Aerobic and anaerobic respiration

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Aerobic and anaerobic respiration (KS3 Science, Biology) — use them in your lesson, or run the topic as an interactive class activity your students play as a live game.

Lesson notes

Aerobic Respiration

Requires **oxygen** to release energy from **glucose**.
Occurs in the **mitochondria** of cells.
Word equation: **glucose + oxygen → carbon dioxide + water + energy**.
Produces a **large amount of energy** efficiently.
Used during endurance activities like marathon running or long-distance swimming.

Anaerobic Respiration in Humans

Does **not require oxygen**; occurs when oxygen levels are low.
Takes place in the **cytoplasm** of cells.
Word equation: **glucose → lactic acid + energy**.
Releases **less energy** than aerobic respiration.
Used during intense exercise (e.g., sprinting, weightlifting) when oxygen supply to muscles is limited.
Build-up of **lactic acid** causes muscle fatigue and soreness.

Oxygen Debt

After intense exercise, the body must repay the **oxygen debt**.
Additional oxygen is needed to break down **lactic acid** and restore muscles.
During recovery, increased breathing and heart rate supply this oxygen.

Anaerobic Respiration in Yeast (Fermentation)

Yeast is a unicellular fungus that can perform **fermentation**.
Word equation: **glucose → ethanol + carbon dioxide + energy**.
Used in **bread making** (carbon dioxide makes dough rise) and **brewing** (ethanol is alcohol in beer/wine).

Comparison of Aerobic and Anaerobic Respiration

Aerobic requires oxygen; anaerobic does not.
Aerobic occurs in mitochondria; anaerobic occurs in cytoplasm.
Aerobic produces much more energy than anaerobic.
Aerobic products: carbon dioxide and water; anaerobic products: lactic acid (humans) or ethanol and carbon dioxide (yeast).

Aerobic respiration in a cell showing mitochondria as the site of the process.

Comparison of anaerobic respiration in human muscle cells and yeast.

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.Which of the following is the correct word equation for aerobic respiration?
Easy
- Aglucose + oxygen → carbon dioxide + water + energy
- Bglucose → lactic acid + energy
- Cglucose → ethanol + carbon dioxide + energy
- Dglucose + water → carbon dioxide + oxygen + energy
2.In which organelle does aerobic respiration occur?
Easy
- ANucleus
- BMitochondrion
- CCytoplasm
- DRibosome
3.What is the product of anaerobic respiration in humans that causes muscle fatigue?
Easy
- ACarbon dioxide
- BEthanol
- CLactic acid
- DWater
4.Which of the following is true about anaerobic respiration in yeast?
Medium
- AIt produces lactic acid and energy.
- BIt requires oxygen to occur.
- CIt produces ethanol and carbon dioxide.
- DIt occurs in the mitochondria.
5.During intense exercise, muscles use anaerobic respiration. What is the main reason for this?
Medium
- ATo produce more energy than aerobic respiration
- BBecause oxygen supply to muscles is limited
- CTo produce carbon dioxide for breathing
- DBecause glucose is not available
6.After a sprint, an athlete breathes heavily to repay an 'oxygen debt'. What is the purpose of this extra oxygen?
Hard
- ATo convert lactic acid back to glucose
- BTo break down lactic acid and restore muscles
- CTo produce more lactic acid for energy
- DTo increase the rate of anaerobic respiration
7.Which of the following statements is true?
Easy
- AAerobic respiration occurs without oxygen.
- BAnaerobic respiration produces more energy than aerobic respiration.
- CLactic acid can cause muscle fatigue and soreness.
- DOnly animal cells carry out aerobic respiration.
8.Where in the cell does anaerobic respiration occur?
Medium
- AMitochondria
- BNucleus
- CCytoplasm
- DCell membrane

