A2 Biology essay plan Watch
the title is the role of water to living organisms?
i need ideas!! as i cant really think what water does
thanks very much!!
Water is a solvent for numerous biochemical moleculesm giving solutions and enabling:
1 - Transport of nutrients, e.g. glucose and amino acids in blood, and sucrose in phloem
2 - Removal of excretory products, e.g. ammonia, urea
3 - Secreation of substances, e.g. hormones, digestive juices.
Role of water in metabolic reactions:
The majority of essential metabolic reactiosn take place in solution in water. Water is a raw material or a product of many metabolic reactions.
1 - Hydrolysis involves the addition of water (hydro) in the breakdown (lysis) of large biological molecules into their monomers/subunits, e.g. proteins into amino acids. (Water is release during condensation reactions).
2 - Water produced as a metabolic product of respiration is essential for organisms, especially those living in dry habitats.
3 - Water is needed for photosyntheis.
Role of water in supprt:
Water is not easily compressed and has an important role in support in plants and animals
1 - The uptake of water by plant cells creates a pressure against the rigid cell wall.
2 - This tugor pressure helps non-woody plants to remain upright.
3 - Water provides boyancy for aquatic organisms, e.g whales.
4 - Water has a high specific tension and water molecules have cohesive forces holding them together, due to hydrogen bonding between water molecules.
5 - These properties allow aquatic insects to walk on the surface of water, and water to be pulled through xylem in plants.
Role of water in temperature regulation:
Water has a high specific heat capacity which means it adsorbs a lot of heat energy for its temperature rise, and loses a lot to cool. This help to:
1 - Reduce temperature fluctations in organisms - especially large ones.
2 - Minimise increases in temperature in cells as a result of biochemical reactions.
3 - Reduce fluctations in temperature in aquatic habitats.
A lot of heat is needed to turn water into vapour (it has a high latent heat of vaporisation)
1 - This helps some animals to maintain a constant body temperature as a high amount of heat energy is removed from the body to evaporate sweat or during planting.
2 - In plants evaporation of water from leaves has a cooling effect.
At 4*C water is at its maximum density and becomes less dense as it freezes.
1 - Water is denser as a liquid than as a solid
2 - Thus cold water forms ice on the upper surface, insulating the aquatic organisms below.
3 - Water must lose a relatively large amount of heat energy to freeze, making the formation of ice cystals in cells less likely.
Hope my revision notes help!