Biological Molecules - Water Flashcards
What is the structure of water?
It is composed of atoms of hydrogen and oxygen.
One atom of oxygen combines with two atoms of hydrogen by sharing electrons (covalent bonding)
Why is water a polar molecule?
The sharing of the electrons is uneven between the oxygen and hydrogen atoms
The oxygen atom attracts the electrons more strongly than the hydrogen atoms, resulting in a weak negatively charged region on the oxygen atom (δ-) and a weak positively charged region on the hydrogen atoms(δ+), this also results in the asymmetrical shape
What bonds form between water molecules?
Hydrogen bonds
Why do hydrogen bonds form between water molecules?
As a result of the polarity of water hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules
What happens when there are a large number of hydrogen bonds?
They form a strong structure
What properties allow water to play an essential role in living organisms?
The polarity of water molecules
The presence and number of hydrogen bonds between water molecules
What are the important properties of water?
An excellent solvent
A metabolite in many metabolic reactions, including condensation and hydrolysis reactions
A relatively high specific heat capacity
A relatively high latent heat of vaporisation
Has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air
What is water a metabolite in?
In metabolic reactions such as condensation and hydrolysis which are used in forming and breaking of chemical bonds.
Why is water an excellent solvent?
As it is polar molecule many ions and covalently bonded polar substances 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 (except non-polar molecules which are hydrophobic)
Metabolic reactions can occur within it §
What is a specific heat capacity?
The energy required to raise the temperature of 1 kg of a substance by 1C
Water has a high specific heat capacity of 4200 J / Kg C meaning a relatively large amount of energy is required to raise its temperature
Why does water have a relatively high specific heat capacity?
It is 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 relatively high specific heat capacity?
Provides suitable habitats
Is able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations
This is vital in maintaining temperatures that are optimal for enzyme activity
Buffering changes in temperature
Why does water have a relatively high latent heat of vaporisation?
As water has many hydrogen bonds
A large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
What are the advantages of a relatively high latent heat of vaporisation?
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 organism
For example, the transpiration from leaves or evaporation of water in sweat on the skin
Why is there strong cohesion between water molecules?
Due to the many hydrogen bonds between water molecules
