Energy and ATP

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Energy and ATP

  • All living organisms require energy in order to remain alive; this initially comes fro the sun.
  • Plants use solar energy to combine water and carbon dioxide into complex organic molecules, by the process of photosynthesis.
  • Plants and animals break down these organic molecules to make ATP, which is used as an energy source to carry out processes that are essential to life.

What is energy?

Energy is defined as 'the ability to do work'. Here are some facts about energy:

  • It takes a variety of different forms, e.g. light, heat, sound, electrical, magnetic, chemical and atomic energy.
  • It can be changed from one form into another.
  • It cannot be created or destroyed.
  • It is measured in joules.

Why do organisms need energy?

  • Without some input of energy natural processes tend to break down in disorder, which is a condition which would lead to their death.
  • Energy is needed for:
  • Metabolism - all reactions that take place in living organisms involve energy.
  • Movement - bother within an organism, e.g. circulation of blood, and of the organism, e.g. locomotion.
  • Active transport of ions and molecules against a concentration gradient across plasma membrane.
  • Maintainance, repair, division of cells and of organelles within the cells.
  • Production of substances used within organisms, for example, enzymes and hormones.
  • Maintenance of body temperature in birds and mammals. These organisms are endothermic and need energy to replace that lost as heat to the environment.

Energy and Metabolism:

The flow of energy through living systmes occurs in three stages:

  • Light energy from the sun is converted by plants into chemical energy during photosynthesis.
  • The chemical energy of photosynthesis, in the form of organic molecules, is converted into ATP during respiration in all cells.
  • ATP is used by cells to perform useful work.

How ATP stores energy:

  • ATP has three phosphate groups and they are the key to how ATP stores energy.
  • The bonds between the phosphate groups are unstable and so have a low activation energy and so are easily broken.
  • When they


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