4.4.2.1a - Aerobic and Anaerobic Respiration
Respiration is a chemical process happening inside living cells, not the same thing as breathing. It transfers energy from glucose so cells can carry out life processes. This lesson compares aerobic and anaerobic respiration at AQA depth: oxygen use, word equations, products and the relative amount of energy transferred.
Cellular respiration and energy
Cellular respiration is an exothermic reaction that happens continuously in living cells. Exothermic means energy is transferred to the surroundings. In Biology answers, it is better to say energy is transferred by respiration, not that energy is made or produced.
Cellular respiration
Cellular respiration is an exothermic reaction that continuously occurs in living cells and transfers energy from glucose for living processes.
The energy transferred by respiration supplies the energy needed for living processes. AQA names three examples:
| Living process | How the transferred energy is used |
|---|---|
| Chemical reactions to build larger molecules | Smaller molecules are joined to make larger biological molecules. |
| Movement | Muscles contract in animals, and cell contents can move inside cells. |
| Keeping warm | Mammals and birds use energy transferred by respiration to help maintain body temperature. |
Respiration happens in plants, animals and microorganisms. Plants photosynthesise in the light, but their cells still respire continuously because living cells need energy all the time.
Aerobic respiration equation
Aerobic means using oxygen. In aerobic respiration, glucose reacts with oxygen and the products are carbon dioxide and water.
Aerobic respiration word equation
AQA expects you to recognise these chemical symbols:
| Substance | Chemical symbol |
|---|---|
| glucose | C6H12O6 |
| oxygen | O2 |
| carbon dioxide | CO2 |
| water | H2O |
You do not need to turn this lesson into a Chemistry balancing exercise. The Biology point is that aerobic respiration uses glucose and oxygen, produces carbon dioxide and water, and transfers energy for living processes.
Anaerobic respiration equations
Anaerobic means without oxygen. Anaerobic respiration still transfers energy from glucose, but oxygen is not used. Because glucose is only partly broken down, AQA describes this as incomplete oxidation of glucose.
In muscle cells, anaerobic respiration is represented by:
Anaerobic respiration in muscles
In plant and yeast cells, anaerobic respiration is represented by:
Anaerobic respiration in plant and yeast cells
This lesson uses these equations only to compare products and energy transfer. The next respiration lesson deals with the detailed muscle and fermentation contexts.
Continue this lesson.
You’re previewing NovaLearn without an account. Create a free account to read the rest.
Create free account