1.6.3 ~ water

Question 1

how much of a cell is water

Answer 1

75-90% of the mass of a cell

Question 2

how is water involved in metabolic reactions

Answer 2

it is the medium where metabolic reactions take place in cells

Question 3

what is water made of

Answer 3

-oxygen molecule
-2 hydrogen atoms
-covalent bonded

Question 4

polarity of water

Answer 4

-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

Question 5

dipole in water

Answer 5

-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

Question 6

hydrogen bonding in water

Answer 6

-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

Question 7

6 properties of water

Answer 7

-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

Question 8

water as a solvent

Answer 8

-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

Question 9

specific heat capacity definition

Answer 9

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

Question 10

waters specific heat capacity

Answer 10

4200 J/kg°C

Question 11

what does a high specific heat capacity mean

Answer 11

a relatively large amount of energy is needed to raise its temperature

Question 12

why does water have a high specific heat capacity

Answer 12

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

Question 13

advantage of high specific heat capacity of water for habitats

Answer 13

-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

Question 14

specific heat capacity of water useful for transferring heat around the body

Answer 14

-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

Question 15

why does water have a high latent heat of vaporisation

Answer 15

-to change sate a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate

Question 16

why is high latent heat of vaporisation and advantage for living organisms

Answer 16

-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

Question 17

why does water have strong cohesion and adhesion

Answer 17

hydrogen bonds between water molecules allow for strong cohesion between water molecules

Question 18

what does strong cohesion of water allow for

Answer 18

-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

Question 19

water adhesion

Answer 19

-able to hydrogen bonds to other molecules such as cellulose
-also enables water to move up xylem due to transpiration