(5) A comparison of aerobic respiration and anaerobic respiration in plants and animals and relative yields of ATP

In prokaryotic organisms, aerobic respiration takes place in the cytoplasm.

In eukaryotic organisms, aerobic respiration takes place in the mitochondria of cells.

Anaerobic respiration takes place in the cytoplasm plant cells, animal cells and some microorganisms.

The actual energy release powering cell chemistry takes place through a very complex biochemistry cycle involving ADP (adenosine diphosphate) and its conversion to ATP (adenosine triphosphate)

It is the ATP molecule that actually supplies the chemical energy to power most of the chemistry of any cell. The more efficient the respiration, the more ATP is made, the faster and more efficient is the chemistry of cells - see the data table for comparison of type of respiration and the relative quantities of ATP produced.

The more ATP that is made, the greater the supply of energy available.

 

Aerobic respiration in plants and animals with excess oxygen can be summarised as:

glucose  + oxygen ===>  carbon dioxide  +  water  + energy

C₆H₁₂O_6(aq)  +  6O_2(g)  ===>  6CO_2(g)  +  6H₂O_(l)  +  energy

 

Anaerobic respiration in animals, when there is a lack of oxygen

glucose  ===>  lactic acid  +  energy

C₆H₁₂O₆   ===>  2C₃H₆O₃  +  energy

 

Anaerobic respiration in organisms like plants or yeasts, when there is a lack of oxygen

glucose ===> ethanol ('alcohol')  +  carbon dioxide  +  energy

C₆H₁₂O_6(aq) ====> 2C₂H₅OH_(aq) + 2CO_2(g)  + energy

 

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Key points -  comparison of aerobic respiration and anaerobic respiration in plants and animals and relative yields of ATP

Revision notes tailored for biology students comparing aerobic and anaerobic respiration across plants, yeasts, and animals, with a focus on ATP yield:

Based on the syllabus-specifications for students taking the AQA, Edexcel and OCR GCSE level biology examinations (~US grades 9-10).
 

Types of Respiration

Type	Oxygen Required?	Organisms	Products	ATP Yield per Glucose
Aerobic	Yes	All: animals, plants, yeast	CO₂ + H₂O + lots of energy (ATP)	36–38 ATP
Anaerobic (Animals)	No	Humans & other animals	Lactic acid + little energy	2 ATP
Anaerobic (Plants & Yeast)	No	Yeast, plant cells	Ethanol + CO₂ + little energy	2 ATP

Key Differences

Aerobic Respiration

• Efficient: Produces much more ATP per glucose molecule.

• Complete breakdown of glucose into carbon dioxide and water.

• Occurs in mitochondria.

• Used most of the time when oxygen is available.

Anaerobic Respiration

• Less efficient: Only 2 ATP per glucose.

• In animals, leads to lactic acid build-up → muscle fatigue.

• In yeast/plants, produces ethanol and CO₂ (alcoholic fermentation).

• Used during oxygen-limited conditions (e.g. hard exercise or waterlogged soils).

Exam Tip:

You may be asked to:

• Compare the energy yield between aerobic and anaerobic respiration.

• Identify which organisms perform alcoholic or lactic acid fermentation.

• Write balanced chemical or word equations for both forms.

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Keywords, phrases and learning objectives for this section on respiration

Know that production of ATP molecules from respiration is important to provide energy to power most of the chemistry of cells.

Be able to compare and contrast the similarities and differences between aerobic respiration and anaerobic respiration.

Know and understand the relative different in ATP yields produced from aerobic respiration and anaerobic respiration in plants and animals.

Know that both aerobic respiration and anaerobic respiration both produce ATP and anaerobic respiration is much less efficient.

Know that aerobic and anaerobic respiration produce the different chemical products.

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