More questions

9.What is the main difference between aerobic and anaerobic respiration?
Hard
- AAerobic respiration uses glucose; anaerobic does not.
- BAerobic respiration requires oxygen; anaerobic does not.
- CAerobic respiration occurs in plants; anaerobic in animals.
- DAerobic respiration produces lactic acid; anaerobic produces carbon dioxide.
10.Which of the following is a use of anaerobic respiration in yeast?
Medium
- ABread making and brewing
- BSprinting and weightlifting
- CRunning a marathon
- DPlant growth
11.A student observes that after a 100 m sprint, a runner's breathing rate remains high for several minutes. Which process explains this?
Hard
- AAerobic respiration has stopped completely.
- BThe body is repaying an oxygen debt.
- CLactic acid is being converted to glucose without oxygen.
- DAnaerobic respiration continues at the same rate.
12.Which of the following correctly compares the energy released by aerobic and anaerobic respiration?
Medium
- AAerobic releases less energy than anaerobic.
- BAerobic releases more energy than anaerobic.
- CBoth release the same amount of energy.
- DAnaerobic releases no energy.
13.What is the correct word equation for aerobic respiration?
Easy
- Aglucose + oxygen → carbon dioxide + water + energy
- Bglucose → lactic acid + energy
- Cglucose → ethanol + carbon dioxide + energy
- Dcarbon dioxide + water → glucose + oxygen
14.During anaerobic respiration in humans, which substance is produced that can cause muscle fatigue?
Easy
- Alactic acid
- Bethanol
- Ccarbon dioxide
- Doxygen
15.A student investigates respiration in yeast by mixing yeast with glucose solution in a sealed container and measuring the volume of gas produced over 30 minutes. Which gas is being produced?
Medium
- Aoxygen
- Bcarbon dioxide
- Chydrogen
- Dnitrogen
16.The table shows the energy released per gram of glucose for two types of respiration. Aerobic respiration releases 16 kJ/g, while anaerobic respiration releases 2 kJ/g. How much more energy does aerobic respiration release per gram?
Medium
- A8 kJ
- B14 kJ
- C18 kJ
- D32 kJ
17.During a 100 m sprint, an athlete's muscles use anaerobic respiration. After the race, the athlete breathes heavily for several minutes. What is the main purpose of this increased breathing?
Hard
- Ato supply oxygen to break down lactic acid
- Bto remove excess carbon dioxide from the muscles
- Cto increase the heart rate
- Dto cool down the body
18.Which of the following statements about anaerobic respiration in yeast is correct?
Medium
- AIt produces lactic acid and energy.
- BIt requires oxygen to occur.
- CIt produces ethanol and carbon dioxide.
- DIt releases more energy than aerobic respiration.
19.A baker uses yeast in bread dough. The dough rises because of gas produced during anaerobic respiration. Which gas causes the dough to rise?
Hard
- Aoxygen
- Bcarbon dioxide
- Cethanol
- Dlactic acid
20.The diagram shows a mitochondrion. Which process occurs in this organelle?
Medium
- Aanaerobic respiration
- Baerobic respiration
- Cphotosynthesis
- Dfermentation
21.A student sets up the apparatus shown to investigate respiration in yeast. Which change would indicate that respiration is occurring?
Medium
- Athe limewater turns cloudy
- Bthe yeast solution turns blue
- Cthe temperature decreases
- Dthe volume of liquid increases
22.A marathon runner uses aerobic respiration for most of the race. However, during a final sprint, the runner's muscles switch to anaerobic respiration. Which of the following best explains why this switch occurs?
Hard
- Athe muscles run out of glucose
- Bthe muscles run out of oxygen
- Cthe muscles produce too much carbon dioxide
- Dthe muscles need more water
23.A student sets up an experiment to investigate anaerobic respiration in yeast. Yeast cells are mixed with glucose solution in a sealed container with a delivery tube leading to a beaker of limewater. After 30 minutes, the limewater turns milky. Which gas produced by the yeast causes this change?
Medium
- AOxygen
- BCarbon dioxide
- CEthanol
- DNitrogen
24.In an experiment, a student measures the volume of gas produced by yeast in glucose solution at different temperatures. The results show that at 15°C, 5 cm³ of gas is produced in 10 minutes; at 25°C, 12 cm³; at 35°C, 20 cm³; and at 45°C, 8 cm³. Which statement best explains the decrease in gas production at 45°C?
Hard
- AThe yeast runs out of glucose
- BThe enzymes in yeast are denatured at high temperature
- CThe yeast switches to aerobic respiration
- DThe carbon dioxide dissolves more in warm water
25.A student investigates the effect of pH on anaerobic respiration in yeast. They add yeast to glucose solutions buffered at different pH values and measure the volume of gas produced after 20 minutes. Which of the following is a control variable in this experiment?
Medium
- AThe volume of gas produced
