Water The molecule consists of one oxygen atom covalently bonded to two hydrogen atoms. the oxygen atom is capable of pulling them towards itself and further away from the hydrogen atoms. the oxygen part becomes slightly negatively charged, and the hydrogen atoms slightly positively charged. it forms hydrogen bonds Properties of water molecules The solvent properties of water To dissolve chemicals inside the cells/ metabolic reaction takes place in aqeous solutions Uptake of mineral salts from soil Excretion of waste products dissolved in water e.g urine Water has high solvent of polar molecules e.g. ionic compounds like NaCl On contact with water the ions and the polar group are surrounded by water molecules which separate the molecules from each other. Biochemical reaction takes place in aqueous conditions. Water as a solvent acts as transport medium e.g. in blood High heat capacity Water has high heat capacity A large amount of heat energy results in a small rise in temperature. Temperature changes within water or aqueous unitary therefore minimized. Biochemical processes consequently operate over a small temperature range and are less likely to be affected extremities of temperatures. Water also provides a very constant external environment for many cell and organisms. High heat of evaporation Latent of evaporation is the measure of vaporization is a measure of heat energy required to vaporize a liquid. A large amount of water is required to make water vapour. This is due to hydrogen bonding of water molecules. Therefore water have usually high boiling point. Evaporating water as a result takes a lot of heat energy with them from the surrounding thus cooling takes place. This is made use of in the transpiration, sweating and panting of mammals. High heat of evaporation also means that a large amount of heat can be lost with minimal loss the body, plant etc High heat of fusion Latent heat of fusion is the measure of the heat energy required to melt a solid i.e. (ice) Ice requires a relative large amount of heat energy to thaw it. Conversely, liquid must loss a relative large amount of heat to freeze. Content of a cell and their environment are less likely to freeze. Density and freezing properties Water has highest density at 4 degrees Its density increases as the temperature decreases Ice therefore tends to float. Ice insulates the water below it thus increasing survival chance of organisms below it. Since water below 4 degrees tend to rise, this also tends to maintain circulation in lentx ecosystem. This may result in nutrient cycling and colonization of water to greater depth. Ice therefore tends to float. Ice insulates the water below it thus increasing survival chance of organisms below it. Since water below 4 degrees tend to rise, this also tends to maintain circulation in lentx ecosystem. This may result in nutrient cycling and colonization of water to greater depth. High surface tension and cohesion Cohesion is the force where individual molecules stick together at the surface, a force called surface tension between the molecules as they try to occupy the least possible space (ideally a sphere). Water has a higher surface tension which makes it possible for small organism to skate over its surface. The high cohesion of water is important in cell and in the translocation of water in the xylem vessel. Movement of water in the xylem Habitat for less dense aquatic organism Water as a reagent Water is biological significant as an essential metabolite that is , it takes part in chemical reaction of metabolism . For example it is used as a source of hydrogen and electron. Functions of water Turgidity of exoskeletons Preventing friction of joints /lubricant Fertilization of swimming gametes Component of blood Raw material for photosynthesis Part of fluid produced e.g. mucus and tears to clean the body Property importance role in living organisms solvent Allows cells to maintain concentration gradients Any polar molecule will dissolve in water 70-95% of cytoplasm is water cohesion Water molecules stick to each other, creating surface tension Transport of water in xylem relies in cohesion of water habitat Water is a common habitat Water contains oxygen that is essential to life Fish and marine creatures metabolic Water is a reactant in important chemical processes Used in hydrolysis and photosynthesis freezing ice is less dense than water and foats organism to survive the water beneath