain why this is not quite correct. Write two sentences. Accept any answer that says the muscle changes the volume of the chest, and the pressure difference moves the air in.
7.4

Smoking and lung disease

GCSE
Describe the effects of smoking on the lungs, Describe COPD and lung cancer, Interpret data on smoking and lung disease
Video lesson: Smoking and lung diseaseComing soon
Context. Dan’s older cousin has started smoking. Dan finds a leaflet that says “smoking damages the lungs” and asks his science teacher what this means. The teacher shows him a graph of data from a group of people, which he must read carefully.

Smoking damages the lungs in several ways. Tar from the smoke coats the alveoli and the airways, and the cilia are paralysed and killed, so mucus builds up and cannot be cleared. Carbon monoxide binds to haemoglobin, reducing the amount of oxygen that the blood can carry. Smoking can lead to COPD (chronic obstructive pulmonary disease), which narrows the airways and damages the alveoli, and to lung cancer, when cells in the lungs divide uncontrollably.

Cigarettes per day (invented data)Lung disease cases per 100 people
01
53
106
2012
Lung disease and cigarettes smoked per day (invented data for practice)
Lung disease cases per 100 people (invented data)02468101214051020cigarettes per daycases per 100
Bar chart of lung disease cases per 100 people, by cigarettes smoked per day (invented data)
DiseaseWhat happens to the lungsLink to smoking
COPD (chronic obstructive pulmonary disease)airways are narrowed; alveoli are damageda major cause
lung cancercells in the lungs divide uncontrollablya major cause
emphysema (part of COPD)alveolar walls break down, so the surface area is reduceda major cause
Two lung diseases and their links to smoking

Key ideas

  • Tar coats the airways and alveoli, and damages the cilia.
  • Carbon monoxide reduces the amount of oxygen the blood carries.
  • COPD narrows the airways and damages the alveoli.
  • Lung cancer is uncontrolled cell division in the lungs.
Worked example 7.4.1
Read the bar chart. How many cases per 100 people are there for 20 cigarettes a day? Write the number.

Method. Find the bar for 20 cigarettes.

  1. Find. The bar for 20 cigarettes a day is the tallest bar.
    tallest bar
  2. Read. It shows 12 cases per 100 people.
    12
  3. Write the answer.
    12

Check. The table gives the same figure. ✓

Worked example 7.4.2
Find how many more cases there are per 100 people at 20 cigarettes a day than at 0. Write the number.

Method. Subtract the two counts.

  1. Read. There are 12 cases at 20 cigarettes and 1 at 0.
    12 and 1
  2. Subtract. The difference is 12 - 1 = 11 cases per 100 people.
    12 - 1 = 11
  3. Write the answer.
    11

Check. 1 + 11 = 12. ✓

Worked example 7.4.3
Name the disease in which the airways are narrowed and the alveoli are damaged. Write the words.

Method. Recall the disease.

  1. Recall. COPD narrows the airways and damages the alveoli.
    narrows the airways
  2. Name it. So the disease is chronic obstructive pulmonary disease (COPD).
    COPD
  3. Write the answer.
    chronic obstructive pulmonary disease (COPD)

Check. COPD is linked to smoking. ✓

Watch out

Watch out: the data show an association between smoking and lung disease, not a proof on their own. The data are invented here, and you must always say what the data do and do not show.

Exam tip

Exam tip. When you read a data set, quote one value from the table or graph. Say what it shows, then how far it supports the conclusion.

Try it (with your teacher). With your teacher, find out how a block of cards with a mock tar stain would affect a model of the airway. Do not use real tobacco. Describe what the model shows.

Exercise 7D  Smoking and lung disease

1
FWhich substance from cigarette smoke coats the airways and alveoli? Write the word.
2
FWhich gas from smoking binds to haemoglobin and reduces the oxygen carried by the blood? Write the words.
3
FWhat does smoke do to the cilia in the airways? Write the words.
4
FName the disease that narrows the airways and damages the alveoli. Write the letters.
5
FWhat does lung cancer involve, in terms of cell division? Write the words.
6
FIn the table, how many cases per 100 people are there for 10 cigarettes a day? Write the number.
7
PSHow many more cases per 100 people are there at 5 cigarettes a day than at 0? Write the number.
8
PSDoes the bar chart show that the number of cases rises as the number of cigarettes rises? Write yes or no.
9
PSA pupil says smoking causes lung cancer for every smoker. Write yes or no, and give one reason. Accept any answer that says the data show an association, and not every smoker gets the disease.
10
PSExplain why smoking reduces the amount of oxygen available to the body. Write one sentence. Accept any sentence that says carbon monoxide binds to haemoglobin, so less oxygen is carried.
11
RChallenge: explain why a smoker who develops COPD may have difficulty breathing out, in two sentences. Accept any answer that says the airways are narrowed, and the alveoli damaged, so air is trapped and cannot be breathed out easily.
7.5

Alveolar surface area and gas exchange [H]

GCSE
[H] Calculate the total surface area of alveoli from invented counts and sizes, [H] Explain the link between surface area and exchange
Video lesson: Alveolar surface area and gas exchange [H]Coming soon
Context. Ali asks how many alveoli there are in a lung, and how much surface they have altogether. His teacher gives a simple practice problem with invented numbers, so the method can be learned before real data are used.