- BThe pH of the solution
- CThe concentration of glucose solution
- DThe temperature of the experiment
26.Which of the following is the correct word equation for anaerobic respiration in yeast?
Easy
- AGlucose → lactic acid + energy
- BGlucose + oxygen → carbon dioxide + water + energy
- CGlucose → ethanol + carbon dioxide + energy
- DGlucose → ethanol + water + energy
27.After a 100 m sprint, an athlete breathes heavily for several minutes. Which of the following best explains why this is necessary?
Medium
- ATo supply extra oxygen to break down lactic acid
- BTo remove carbon dioxide produced during the sprint
- CTo cool down the body by evaporating water
- DTo increase heart rate for recovery
28.A student uses a respirometer to measure the rate of aerobic respiration in germinating seeds. The apparatus includes a container with soda lime to absorb carbon dioxide. After 10 minutes, the coloured liquid in the capillary tube moves towards the seeds. What does this movement indicate?
Hard
- AOxygen is being produced
- BCarbon dioxide is being absorbed
- COxygen is being consumed
- DThe seeds are undergoing anaerobic respiration
29.In an experiment, a student compares the energy released by aerobic and anaerobic respiration. They burn a known mass of glucose in oxygen and measure the temperature rise in water. They also mix glucose with yeast in anaerobic conditions and measure the temperature rise. Which of the following is a valid conclusion from the experiment?
Hard
- AAerobic respiration releases less energy than anaerobic respiration
- BAnaerobic respiration releases more energy than aerobic respiration
- CAerobic respiration releases more energy than anaerobic respiration
- DBoth release the same amount of energy
30.Where does anaerobic respiration take place in a cell?
Easy
- AMitochondria
- BNucleus
- CCytoplasm
- DRibosomes
31.Which of the following is a similarity between aerobic and anaerobic respiration?
Medium
- ABoth produce carbon dioxide
- BBoth require oxygen
- CBoth release energy
- DBoth produce lactic acid
32.A baker notices that bread dough rises when left in a warm place. Which process causes the dough to rise?
Medium
- AAerobic respiration producing oxygen
- BAnaerobic respiration producing carbon dioxide
- CAerobic respiration producing carbon dioxide
- DAnaerobic respiration producing ethanol
33.A student designs an experiment to compare the rate of anaerobic respiration in yeast at two different temperatures. They use the same volume of yeast suspension and glucose solution in each setup. Which of the following would improve the validity of the experiment?
Hard
- AUse different concentrations of glucose at each temperature
- BMeasure the volume of gas produced at regular intervals
- CUse a larger volume of yeast suspension at the higher temperature
- DRepeat the experiment at each temperature and calculate the mean
34.Which of the following is a product of aerobic respiration?
Easy
- ACarbon dioxide and water
- BLactic acid and water
- CEthanol and carbon dioxide
- DOxygen and glucose
35.Which of the following is a product of anaerobic respiration in humans?
Easy
- ALactic acid
- BCarbon dioxide and water
- CEthanol
- DOxygen
36.Which of the following statements about aerobic and anaerobic respiration is correct?
Medium
- AAerobic respiration releases more energy per glucose molecule than anaerobic respiration.
- BAnaerobic respiration releases more energy per glucose molecule than aerobic respiration.
- CBoth aerobic and anaerobic respiration release the same amount of energy.
- DAnaerobic respiration does not release any energy.
37.What is the word equation for anaerobic respiration in yeast?
Medium
- AGlucose → ethanol + carbon dioxide + energy
- BGlucose → lactic acid + energy
- CGlucose + oxygen → carbon dioxide + water + energy
- DGlucose → carbon dioxide + water + energy
38.After intense exercise, an athlete breathes heavily to repay an 'oxygen debt'. What is the main purpose of this extra oxygen?
Medium
- ATo break down lactic acid produced during anaerobic respiration
- BTo produce more glucose for muscles
- CTo increase the rate of anaerobic respiration
- DTo remove carbon dioxide from the muscles
39.The table shows the energy released per gram of glucose for two types of respiration. Aerobic respiration releases 16 kJ/g, while anaerobic respiration releases 2 kJ/g. Which statement explains why anaerobic respiration releases less energy?
Hard
- AGlucose is not fully broken down in anaerobic respiration
- BAnaerobic respiration uses more oxygen
- CAnaerobic respiration produces carbon dioxide
- DAnaerobic respiration occurs in the mitochondria
40.Which of the following best describes anaerobic respiration?
Easy
- ARespiration that occurs without oxygen
- BRespiration that requires oxygen
- CRespiration that occurs only in plants
- DRespiration that produces only energy

