ZIMSEC O Level Biology Notes:Properties and Biological significance of water

Property: High surface tension and cohesion (adhesion and cohesion)

  • Cohesion is the force whereby individual molecules stick together.
  • Adhesion is the force whereby water molecules stick to other surfaces.

Biological role

  • Cohesion helps water to move as an unbroken column in the xylem tubes in plants.
  • Adhesion helps the water to stick to the inside of the vascular bundle.
  • High surface tension resulting from high cohesion forces enable small organisms such as insects to skate the surface of the water.

Property: Water as a reagent

  • Water is biologically significant as an essential metabolite, that is, it participates in the chemical reactions of metabolism.
  • For example water is used as a source of hydrogen in photosynthesis and in hydrolysis reactions, condensation and respiration.

To access more topics go to the O Level Biology Notes page