Aerobic and anaerobic respiration
Respiration happens in every living cell, every second. It is the reaction that makes energy available for movement, growth, warmth and every other chemical process of life.
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
- • Aerobic respiration
- • Anaerobic respiration in animals
- • Anaerobic respiration in yeast
- • Comparing the two
This lesson at a glance
- 28 minutes
- 27 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 27
Visual introductionPicture this
Aerobic and anaerobic respiration
Respiration happens in every living cell, every second. It is the reaction that makes energy available for movement, growth, warmth and every other chemical process of life.
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
What you already know
Part 2 of 27
Before we start
What you already know
You should already know that cells release energy from glucose, and that oxygen reaches cells through the blood.
Key words
Part 3 of 27
Key words
Words you'll need today
- Aerobic respiration
- Releasing energy from glucose using oxygen.
- Anaerobic respiration
- Releasing energy from glucose without oxygen.
- Lactic acid
- The waste made when muscles respire without enough oxygen.
- Fermentation
- Anaerobic respiration in yeast, making ethanol and carbon dioxide.
- Oxygen debt
- The extra oxygen needed afterwards to clear lactic acid.
Reset break
Part 4 of 27
Pause
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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.
Learning cycle
Part 5 of 27
Learning cycle 1 of 2
With oxygen
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 6 of 27
Learn
Aerobic respiration
Glucose + oxygen → carbon dioxide + water. This exothermic reaction occurs mainly in the mitochondria and transfers energy for muscle contraction, keeping warm, building larger molecules and active transport. Cells with high energy demands, such as muscle cells, contain many mitochondria.
Explore the idea
Part 7 of 27
Learn
Anaerobic respiration in animals
When oxygen cannot be supplied fast enough, muscle cells break glucose down to lactic acid. This releases far less energy per glucose molecule because the glucose is only partly broken down, but it releases it quickly. Lactic acid build-up causes muscle fatigue and creates an oxygen debt to be repaid afterwards.
Reset break
Part 8 of 27
Pause
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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.
Quick check
Part 9 of 27
Quick check
Part 10 of 27
Learning cycle
Part 11 of 27
Learning cycle 2 of 2
Without oxygen, and comparing
A short piece of teaching, then a check to make sure it has landed.
Reset break
Part 12 of 27
Pause
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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.
Explore the idea
Part 13 of 27
Learn
Anaerobic respiration in yeast
In yeast, anaerobic respiration produces ethanol and carbon dioxide, a process called fermentation and used in brewing and bread-making. The carbon dioxide makes dough rise; the ethanol evaporates during baking.
Explore the idea
Part 14 of 27
Learn
Comparing the two
Both start with glucose and release energy. Aerobic respiration needs oxygen, releases much more energy and produces carbon dioxide and water. Anaerobic respiration needs no oxygen, releases less energy and leaves a partly broken-down product that must be dealt with later.
Quick check
Part 15 of 27
Reset break
Part 16 of 27
Pause
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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.
Quick check
Part 17 of 27
Explore the idea
Part 18 of 27
Worked example
Worked answer: explain why a sprinter continues to breathe heavily after finishing (3 marks)
During the sprint the muscles respired anaerobically because oxygen could not be delivered fast enough, producing lactic acid (1). Extra oxygen is needed afterwards to break this lactic acid down, which is the oxygen debt (1), so deep, rapid breathing continues until the debt is repaid and lactic acid levels return to normal (1).
Common mix-ups
Part 19 of 27
Common mix-ups
Things people often get wrong
- People often think respiration means breathing. Respiration is a reaction inside cells that happens even when you hold your breath.
- People often think anaerobic respiration releases more energy. It releases far less per glucose molecule, but it releases it quickly.
Reset break
Part 20 of 27
Pause
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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.
Challenge round
Part 21 of 27
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
Challenge round
Part 22 of 27
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
In yeast, ____ respiration produces ethanol and carbon dioxide, a process called fermentation and used in brewing and bread-making.
____ respiration needs oxygen, releases much more energy and produces carbon dioxide and water.
Anaerobic ____ needs no oxygen, releases less energy and leaves a partly broken-down product that must be dealt with later.
Challenge round
Part 23 of 27
Game · Recall cards
What are the products of aerobic respiration?
Card 1 of 4
Reset break
Part 24 of 27
Pause
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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.
Exit quiz
Part 25 of 27
Exit quiz
Show what you've learned
6 questions, marked together at the end. Nothing is timed.
1. Aerobic respiration produces...
2. Anaerobic respiration in muscle produces...
3. Yeast respiring without oxygen makes ethanol and...
4. Compared with aerobic respiration, anaerobic respiration releases...
5. Oxygen debt is repaid by...
6. Respiration happens in...
Mastery quiz
Part 26 of 27
Marked quiz
End of lesson quiz: Aerobic and anaerobic respiration
4 questions, marked with the reasoning shown. No timer.
1. What are the products of aerobic respiration?
2. Why does anaerobic respiration release less energy than aerobic?
3. What causes muscle fatigue during intense exercise?
4. Aerobic respiration produces
Lesson round-up
Part 27 of 27
Lesson round-up
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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