[H] Higher tier only. This section is higher-tier content. It uses invented numbers for practice, to show how the surface area of many small sacs adds up.

The total surface area of the alveoli is found by multiplying the number of alveoli by the surface area of one alveolus. Many small sacs give a very large total area, which is what the lungs need for gas exchange.

Because the alveoli are so small and so many, the total surface area is far larger than the body surface. This is why the lungs can take in enough oxygen for the whole body.

FeatureHow it helps diffusion
very many tiny alveolia large surface area for gas exchange
walls one cell thicka short distance for gases to diffuse
surrounded by capillariesa good blood supply keeps the concentration gradient steep
moist lininggases dissolve before they diffuse
Adaptations of alveoli for gas exchange

Key ideas

  • [H] Total surface area = number of alveoli x surface area of one alveolus.
  • [H] Many small alveoli give a large total surface area.
  • [H] A larger surface area allows more diffusion in a given time.
  • [H] The surface area is limited by disease: damaged alveoli have less surface.
Worked example 7.5.1
[H] There are 200 alveoli, and each has a surface area of 4 mm2. Find the total surface area in mm2. Write the number.

Method. Multiply the number of alveoli by the area of one alveolus.

  1. Multiply. Total = 200 x 4.
    200 x 4
  2. Calculate. 200 x 4 = 800 mm2.
    800
  3. Write the answer.
    800

Check. 800 divided by 200 is 4 mm2. ✓

Worked example 7.5.2
[H] If damage halves the number of alveoli from 200 to 100, what is the new total surface area, if each alveolus still has 4 mm2? Write the number.

Method. Recalculate with the new number of alveoli.

  1. New number. The number of alveoli is now 100.
    100
  2. Calculate. New total = 100 x 4 = 400 mm2.
    400
  3. Write the answer.
    400

Check. Half the alveoli gives half the total area. ✓

Worked example 7.5.3
[H] Explain why damaged alveoli reduce gas exchange. Write one sentence.

Method. Think about the surface area.

  1. Think. Damage reduces the number of alveoli and the surface area.
    reduces the surface area
  2. Conclude. Less surface means less diffusion of oxygen and carbon dioxide.
    less diffusion
  3. Write the answer.
    Damage reduces the surface area, so less oxygen and carbon dioxide can diffuse.

Check. A smaller surface means slower diffusion. ✓

Watch out

Watch out: a bigger total surface area is the result of many small alveoli, not one big one. Do not multiply the number of alveoli by the area of the whole lung.

Exam tip

Exam tip. [H] Check the units of the final answer. An area in mm2 stays in mm2 when you multiply by a number of alveoli.

Try it (with your teacher). With your teacher, use a drawing of a sponge or a bunch of grapes to show how many small pieces give a large total surface. Describe what happens to the total surface if the pieces are made larger.

Exercise 7E  [H] Alveolar surface area and gas exchange

1
F[H] Write the formula for the total surface area of the alveoli. Write the words.
2
F[H] There are 50 alveoli, each with an area of 2 mm2. Find the total area in mm2. Write the number.
3
F[H] There are 200 alveoli, each with an area of 4 mm2. Find the total area in mm2. Write the number.
4
PS[H] If there are 300 alveoli, each with an area of 3 mm2, find the total area in mm2. Write the number.
5
PS[H] Find the total area if there are 200 alveoli, each with an area of 4 mm2, and 100 of them are damaged and lose their area. Write the number in mm2. Accept 400.
6
R[H] Explain why many small alveoli have a larger total surface area than one large alveolus with the same total volume. Write one sentence. Accept any sentence that says the small sacs give more surface for the same space.
7
PS[H] A pupil says the total surface area of the alveoli is the same as the surface area of one alveolus. Write yes or no, and give one reason. Accept any answer that says there are many alveoli, so the total is many times larger.
8
R[H] Challenge: explain why a fall in the number of alveoli caused by emphysema reduces the rate of oxygen uptake. Write two sentences. Accept any answer that says less surface area means less diffusion, so less oxygen reaches the blood.

