The energy requirements of cells

All cells require a supply of chemical energy for carrying out the activities that keep them alive.

Examples of cellular activities that require energy:

  • cell division
  • synthesis of proteins from amino acids
  • active transport
  • muscle cell contraction (in animal bodies)
  • transmission of nerve impulses (in animal bodies)

The role of adenosine triphosphate (ATP)

The energy required for cellular activities is provided directly by molecules of adenosine triphosphate (ATP).

ATP is made of one adenosine molecule and three phosphate groups, called Pi for short.

ATP is made of one adenosine molecule and three phosphate groups, called Pi for short

Each molecule of ATP stores a small quantity of chemical energy. This energy can be released by breaking down ATP into adenosine diphosphate (ADP) and a phosphate group.

Chemical energy in an ATP molecule is released, leaving adenosine plus two phosphate groups.

Energy is required to regenerate molecules of ATP that have been broken down. ATP is regenerated by joining a molecule of ADP to a phosphate group.

Adding energy to adenosine plus two phosphate groups creates ATP.Adding energy to adenosine plus two phosphate groups creates ATP

The breakdown and regeneration of ATP can be summarised by the diagram below.

A flow chart.  ATP, higher energy state breaksdown creating ADP plus Pi, a lower energy state.  ADP + Pi + energy create ATP.