Water and Cells

Water is the single most abundant chemical found in living things.
Virtually all chemical reactions in life processes take place in solution in water. Some organisms can live in a dormant and desiccated state for long periods of time but require water to become active. Water is present both inside and outside cells. In the body of a mammal for example although it is about 70% water by weight, about 46% (approximately 2/3) is inside cells, and about 23% (approx. 1/3) is present outside cells in blood plasma and other body fluids.

Adding water – the WATER WEDGE – the big changer
Water molecules, assisted by enzymes, can be ‘pushed’ into certain molecules to split them into smaller sub-units.

This process is called hydrolysis (from the Greek: hydro meaning water and lysis or lusis meaning loosening or splitting). During it parts of a water molecule are added to the two separated parts. Carbohydrates, fats and proteins can be split in this way.

  • Large carbohydrates such as starch can be split to form smaller carbohydrates such as glucose.
  • Fats or lipids can be split into glycerol and other molecules including chemicals called fatty acids.
  • Proteins can be split into the buildings blocks from which they were constructed, namely amino acids.

Removing water – the ULTIMATE ‘TAKE-AWAY’
In a reverse way, enzymes can assist with the removal of water molecules enabling some small molecules to join together to form large ones. This process is called condensation and can be looked upon as condensing two or more molecules together to make one molecule.

By removing water at a molecular level:

  • simple sugars like glucose can be joined together to form complex carbohydrates such as starch,
  • glycerol and certain other molecules can form fats or lipids and
  • amino acids can be joined together to make protein.

With enzyme assistance the addition and subtraction of water molecules enables the construction and demolition of carbohydrates, fats and proteins.