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SavannahYear 8
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ScienceBreathing and digestion30 min★★★ difficulty

Breathing, gas exchange and what damages it

Breathing and respiration are not the same thing. Breathing moves air; gas exchange swaps oxygen and carbon dioxide across a surface thinner than tissue paper. This lesson gets that surface clear in your head.

Part of your national curriculum
  • Biology: structure and function: Understand the structure and functions of the gas exchange system and the effects of exercise, asthma and smoking

Lesson overview

What you'll learn in this lesson

Understand the structure and functions of the gas exchange system and the effects of exercise, asthma and smoking

Key learning points

  • • Getting air in
  • • The exchange surface
  • • Exercise
  • • Asthma and smoking

This lesson at a glance

  • 30 minutes
  • 18 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

structurefunctionsexchangesystemeffects

Scroll down — the lesson carries on below

Part 1 of 18 · Discover6%
1

Watch & discover

Part 1 of 18

Watch first

Breathing, gas exchange and what damages it

An English teaching video on this topic from Amoeba Sisters. Watch it, then scroll down for the lesson.

Do it for real

The practicals below use what the film shows, with a full method you can follow at home.

How fast does exercise change your breathing?Does chewing start digestion before you swallow?

In a nutshell

Understand the structure and functions of the gas exchange system and the effects of exercise, asthma and smoking

2

What you already know

Part 2 of 18

Before we start

What you already know

You should know that the lungs are in the chest and that we breathe in oxygen and out carbon dioxide.

3

Key words

Part 3 of 18

Key words

Words you'll need today

Alveoli
The tiny air sacs in the lungs where gases are exchanged.
Diffusion
Movement of particles from a higher to a lower concentration.
Diaphragm
The muscle below the lungs that flattens to draw air in.
Gas exchange
Oxygen passing into the blood and carbon dioxide passing out.
Ventilation
The physical movement of air in and out of the lungs - breathing.
4

Learning cycle

Part 4 of 18

Learning cycle 1 of 2

How air gets in and gases cross

A short piece of teaching, then a check to make sure it has landed.

5

Explore the idea

Part 5 of 18

Learn

Getting air in

To breathe in, the diaphragm flattens and the ribs move up and out. The chest volume increases, the pressure inside drops below the air pressure outside, and air flows in. Breathing out is largely the reverse. Nothing sucks air in - air is pushed in by the higher pressure outside.

6

Explore the idea

Part 6 of 18

Learn

The exchange surface

Air ends up in about 300 million alveoli. They give a huge surface area, walls one cell thick, a moist lining and a dense capillary network. Oxygen diffuses into the blood because blood arriving has a lower oxygen concentration; carbon dioxide diffuses the other way. Every feature of an alveolus makes diffusion faster.

7

Quick check

Part 7 of 18

Quick check

Air enters the lungs because...

8

Reset break

Part 8 of 18

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
9

Quick check

Part 9 of 18

Quick check

Which alveolus feature most increases the rate of diffusion?

10

Learning cycle

Part 10 of 18

Learning cycle 2 of 2

Exercise, asthma and smoking

A short piece of teaching, then a check to make sure it has landed.

11

Explore the idea

Part 11 of 18

Learn

Exercise

During exercise muscles respire faster, so they need more oxygen and produce more carbon dioxide. Breathing rate and depth rise, and heart rate rises to move the blood faster. Both changes maintain a steep concentration difference at the alveoli, keeping diffusion rapid.

12

Explore the idea

Part 12 of 18

Learn

Asthma and smoking

In an asthma attack the airways narrow and the lining swells and produces mucus, so less air reaches the alveoli. Smoking paralyses the cilia that clear mucus, and it destroys alveolar walls, merging many small sacs into fewer large ones. That reduces surface area permanently, which is why breathlessness from emphysema does not recover.

13

Quick check

Part 13 of 18

Quick check

During exercise, breathing gets deeper mainly to...

14

Quick check

Part 14 of 18

Quick check

Emphysema reduces gas exchange because...

15

Common mix-ups

Part 15 of 18

Common mix-ups

Things people often get wrong

  • Breathing is ventilation; respiration is a chemical reaction in cells.
  • Air is pushed in by outside pressure, not sucked in by the lungs.
  • Lungs have no muscle of their own - the diaphragm and rib muscles do the work.
  • Smoking damage to alveolar walls does not grow back.
16

Challenge round

Part 16 of 18

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

17

Mastery quiz

Part 17 of 18

Marked quiz

End of lesson quiz: Breathing, gas exchange and what damages it

6 questions, marked with the reasoning shown. No timer.

  1. 1. Gas exchange happens in the...

  2. 2. Diffusion is movement...

  3. 3. The diaphragm during inhalation...

  4. 4. An asthma attack narrows the...

  5. 5. Cilia normally...

  6. 6. Blood leaving the alveoli is...

18

Lesson round-up

Part 18 of 18

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 18 · Watch & discover

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    Understand the structure and functions of the gas exchange system and the effects of exercise, asthma and smoking

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