substances dissolve in water - minerals, gases, some vitamins
carries
transport medium - transports substances around the body or plant , e.g. mineral salts are carried in water in plants, in humans blood is 50% water, which is transport medium
chemical reaction
during digestion of organic molecules, photosynthesis
lubricant
mucus uses water as a dissolving mechanism
excretion
waste metabolic substances are dissolved in water
gaseous exchange
in the lungs for diffusion and in the stoma
reproduction
all mammals and some plants need water for reproduction and in pregnancy the embryo is protected by amniotic fluid (mainly water)
support
cytoplasm is made mainly of water, fluid in the eye maintains its shape, plant cell vacuoles contain cell sap to maintain turgidity
temperature control
plants and animals use water to keep their bodies cool - sweating and transpiration
