Medium for chemical reactions: All chemical reactions take place in some kind of liquid medium.
Diffusion and Osmosis: Water is necessary for osmosis and diffusion to take place through surfaces, for example in the lungs with oxygen.
Photosynthesis: Water is extremely necessary in photosynthesis.
Water as a solvent –
Water is a good liquid to dissolve other substances into.
Transport: The blood plasma, tissue fluid and lymph is mostly made up of water. Therefore it is a good place for substances to dissolve, and then move around the body.
Removal of wastes: Water is used to carry both ammonia and urea, which are waste products from the body’s metabolism.
Secretions: Water is also used to secrete substances in the body. For example in tears, which mostly consist of water, where snake venoms have toxins which are in the suspension of water.
Water as a lubricant -
Since water is so soft, it is also commonly used in the body as a lubricant.
Mucus: Mucus is used in the body to aid movement. It is for example used in the inner gut wall, to make the “flow” easier.
Synovial fluid: Synovial fluid is used to lubricate vertebrate joints.
Pleural fluid: Pleural fluid is used to lubricate the lungs when breathing.
Pericardinal fluid: Pericardinal fluid is used to lubricate the movement in the heart.
Perivisceral fluid: This fluid is used to lubricate the movement of internal organs, for example the motion of the alimentary canal.
Supporting role of water –
As water has a large cohesive force, which means that the molecules stick together, water is hard to compress and therefore used to support structures.
Hydrostatic skeleton: Water is used to support the medium within animals, for example the earthworm.
Turgor pressure: Many plants are supported by the osmotic influx of water into their cells.
Humours of the eye: Water is used to maintain the round shape of the eyes in vertebrates.
Amniotic fluid: Amniotic fluid is used to support and protect the fetus of mammals during its development.
Erection of the penis: Erection of the male penis takes place as blood, a substance that mainly consists of water, ‘fills’ the organ.
Medium in which to live: Since water provides such good support, and it is easy to move in, it is used as a habitat by large organisms which would not be able to live above the see, for example the whale.
Other functions of water:
Temperature control: Evaporation of water is extremely important as it is used to cool down the body, for example when sweating.
Hearing and balance: Water also plays a big role in the endolymph and perilymph which helps us keeping our balance and hearing.
