KS3 · Biology

Smoking and the gas exchange system

A cigarette looks like one small thing. Burn it and it releases thousands of chemicals, and they head for different places: your airways, your lungs, your blood and your heart.

Build the web

Where does each part of the smoke do its damage?

Three of these are harmful things in cigarette smoke: nicotine, tar and carbon monoxide. The other four are things they can lead to. Make a link for every arrow you think is real: choose what acts, then what it acts on. Two clues. Some routes pass through a middle step before they reach a disease. And one disease can be reached by more than one road. Have a go, then compare with the lesson's web.

  1. Nicotine
  2. Tar
  3. Carbon monoxide
  4. COPD: alveoli walls break down
  5. Less oxygen in the blood
  6. Heart disease (outcome)
  7. Cancer
Add a link

No links yet.

The fourth harm: smoke and heat

?

Reason it through

Where does smoker's cough come from?

Link 1 of 4

First link · your turn

Your airways are lined with ciliated cells. What do healthy ones do for you?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Inside the lungs: what COPD does to the alveoli

Healthy alveolivsAlveoli damaged in COPD (such as emphysema)

Compare the two columns first, then open each insight.

Focus

Alveoli walls

Healthy alveoli

Intact

Alveoli damaged in COPD (such as emphysema)

Broken down

The insight

This is the difference that matters. In COPD, the walls of the alveoli break down.

Surface area for gas exchange

Healthy alveoli

The full surface area

Alveoli damaged in COPD (such as emphysema)

A smaller surface area

What caused the damage

Healthy alveoli

No damage from tar

Alveoli damaged in COPD (such as emphysema)

Tar from cigarette smoke

What do you think?

Only a few, and they'd stop if they knew?

First, the basics. Tobacco is the dried leaves of the tobacco plant, rolled into cigarettes or cigars. Smoking means breathing in and out the smoke from burning it. Now, Jay says: "My uncle only has a few cigarettes a day, so he's basically fine. And if he really knew how bad smoking was, he'd just stop."

Which idea is closest to what you think right now?
How sure are you?

Your turn to explain

Follow one route all the way

Explain how carbon monoxide in cigarette smoke can lead to heart disease. [5 marks]

0 words · your answer stays on this page and is not sent anywhere.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

One cigarette, several separate routes to disease

What you need to know

  • Smoking means breathing in and out the smoke from burning tobacco, which is the dried leaves of the tobacco plant.
  • Burning tobacco releases thousands of different chemicals, some of which cause cancer. There is no safe level of smoking.
  • Four parts of smoking do harm: nicotine, tar, carbon monoxide, and the smoke and heat.
  • Smoking increases the risk of asthma, lung infections such as bronchitis, COPD, lung cancer and heart disease.

The big picture

Cigarette smoke isn't one harm, it's several. Nicotine, tar, carbon monoxide, and the smoke and heat themselves each take their own route through the body, damaging the airways, the alveoli, the blood and the heart. Some of those routes end at the same disease. Nicotine is highly addictive, which is why people keep smoking even when they know the risks, and there is no safe level of smoking.

Key points

1Nicotine is a highly addictive drug. Addiction is a persistent urge to use a drug, which is why people keep smoking even when they know it's harmful.
2Nicotine can narrow the coronary arteries, cutting the oxygen reaching the heart muscle, and can raise blood pressure and heart rate, which strains and can damage blood vessels.
3The chemicals in tar damage DNA, which can lead to uncontrolled cell division: cancer of the mouth, throat or lungs.
4Tar also damages the alveoli: their walls break down, giving a smaller surface area for gas exchange. This is COPD, such as emphysema.
5Carbon monoxide diffuses into the blood through the alveoli and takes the place of oxygen in red blood cells.
6Carbon monoxide and COPD both reduce the oxygen in the blood, so the circulatory system has to work harder, which can lead to heart disease.
7Smoke and heat damage the ciliated cells lining the airways, so mucus isn't removed effectively and the smoker has to cough: smoker's cough.

Worked example

Problem

Explain how the tar in cigarette smoke can cause lung cancer.

⚠ Watch out

Mixing up which part of the smoke does what. Tar causes cancer and COPD. Carbon monoxide takes the place of oxygen in red blood cells. Nicotine is the addictive one that also acts on the heart. Smoke and heat damage the ciliated cells.

🧠

Memory hook

Nicotine Narrows, Tar Tears, Carbon monoxide Crowds out. Nicotine narrows the coronary arteries, tar tears down the alveoli walls (and damages DNA), and carbon monoxide crowds oxygen out of the red blood cells. And the heat? It hits the ciliated cells first.

✓

Check yourself

Without looking back: name the four harmful parts of smoking, say where each one does its damage, and explain why carbon monoxide and COPD end up at the same disease.

Flashcards

(13)
What is tobacco, and what does 'smoking' mean?
Tobacco is the dried leaves of the tobacco plant, rolled into cigarettes or cigars. Smoking is breathing in and out the smoke from burning tobacco.
Is there a safe level of smoking?
No. Burning tobacco releases thousands of different chemicals, and some of them cause cancer.
What is nicotine, and why do people keep smoking?
A highly addictive drug found in tobacco leaves. Addiction is a persistent urge to use a drug, so people carry on even when they know it's harmful.
How can nicotine affect the coronary arteries?
It can narrow them. Less oxygen then reaches the heart's muscle cells for respiration, and if a large part of the heart is damaged this can cause a heart attack.
How can nicotine affect blood pressure, and why does that matter?
It can raise blood pressure and heart rate. High blood pressure strains the blood vessels and can damage them, which can lead to heart disease.
What do healthy ciliated cells in the airways do?
They trap dirt and dust, which helps protect us from infections.
What causes smoker's cough?
Smoke and heat damage the ciliated cells, so they can't remove mucus effectively. The smoker has to cough to move it.
Which cancers can the tar in cigarette smoke cause?
Cancers of the mouth, throat and lungs.
What does COPD stand for? Give one example.
Chronic obstructive pulmonary disease. Emphysema is one example.
What happens to the alveoli in COPD?
Tar damages them and their walls break down, leaving a smaller surface area for gas exchange.
What does carbon monoxide do once it's breathed in?
It diffuses into the blood through the alveoli and takes the place of oxygen in the red blood cells.
What do carbon monoxide and COPD have in common?
Both reduce the amount of oxygen in the blood, so the circulatory system has to work harder. This can lead to heart disease.
Name diseases that smoking increases the risk of.
Asthma, lung infections such as bronchitis, COPD, lung cancer and heart disease.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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How this lesson was checked. This KS3 Biologylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.