Aerobic & Anaerobic Respiration (Edexcel IGCSE Biology)
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Aerobic Respiration
Aerobic respiration requires oxygen
It is defined as the chemical reaction in cells that uses oxygen to break down nutrient molecules to release energy
Aerobic respiration is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes and reactions
Carbon dioxide and water are produced as waste products as well as releasing useful cellular energy
Word equation for aerobic respiration
Symbol equation for aerobic respiration
This equation can also be shown as a balanced chemical equation
One molecule of glucose combines with six molecules of oxygen to produce six molecules of carbon dioxide and six molecules of water
Examiner Tips and Tricks
There are usually 3 marks given for the aerobic respiration chemical equation in an exam:
One for getting the correct formula for glucose and oxygen
One for getting the correct formula for carbon dioxide and water
One for balancing the equation correctly
So make sure you can do all three to gain maximum marks!
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Anaerobic Respiration
Anaerobic respiration does not require oxygen
It is defined as the chemical reaction in cells that breaks down nutrient molecules to release energy without using oxygen
It involves the incomplete breakdown of glucose and so releases a relatively small amount of energy for use in cell processes
Different breakdown products are formed depending on the type of organism that the anaerobic respiration is taking place in
Anaerobic respiration in animals
Anaerobic respiration mainly takes place in muscle cells during vigorous exercise
When we exercise at high intensities, our muscles have a higher demand for energy
Our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration
When oxygen runs out, glucose is broken down without it, producing lactic acid instead
Glucose has not been fully broken down meaning there is still energy stored within the bonds of lactic acid molecules
Lactic acid builds up in muscle cells and lowers the pH of the muscle tissue (making the conditions more acidic)
Acidic conditions can denature the enzymes in cells
Lactic acid will eventually be broken down using oxygen to produce carbon dioxide and water as waste products
Anaerobic respiration releases less energy than aerobic respiration
Word equation for anaerobic respiration in animals
Anaerobic respiration in plants and fungi
Plants and yeast can respire without oxygen as well, breaking down glucose in the absence of oxygen to produce ethanol and carbon dioxide
Anaerobic respiration in yeast cells is called fermentation
Fermentation is economically important in the manufacture of bread (where the carbon dioxide produced helps the dough to rise) and in brewing (where the ethanol produced makes beer)
Word equation for anaerobic respiration in plants and yeast
Examiner Tips and Tricks
You need to know the word equations for anaerobic respiration in animals and plants (or fungi) but not the symbol equations
Comparing Anaerobic & Aerobic Respiration
The processes of aerobic and anaerobic respiration can be compared with regard to the need for oxygen, the products and the relative amounts of energy transferred
Comparing Aerobic & Anaerobic Respiration Table
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