Biology · Unit 10

Lungs and Breathing

The respiratory system and gas exchange

Breathing and respiration are two different things, and this unit's first job is to separate them. Breathing is the mechanical business of moving air; respiration is the chemistry happening in every cell, whether you are breathing at that moment or not.

From there it covers the airway's anatomy, the mechanics that make air move without any muscle pulling on the lungs directly, and gas exchange at the alveoli - a surface area problem solved by making the surface very large and very thin.

This unit breaks down into 20 short steps and 120 questions, starting at difficulty 1 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 120
Difficulty: 1-3

What this unit covers

Respiratory Anatomy
Gas Exchange
Breathing Mechanism
Lung Function
Respiratory Health

Where this fits

Pairs with Heart and Circulation. Cell Transport and Energy explains what the oxygen is ultimately for.

Where people slip

Nothing pulls air into the lungs. The diaphragm changes the volume of the chest, pressure drops, and air moves in on its own - which is why a punctured chest wall stops the whole mechanism working.

How the unit is structured

Lungs and Breathing runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 3 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

Breathing Mechanism

Fill the blankLevel 1
1. The large, dome-shaped muscle found just below the lungs is the ____.
- diaphragmcorrect
- intercostal
- epiglottis
- bronchus
The diaphragm is the dome-shaped muscle beneath the lungs that changes the size of the chest as you breathe.
Multiple choiceLevel 1
2. Which muscle is the main muscle used for breathing?
- The diaphragmcorrect
- The heart
- The biceps
- The tongue
The diaphragm is a large sheet of muscle below the lungs, and it is the main muscle used for breathing.
Picture questionLevel 2
3. 🤧 This reflex is shown here. What does a sneeze mainly do?
- Forces air out to clear irritants from the nosecorrect
- Clears mucus from the deep bronchi
- Draws extra oxygen straight into the blood
- Warms the cold air entering the lungs
A sneeze forces a fast blast of air out through the nose to expel irritants such as dust or pollen from the nasal passages.
Put in orderLevel 2
4. Put these steps of breathing IN (inhalation) in the correct order.
Answer: Diaphragm contracts and flattens -> Ribcage moves up and out -> Chest volume increases -> Air pressure in the lungs drops -> Air is drawn into the lungs
When you inhale, the diaphragm contracts and flattens and the ribs move up and out, increasing chest volume, which lowers the pressure so air rushes in.
Fact or fibLevel 3
5. Breathing faster and more deeply than needed (hyperventilation) raises the carbon dioxide level of the blood.
Answer: False
Hyperventilation blows off extra CO2, so it actually lowers the blood carbon dioxide level.
Sequence recallLevel 3
6. Recall the order of the feedback response to rising carbon dioxide during activity.
Answer: Carbon dioxide rises in the blood -> Blood pH falls -> Chemoreceptors detect the change -> The medulla increases breathing rate and depth -> Carbon dioxide is removed and levels fall
Rising CO2 is detected through falling pH; the medulla increases ventilation, which removes CO2 and restores normal levels.

Gas Exchange

Build the sentenceLevel 1
7. Build the sentence that describes gas exchange in the alveoli.
Answer: Oxygen moves into the blood and carbon dioxide comes out
In the alveoli, oxygen moves into the blood while carbon dioxide moves out of the blood.
Fill the blankLevel 1
8. In the alveoli, gases move across the walls by a passive process called ____.
- diffusioncorrect
- digestion
- filtration
- breathing
Oxygen and carbon dioxide move by diffusion, from where they are more concentrated to where they are less concentrated.
Choose all that applyLevel 2
9. Which features make the alveoli good at exchanging gases? Select all that apply.
- A very large total surface areacorrect
- Walls that are only one cell thickcorrect
- Surrounded by many tiny blood capillariescorrect
- Covered in a thick, waterproof waxy layer
A large surface area, walls only one cell thick, and a rich blood supply all speed up diffusion; a thick waxy layer would slow it down.
Guess the numberLevel 2
10. Roughly how large is the total surface area of all the alveoli in a pair of adult lungs?
Answer: 70 square metres
The alveoli give the lungs a huge surface area of about 70 square metres, close to the size of a tennis court.
Fact or fibLevel 3
11. Carbon dioxide diffuses from the blood into the alveoli because its partial pressure is higher in the blood than in the alveolar air.
Answer: True
Deoxygenated blood carries a higher CO2 partial pressure than alveolar air, so CO2 diffuses out of the blood into the alveoli.
Match the pairsLevel 3
12. Match each gas exchange surface to the organism that uses it.
Answer: Alveolus = Mammal; Gill lamella = Fish; Tracheole = Insect; Spongy mesophyll = Leaf
Mammals use alveoli, fish use gill lamellae, insects use tracheoles, and leaves exchange gases through the air spaces of the spongy mesophyll.

