2.2 - Biological Molecules Flashcards
What is a condensation reaction?
Reaction that occurs when two molecules are joined together with the removal of water
Hydrogen bond def
A weak interaction that can occur whenever molecules contain a slightly negatively charged atom bonded to a slightly positive charged hydrogen atom.
Hydrolysis reaction def
Reaction that occurs when a molecule is split into two smaller molecules with the addition of water
Monomer def
A small molecule which binds to many other identical molecules to form a polymer
Polymer def
A large molecule made from many smaller molecules called monomers
Name of two monomers joined together
“Di” - mer, dimer
What are condensation and hydrolysis reactions responsible for?
Condensation - linking of monomers with removal of water
Hydrolysis - splitting apart monomers with production of water
Monomer and polymer for a carbohydrate
Monomer - monosaccharide
Polymer- polysaccharide
Monomer and polymer for proteins
Monomer - amino acids
Polymer - Polypeptides and proteins
Monomer and polymer for Nucleic acids
Monomer - nucleotides
Polymer - DNA and RNA
What is a polar molecule?
Where a molecule has an uneven distribution of charge.
One side of the molecule is slightly negative, while the other side is slightly positive.
What is a hydrogen bond?
How strong/weak is it?
A weak interaction which occurs wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom.
The bond is weaker than a covalent bond.
What is a covalent bond?
A covalent bond is the electrostatic attraction between a shared pair of electrons and the atom’s nuclei
Properties of water
Liquid at room temperature Ice is less dense than liquid water It is a good solvent Cohesion and surface tension High specific heat capacity High latent heat of vaporisation It is a metabolite(reactant in metabolic processes or reactions)
Why is water a liquid at room temperature?
There are many hydrogen bonds between water molecules.
This makes it more difficult for them to escape to become a gas
It also has quite a low viscosity, so can flow easier.
Uses of water being a liquid at room temperature.
- It can provide habitats for living organisms in rivers, lakes and seas.
- forms a major component of the tissues in living organisms
- provide a reaction medium for chemical reaction/acts as a metabolite
- provide an effective transport medium, e.g. in blood and xylem vessels
Why is ice less dense than water?
At freezing point, because of its polar nature, the water molecules align themselves in a structure which is less dense than liquid water.
Uses of ice being less dense than water
- Aquatic organisms have a stable environment in which to live in through the winter
- Ponds and other bodies of water are insulated against extreme cold, due to the layer of ice on top of the water reducing the heat loss from the rest of the pond/water body.
Why is water a good solvent?
Is a good solvent for ionic solutes
As water is polar
So positive and negative parts of the water molecule are attracted to the negative and positive parts of the solute.
The water molecules will cluster around these charged parts of the solute molecule or ions, and will help to separate them and keep them apart.
They will dissolve at this point as a solution is formed.
Benefits of water being a good solvent
- Molecules and ions can move around and react together in water. Many of these reaction happen in the cytoplasm of the cell, which is over 70% water.
- molecules and ions can be transported around living things whilst diddolved in water.
What gives water cohesion?
Cohesion - Hydrogen bonds between water molecules pull them together.
What gives water surface tension?
Water molecules at surface are all hydrogen-bonded to the mole.cues beneath them.
This means that they are more attracted to the water molecules beneath than to the air molecules above.
This means the surface of the water contracts(as molecules are being pulled inwards), and it gives the surface of the water an ability to resist force applied to it
Benefits of cohesion and surface tension:
- Columns of water in plant vascular tissue are pulled up the the xylem tissue together from the roots due to cohesion.
- insects like pond-skaters can walk on water due to surface tension of water bodies.
What is specific heat capacity?
Amount of heat required to raise the temperature of 1 gram of substance by 1 degree Celsius
Why does water have high specific heat capacity?
Water molecules are held together quite tightly by hydrogen bonds.
Therefore you have to put a lot of heat energy to increase their KE and temperature.
Benefits of water having high specific heat capacity:
- Living things, including prokaryotes and eukaryotes, need a stable temperature for enzyme-controlled reactions to happen properly
Aquatic organisms need a stable environment in which to live
What is latent heat of vaporisation?
The amount of energy required to transform a liquid substance into a gas or vapour.
Why water has high latent heat of vaporisation
- The water molecules are held together by many hydrogen bonds, a large amount of energy is needed for water molecules to evaporate.
Benefits of high latent heat of vaporisation of water:
- Water can therefore help to cool living organism and keep their temperature stable.
E.g. mammals are cooled when sweat evaporates, or plants are cooled when water evaporates from mesophyll cells(transpiration)
Benefits of water in reactions
- hydrolysis reactions - helps break apart polymers, like digestion of starch, proteins and lipids
- reactant in photosynthesis to produce ATP and transfer energy to plant.
- condensation reactions - used to synthesise large biological molecules
Def of carbohydrates
A group of molecules containing Carbon, Hydrogen and Oxygen
Def of glycosidic bond
A bond formed between two monosaccharides by a hydrolysis reaction.
Uses of carbohydrates
- Source of energy(e.g. glucose)
- A store of energy(e.g starch in plants and glycogen in animals)
- structural units(e.g. cellulose in plants and chitin in insects).
- Can be part of other molecules, like nucleic acids and glycolipids
What are the three main groups of carbohydrates?
- Monosaccharides
- Disaccharides
- Polysaccharides
Importance of monosaccharides
- act as a source of energy
- well suited to this role as they contain large numbers of carbon-hydrogen bonds
- they are soluble in water, and insoluble in non-polar solvents.