Revision notes

## Respiration Overview Respiration provides energy for all living organisms. It occurs in every cell. Two main types: **aerobic** (with oxygen) and **anaerobic** (without oxygen). ## Aerobic Respiration - Requires **oxygen** to release energy from **glucose**. - Occurs in **mitochondria** of cells. - Equation: **glucose + oxygen → carbon dioxide + water + energy** - Efficient, produces large amount of energy. - Used during endurance activities (e.g., marathon, cycling, swimming). ## Anaerobic Respiration - Does **not** require oxygen; occurs when oxygen levels are low. - Occurs in **cytoplasm** of cells. - In humans: **glucose → lactic acid + energy** - Releases less energy than aerobic. - Used during intense exercise (e.g., sprinting, weightlifting). - **Lactic acid** buildup causes muscle fatigue and soreness. - After exercise, body repays **oxygen debt** – extra oxygen breaks down lactic acid. ### Anaerobic Respiration in Yeast (Fermentation) - Equation: **glucose → ethanol + carbon dioxide + energy** - Used in **bread making** (CO₂ makes dough rise) and **brewing** (ethanol in drinks). ## Key Differences | Feature | Aerobic | Anaerobic | |---------|---------|-----------| | Oxygen needed | Yes | No | | Location | Mitochondria | Cytoplasm | | Energy yield | High | Low | | Products (humans) | CO₂ + H₂O | Lactic acid | | Products (yeast) | – | Ethanol + CO₂ |

Aerobic respiration: Respiration that requires oxygen to release energy from glucose, occurring in mitochondria.
Anaerobic respiration: Respiration that does not require oxygen, occurring in the cytoplasm, producing lactic acid in humans or ethanol and carbon dioxide in yeast.
Mitochondria: Organelle where aerobic respiration takes place.
Cytoplasm: Cell component where anaerobic respiration occurs.
Lactic acid: Product of anaerobic respiration in humans; buildup causes muscle fatigue and soreness.
Oxygen debt: Extra oxygen needed after exercise to break down lactic acid and restore muscles.
Fermentation: Anaerobic respiration in yeast, producing ethanol and carbon dioxide.
Glucose: Sugar molecule broken down in respiration to release energy.

Flashcards

What is respiration?

Respiration provides energy for all living organisms. It occurs in every cell of every organism.

What are the two main types of respiration?

Aerobic and anaerobic respiration.

Does aerobic respiration require oxygen?

Yes, aerobic respiration requires oxygen to release energy from glucose.

Where does aerobic respiration occur in cells?

In the mitochondria.

Write the word equation for aerobic respiration.

glucose + oxygen → carbon dioxide + water + energy

What are the reactants of aerobic respiration?

Glucose and oxygen.

What are the products of aerobic respiration?

Carbon dioxide, water, and energy.

Is aerobic respiration efficient?

Yes, it is efficient and produces a large amount of energy.

Give an example of an activity that primarily uses aerobic respiration.

Running a marathon, cycling, or swimming long distances.

Does anaerobic respiration require oxygen?

No, anaerobic respiration does not require oxygen.

Where does anaerobic respiration occur in cells?

In the cytoplasm.

Write the word equation for anaerobic respiration in humans.

glucose → lactic acid + energy

How does the energy released in anaerobic respiration compare to aerobic?

Anaerobic respiration releases lower quantities of energy than aerobic respiration.

When does anaerobic respiration occur in humans?

During intense exercise when oxygen supply to muscles is limited, such as sprinting or weightlifting.

What causes muscle fatigue and soreness after intense exercise?

The buildup of lactic acid from anaerobic respiration.

What is oxygen debt?

The extra oxygen required after intense exercise to break down lactic acid and restore muscles to normal.

How does the body repay oxygen debt?

Increased breathing and heart rate supply additional oxygen to clear lactic acid and replenish energy stores.

What is fermentation?

Anaerobic respiration in yeast, a type of fungus.

Write the word equation for anaerobic respiration in yeast (fermentation).

glucose → ethanol + carbon dioxide + energy

What are two uses of fermentation?

Bread making (carbon dioxide helps dough rise) and brewing (ethanol is alcohol in drinks).

True or false: Aerobic respiration occurs without oxygen.

False.

True or false: Anaerobic respiration produces more energy than aerobic respiration.

False.

True or false: Lactic acid can cause muscle fatigue and soreness.

True.

True or false: Yeast undergo anaerobic respiration during fermentation.

True.

True or false: Only animal cells carry out aerobic respiration.

False.

Unlock all 40 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon