1.6.3 ~ water Flashcards
how much of a cell is water
75-90% of the mass of a cell
how is water involved in metabolic reactions
it is the medium where metabolic reactions take place in cells
what is water made of
-oxygen molecule
-2 hydrogen atoms
-covalent bonded
polarity of water
-water is a polar molecule
-although water as a whole is electrically neutral, the sharing of electrons between oxygen and hydrogen atoms is unequal
-the oxygen atom attracts the electrons more strongly than the negative hydrogen atoms, resulting in a weak negatively charged region on oxygen atom (δ-) and weak positively charged region on hydrogen atoms (δ+)
-this results in an asymmetrical shape
dipole in water
-separation of charge due to the electrons in covalent bonds being unevenly shared is a dipole
-water molecule has one end that is positively charged and one that is negative so it is a polar molecule
hydrogen bonding in water
-hydrogen bonds form between water molecules as a result of polarity between the positive and negative charges regions of adjacent water molecules
-hydrogen bonds are weak so are contently being broken and reforming. however, there large numbers give a strong structure
6 properties of water
-an excellent solvent
-high specific heat capacity
-high latent heat of vaporisation
-less dense when a solid
-high surface tension and cohesion
-acts a reagent
water as a solvent
-water is a polar molecule so many ions and covalently bonded polar molecules will dissolve in it
-this allows chemical reactions to occur within cells (as the dissolved solutes are more chemically reactive when they are free to move about)
-metabolites can be transported efficiently
specific heat capacity definition
The specific heat capacity of a substance is the amount of thermal energy required to raise the temperature of 1kg or (gram) of that substance by 1°C
waters specific heat capacity
4200 J/kg°C
what does a high specific heat capacity mean
a relatively large amount of energy is needed to raise its temperature
why does water have a high specific heat capacity
many hydrogen bonds, takes a lot of thermal energy to break these bonds and a lot of energy to build them, so temperature of water of water does not fluctuate greatly
advantage of high specific heat capacity of water for habitats
-buffers temperature change
-able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations
-this is important for maintaining temperatures for optimum enzyme activity
specific heat capacity of water useful for transferring heat around the body
-water is in blood plasma
-as blood passes through more active regions of the body, heat energy is absorbed but the temperature remains fairly constant
-water in tissue fluid also plays an important role maintaining a constant body temperature
why does water have a high latent heat of vaporisation
-to change sate a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
why is high latent heat of vaporisation and advantage for living organisms
-a little water is required to evaporate for the organism to lose a great amount of heat
-this provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin
why does water have strong cohesion and adhesion
hydrogen bonds between water molecules allow for strong cohesion between water molecules
what does strong cohesion of water allow for
-columns of water to move through the xylem of plants and through blood vessels in animals
-this also enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water –> allows insects such as pond skaters to float
water adhesion
-able to hydrogen bonds to other molecules such as cellulose
-also enables water to move up xylem due to transpiration
