Water Flashcards
Why is water of great biological importance?
It is the medium in which all metabolic reactions take place in cells.
Water is composed of which atoms?
Hydrogen and oxygen
In water, how are the atoms bonded?
Covalent bonding by sharing electrons
Is the sharing of electrons even or uneven between oxygen and hydrogen atoms?
Uneven, although water as a whole is electrically neutral
Does oxygen or hydrogen attract electrons more strongly?
Oxygen
What does oxygen attracting electrons more strong than hydrogen atoms result in?
A weak negatively charged region on the oxygen atom and a weak positively charged region on the hydrogen atoms, this also results in the asymmetrical shape
What is the separation of charge due to the electrons in the covalent bonds being unevenly shared called?
A dipole
What is the name of a molecule which has one end that is negatively charged and one end that is positively charged?
A polar molecule
Is water a polar molecule?
Yes
What bonds form between water molecules?
Hydrogen bonds
How does the polarity of water affect how hydrogen bonds form?
Hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules
Are hydrogen bonds weak or strong when there are few?
Weak
What are hydrogen bonds constantly doing because they are weak?
Breaking and reforming
What properties do water molecules have which hydrogen bonds contribute to?
- an excellent solvent
- a relatively high specific heat capacity
- a relatively high specific latent heat of vapourisation
- water is less dense when a solid
- water has high surface tension and cohesion
- it acts as a reagent
As water is a polar molecule, many ___ and ____ will dissolve in it?
Ions and covalently bonded polar substances (eg glucose)
What does the dissolving of ions and covalently bonded polar substances allow for within cells?
Chemical reactions to occur within human cells as the dissolved solutes are more chemically reactive when they are free to move about
What does water being a good solvent allow for in terms of metabolites?
They can be transported efficiently (except non polar molecules which are hydrophobic)
Why does water have a high specific heat capacity?
Due to the many hydrogen bonds present in water. It takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly
What is the advantage of water having a high SHC on living organisms?
- provides suitable habitats
- able to maintain a constant temperature as water can absorb a lot of heat without big temperature fluctuations. This is vital in maintaining temperatures that are optimal for enzyme activity.
What is water in blood plasma vital for?
Transferring heat around the body, helping to maintain a fairly constant temperature
Why does water have a high latent heat of vapourisation?
In order to change state (liquid to gas) a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate.
Why is a high LHoV an advantage for living organisms?
Only 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.
What allows for strong cohesion between water molecules?
Hydrogen bonds between water molecules
What does strong cohesions allow for in plants and animals?
Allows columns of water to move through the xylem of plants and through blood vessels in animals