Chapter summary

SkillMethod
AirwayTrachea, bronchi, bronchioles, alveoli; goblet cells make mucus and cilia move it.
AlveoliLarge surface area, walls one cell thick, a good blood supply and a moist lining.
Breathing inDiaphragm flattens and ribs move up and out; volume increases; pressure falls.
Breathing outDiaphragm domes up and ribs move down and in; volume decreases; pressure rises.
SmokingTar damages the airways and cilia; carbon monoxide reduces oxygen carried by the blood.
COPD and lung cancerCOPD narrows the airways and damages the alveoli; lung cancer is uncontrolled cell division.
[H] Surface areaTotal = number of alveoli x surface area of one alveolus.

Can you…?

  • I can name the parts of the airway and say what each does
  • I can explain how alveoli are adapted for gas exchange
  • I can describe breathing in and out, using the diaphragm and intercostal muscles
  • I can interpret data on smoking and lung disease
  • [H] I can calculate a total surface area from the number and size of alveoli

Key terms

trachea
the windpipe, which carries air to the bronchi
bronchus
one of the two tubes that carry air into each lung
bronchiole
a small airway that ends in alveoli
alveolus
a tiny air sac in the lungs where gas exchange happens
cilia
tiny hairs that move mucus up the airway
goblet cell
a cell that makes mucus in the airway
diaphragm
a muscle below the lungs that changes the volume of the chest
intercostal muscles
muscles between the ribs that move the ribs when breathing
COPD
chronic obstructive pulmonary disease, which narrows the airways and damages the alveoli
[H] total surface area
the number of alveoli multiplied by the surface area of one alveolus

Exercise 7Z  Check-up

1
Name the tube that carries air from the nose into the chest. Write the word.
2
Name the tiny air sacs where gas exchange happens. Write the word.
3
Name the muscle below the lungs that contracts when you breathe in. Write the word.
4
Which gas diffuses from the blood into the alveoli? Write the words.
5
Name the disease in which the airways are narrowed and the alveoli are damaged. Write the letters.
6
Name one adaptation of alveoli for gas exchange. Accept any one: a large surface area, thin walls, or a good blood supply.
7
What is the volume of the lungs at 3 seconds in the breathing graph? Write the number, in dm3.
8
A group of 40 smokers has 12 with lung disease. Find the percentage. Write the number, with the percentage sign.
9
Explain in one sentence what happens to the chest volume when you breathe out. Accept any sentence that says the volume decreases as the diaphragm domes up and the ribs move down and in.
10
Explain why cilia and goblet cells are important in the trachea. Write one sentence. Accept any sentence that says goblet cells make mucus that traps particles, and cilia move it away from the lungs.

Total 24 marks. Allow about 24 minutes.

Exercise 7X  Exam-style questions

1
FName the process by which oxygen moves from the alveoli into the blood. Write the word.[1 mark]
2
FName the muscle that relaxes and domes up when you breathe out at rest. Write the word.[1 mark]
3
FName the lung disease caused by uncontrolled cell division in the lungs. Write the words.[1 mark]
4
FDescribe two adaptations of alveoli for gas exchange. Accept any two of: a large surface area, thin walls, a good blood supply, a moist lining.[2 marks]
5
FDescribe the process of breathing in, naming the muscles and the change in volume. Write three points. Accept any three of: the diaphragm contracts and flattens; the intercostal muscles contract; the ribs move up and out; the volume increases; the pressure falls.[3 marks]
6
RExplain how smoking causes COPD. Write three points. Accept any three of: tar coats and damages the airways; cilia are damaged and mucus builds up; the airways narrow; the alveoli are damaged.[3 marks]
7
PSIn the invented data, the bar for 10 cigarettes a day is 6 and for 20 cigarettes a day is 12. Work out how many times greater the number of cases is at 20 cigarettes. Write the number.[2 marks]
8
PSA pupil finds that the volume of the lungs changes from 2.5 dm3 to 3.4 dm3 in one breath. Calculate the change in volume, and say whether this is a breath in or a breath out. Accept 0.9 dm3, breath in.[2 marks]
9
RInvented data: 0 cigarettes a day, 1 case per 100 people; 5 a day, 3 cases; 10 a day, 6 cases; 20 a day, 12 cases. Describe the evidence from these data about smoking and lung disease, and say what the data cannot prove. Accept any answer that says the cases rise with cigarettes per day, but the data show an association and cannot prove that smoking alone causes the disease.[4 marks]
10
R[H] A lung has 300 alveoli, each with a surface area of 3 mm2. Find the total surface area. Explain how damage to the alveoli would change this total. Accept 900 mm2, and an answer that says damage reduces the number of alveoli, so the total surface falls.[5 marks]
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