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SavannahYear 8
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SciencePhotosynthesis and respiration30 min★★★ difficulty

Aerobic and anaerobic respiration

Respiration happens in every living cell, every second, including in plants. It releases the energy that powers everything else a cell does - and there is a backup version for when oxygen runs short.

Part of your national curriculum
  • Biology: material cycles and energy: Understand aerobic and anaerobic respiration in living organisms, including the breakdown of organic molecules to enable all the other chemical processes necessary for life

Lesson overview

What you'll learn in this lesson

Understand aerobic and anaerobic respiration in living organisms, including the breakdown of organic molecules to enable all the other chemical processes necessary for life

Key learning points

  • • The equation and the point of it
  • • Not the same as breathing
  • • Anaerobic respiration in animals
  • • Anaerobic respiration in yeast

This lesson at a glance

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

Words to know

aerobicanaerobicrespirationlivingorganisms

Scroll down — the lesson carries on below

Part 1 of 19 · Discover5%
1

Watch & discover

Part 1 of 19

Watch first

Aerobic and anaerobic respiration

Follow how your cells use glucose and oxygen to release energy.

Do it for real

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

What happens to a leaf kept in the dark?Warming up anaerobic respiration in yeast

In a nutshell

Understand aerobic and anaerobic respiration in living organisms, including the breakdown of organic molecules to enable all the other chemical processes necessary for life

2

What you already know

Part 2 of 19

Before we start

What you already know

You should know photosynthesis makes glucose and that cells need energy.

Recap: Photosynthesis: making food from light
3

Key words

Part 3 of 19

Key words

Words you'll need today

Aerobic respiration
Releasing energy from glucose using oxygen.
Anaerobic respiration
Releasing energy from glucose without oxygen; less energy released.
Mitochondria
The organelles where most aerobic respiration happens.
Lactic acid
The product of anaerobic respiration in animal cells.
Fermentation
Anaerobic respiration in yeast, producing ethanol and carbon dioxide.
4

Learning cycle

Part 4 of 19

Learning cycle 1 of 2

Aerobic respiration

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

5

Explore the idea

Part 5 of 19

Learn

The equation and the point of it

Glucose + oxygen produces carbon dioxide + water, releasing energy. That energy is then used for movement, active transport, building large molecules, keeping warm and nerve impulses. Nothing else a cell does happens without it, which is why respiration counts as the reaction that enables all the others.

6

Explore the idea

Part 6 of 19

Learn

Not the same as breathing

Respiration is a chemical reaction inside cells, mostly in mitochondria. Breathing supplies the oxygen it needs. Cells with high energy demands, such as muscle and sperm cells, contain many more mitochondria. Plants respire too, day and night; in daylight they photosynthesise faster than they respire, which is why they release oxygen overall.

7

Quick check

Part 7 of 19

Quick check

Aerobic respiration produces...

8

Quick check

Part 8 of 19

Quick check

Most aerobic respiration occurs in the...

9

Reset break

Part 9 of 19

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
10

Learning cycle

Part 10 of 19

Learning cycle 2 of 2

When oxygen runs out

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

11

Explore the idea

Part 11 of 19

Learn

Anaerobic respiration in animals

During hard exercise, oxygen cannot arrive fast enough, so muscles switch partly to anaerobic respiration: glucose produces lactic acid, releasing much less energy per glucose molecule. Lactic acid build-up causes fatigue and a burning feeling, and afterwards you keep breathing hard to repay the oxygen debt.

12

Explore the idea

Part 12 of 19

Learn

Anaerobic respiration in yeast

Yeast respires anaerobically to produce ethanol and carbon dioxide. That is fermentation, and it makes bread rise and produces alcohol. Same principle, different products, and both are far less efficient than aerobic respiration - a useful reminder that oxygen is what makes energy release efficient.

13

Quick check

Part 13 of 19

Quick check

Anaerobic respiration in muscle produces...

14

Quick check

Part 14 of 19

Quick check

Yeast fermentation is used in baking because it produces...

15

Common mix-ups

Part 15 of 19

Common mix-ups

Things people often get wrong

  • Respiration is not breathing.
  • Plants respire as well as photosynthesise, all the time.
  • Anaerobic respiration releases less energy, not none.
  • Lactic acid does not cause muscle soreness days later - that is tissue repair.
16

Challenge round

Part 16 of 19

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

Challenge round

Part 17 of 19

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

Nothing else a cell does happens without it, which is why ____ counts as the reaction that enables all the others.

During hard exercise, oxygen cannot arrive fast enough, so muscles switch partly to ____ respiration: glucose produces lactic acid, releasing much less energy per glucose molecule.

Same principle, different products, and both are far less efficient than ____ respiration - a useful reminder that oxygen is what makes energy release efficient.

18

Mastery quiz

Part 18 of 19

Marked quiz

End of lesson quiz: Aerobic and anaerobic respiration

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

  1. 1. Respiration happens in...

  2. 2. Compared with aerobic, anaerobic respiration releases...

  3. 3. Oxygen debt is repaid by...

  4. 4. Cells needing lots of energy contain many...

  5. 5. At night a plant...

  6. 6. Energy from respiration is used for...

19

Lesson round-up

Part 19 of 19

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 19 · Watch & discover

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    Understand aerobic and anaerobic respiration in living organisms, including the breakdown of organic molecules to enable all the other chemical processes necessary for life

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