7. Respiration

What you need to know...
  • What is respiration?
  • What are the word equations for respiration with and without oxygen in animals, plants and fungi.
  • What type of respiration creates the most energy .
  • To be able to name two factors that are needed for the process of respiration.
What is respiration?
Respiration is a very important process carried out in every cell. In this process, a type of sugar called glucose is broken down to release energy.
Things that we need energy for include:
  • Making new cells through cell division.
  • Making substances e.g. proteins such as insulin, enzymes and more.
  • Making our muscle cells work.
  • Sending information along brain cells
  • And many many more
How much energy we get from respiration depends on whether oxygen is present or not. We breathe in oxygen and this is carried to our cells in our blood. Usually there is plenty of oxygen for all our cells. Sometimes, however there is not.
Respiration with oxygen
Animals like us get our oxygen from the air when we breathe. Plants get oxygen from the air through their leaves. When oxygen is in good supply animal cells can use this to break down glucose to water and carbon dioxide.
Lots of energy is released.
Respiration without oxygen
Sometimes our cells cannot get enough oxygen. What happens is different depending on whether the organism is an
animal, plant or fungus.
  • Animal cells: In animal cells if there is not enought oxygen, glucose cannot be fullt broken down and instead another substance called lactic acid is produced and only a small amount of energy is produced. This happens when we exercise strongly, the build up of lactic acid in our muscles is what causes our muscles to get tired and painful.

  • Plants & fungal cells: If there is not enough oxygen in plant or fungal cells, glucose is broken down to something ethanol and carbon dioxide. You might remember this from when we were studying yeast as part of the Microorganisms sub-unit.

 Other requirements for photosynthesis
Like photosynthesis, respiration is a set of complex chemical reactions and so needs enzymes to keep it all going.
Respiration is also affected by temperature and so all organisms do not cope very well with very high or low temperatures.