Lung Function

Fact or fibLevel 1
13. Breathing and respiration mean exactly the same thing.
Answer: False
They are different: breathing moves air in and out of the lungs, while respiration is the chemical reaction that releases energy inside cells.
Guess the numberLevel 1
14. About how many breaths does a resting adult take in one minute?
Answer: 15 breaths per minute
A healthy adult at rest breathes roughly 12 to 18 times a minute, around 15 breaths per minute.
Fill the blankLevel 2
15. The maximum volume of air that can be breathed out after taking the deepest possible breath in is called the ____ capacity.
- vitalcorrect
- residual
- tidal
- functional
Vital capacity is the largest volume that can be exhaled after a maximal inhalation, equal to tidal volume plus the inspiratory and expiratory reserve volumes.
Multiple choiceLevel 2
16. Why does your breathing rate increase when you exercise?
- Muscles need more oxygen and produce more carbon dioxide to removecorrect
- To cool the blood down and nothing else
- Because the lungs shrink during exercise
- To slow the heart rate down
Exercising muscles need more oxygen for respiration and make more carbon dioxide, so you breathe faster to supply oxygen and remove the extra carbon dioxide.
Build the sentenceLevel 3
17. Build the equation that links the lung capacities.
Answer: total lung capacity equals vital capacity plus residual volume
Total lung capacity equals the vital capacity plus the residual volume.
Match the pairsLevel 3
18. Match each lung volume or capacity to its meaning.
Answer: Tidal volume = Air moved in one normal breath; Vital capacity = Most air exhaled after a full breath in; Residual volume = Air left in the lungs after full exhalation; Total lung capacity = Vital capacity plus residual volume
Tidal volume is one normal breath, vital capacity is the usable maximum, residual volume stays behind, and total lung capacity is vital capacity plus residual volume.

Respiratory Anatomy

Fact or fibLevel 1
19. Bronchioles are the smallest airways in the lungs, and they end in tiny air sacs.
Answer: True
Bronchioles are narrow tubes that branch off the bronchi and end in clusters of alveoli.
Fill the blankLevel 1
20. Each lung connects to the bottom of the trachea through a large airway called a ____.
- bronchuscorrect
- alveolus
- capillary
- cilium
The trachea splits into two bronchi, one leading into each lung.
Odd one outLevel 1
21. Which one of these is NOT part of the pathway that air travels through?
- Uretercorrect
- Trachea
- Bronchioles
- Alveoli
The ureter carries urine from the kidney to the bladder, so it is part of the urinary system, not the respiratory system.
Match the pairsLevel 2
22. Match each part of the respiratory system to its job.
Answer: Trachea = Carries air down towards the lungs; Alveoli = Where gas exchange happens; Diaphragm = Muscle that helps you breathe; Epiglottis = Flap that stops food entering the airway
Each structure of the respiratory system has a specific role in getting air to the blood.
Multiple choiceLevel 2
23. Why does the trachea have C-shaped rings of cartilage in its walls?
- To keep the airway open so it does not collapsecorrect
- To help digest food
- To warm the blood
- To make mucus for the stomach
The rings of cartilage hold the trachea open so it does not collapse as air is drawn in and out.
Choose all that applyLevel 3
24. Which of these are functions of the air-filled sinuses in the bones of the skull? Select all that apply.
- Making the skull lightercorrect
- Helping to warm and moisten inhaled aircorrect
- Adding resonance to the voicecorrect
- Producing red blood cells
The paranasal sinuses lighten the skull, help warm and moisten inhaled air, and add resonance to the voice; they do not make blood cells.

Respiratory Health

Fact or fibLevel 1
25. A reliever asthma inhaler works by widening the narrowed airways.
Answer: True
Reliever inhalers relax the muscles around the airways so they open up, making breathing easier during an attack.
Multiple choiceLevel 1
26. How do the airways trap dust and microbes in the air you breathe in?
- Sticky mucus traps them and cilia sweep them awaycorrect
- The alveoli swallow them
- The diaphragm burns them up
- Red blood cells eat them
Sticky mucus traps dust and microbes, and tiny hair-like cilia sweep the dirty mucus up and away from the lungs.
Build the sentenceLevel 2
27. Build the sentence that explains how the body acclimatises to living at high altitude over several weeks.
Answer: the body makes more red blood cells
To cope with low oxygen at altitude, the body makes more red blood cells so the blood can carry more oxygen.
Choose all that applyLevel 2
28. Select everything that increases when a person moves from rest to vigorous exercise.
- Breathing ratecorrect
- Depth of each breath (tidal volume)correct
- Minute ventilationcorrect
- Residual volume
- The need for surfactant falls to zero
Exercise raises breathing rate and tidal volume, so minute ventilation rises sharply, while residual volume is essentially unchanged.
Fill the blankLevel 3
29. Cystic fibrosis is caused by a faulty ____ ion channel (the CFTR protein), which makes the mucus lining the airways thick and sticky.
- chloridecorrect
- sodium
- calcium
- potassium
The CFTR protein normally moves chloride ions across cell membranes; when it is faulty, water balance is disturbed and the mucus becomes thick and sticky.
Match the pairsLevel 3
30. Match each respiratory disease to its description.
Answer: COPD = Long-term airway obstruction, usually from smoking, that makes breathing out hard; Pneumonia = Infection that fills the alveoli with fluid and pus; Cystic fibrosis = Inherited condition causing thick, sticky mucus in the airways; Tuberculosis = Bacterial lung infection spread through the air by coughing
COPD is long-term airway obstruction (often from smoking), pneumonia fills the alveoli with fluid, cystic fibrosis is an inherited mucus disorder, and tuberculosis is a bacterial infection spread through the air.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 17 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sequence recall
Sort into groups
Spell it
Tap the pairs
True or false
Type the answer

Practise Lungs and Breathing

120 questions across 20 steps. Start with step one and crawl at your own pace.

Play this unit

Read about Lungs and Breathing

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

How Your Lungs Exchange Oxygen and Carbon DioxideYour lungs move oxygen into the blood and carbon dioxide out of it. Tiny air sacs, thin surfaces and constant blood flow make this rapid exchange possible.July 29, 2026 · 5 min read

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