2.1.2 biological molcules Flashcards
why is a water molecule polar
the oxygen atom is more electronegative so it draws the shared pair of electrons towards it. this gives it a δ- charge and therefore leaving the hydrogen atoms with δ+ charges.
how can water form hydrogen bonds
the δ- charge attracts the δ+ charge forming hydrogen bonds.
why does water have a high specific heat capacity
the specific heat capacity is the energy needed to raise the temperature of 1 mole of a substance by 1 degree.
the hydrogen bond absorb a lot of heat energy so it requires lots of energy to heat up.
why does water have a high latent heat of evaporation
it takes a lot of heat to break the hydrogen bonds, so lots of energy is used up evaporating water
what is an advantage of waters high specific heat capacity
it means the temperature stays stable making it a good habitat.
what is an advantage of waters high latent heat of evaporation
it can be used as a coolant e.g. in sweat it uses heat energy from the animal to evaporate cooling the surface of the skin
why is water adhesive and cohesive
the polar bonds attract other water molecules so they are cohesive. the polar bonds also attract other polar molecules.
what is an advantage of waters adhesion and cohesion
it helps transport substances as water can flow like in a transpiration stream
why is water a good solvent
the δ- charge is attracted to positive ions and the δ+ charge is attracted to the negative ions in ionic compounds. the water molecules surround the ions dissolving them
why is water being a good solvent helpful
we can transport ions in our blood
why is water less dense when it is solid (ice)
the hydrogen bonds fix the water molecules in a lattice. as the molecules are held further apart from each other ice is less dense.
why is it helpful to living organisms that ice is less dense than water
the ice will float on top of water so it forms an insulating layer. this stops water under freezing so that aquatic animals can survive in cold conditions.
what is a polymer
a polymer is a long chain molecule made up of subunits called monomers.
what are the monomers that make up polysaccharides
monosaccharides
what is the difference between alpha and beta glucose
the group on carbon 1 is reversed
name a pentose sugar
ribose, deoxyribose
what 3 elements are carbohydrates made up of
carbon, hydrogen and oxygen
what bonds join monosaccharides
glycosidic bonds
what kind of reaction is the joining of monosaccharides
condensation reaction
what is a condensation reaction
when two molecules are joined together and a small molecule (often water) is lost
what is a hydrolysis reaction
a process of breaking down a chemical compound by adding water that involves splitting a bond
what is a disaccharide
two monosaccharides bonded together by a glycosidic bond
what disaccharide is formed when two molecules of alpha glucose are joined
maltose
what disaccharide is formed when alpha glucose and fructose are joined
sucrose
what disaccharide is formed when glucose and galactose are joined
lactose
what is the function of starch
it stores excess glucose in plants
it is compact due to its coiled and sometimes branched structure
it is insoluble so does not cause water to enter cells via osmosis
what is the structure of the starch amylose
it is a long unbranched chain of alpha glycose.
it only contains 1,4 glycosidic bonds which make it form a coiled shape
what is the structure of the starch amylopectin
a long branched chain of alpha glucose. it contains both 1,4 and 1,6 glycosidic bonds
its branches allow glucose to be releases quickly as enzymes can work at multiple sites.
what is the function of glycogen
it stores excess glucose in animals
what is the structure of glycogen
it is a long branched chain of alpha glucose (more branched than amylopectin)
why do animals use glycogen and not amylopectin
they have higher metabolic rates so they need to break down stores of glucose quicker so that it can be used in respiration.
what is the function of cellulose
it is found in plant cell walls and provides structural support to plants
what is the structure of cellulose
it is a long unbranched chain of beta glucose. alternate beta glucose molecules are flipped so that glycosidic bonds can form
these chains are linked by hydrogen bond to make fibres called microfibrils
what is the structure of a triglyceride
it contains on glycerol joined by ester bonds to three fatty acids. the tails are hydrophobic so it makes triglycerides insoluble in water.
what makes a fatty acid unsaturated
double bonds in the carbon chain, this causes the chain to kink
what is the structure of a phospholipid
the glycerol is ester bonded to 2 fatty acids and a phosphate group. the phosphate group is hydrophilic and the fatty acids are hydrophobic
how does the structure of triglycerides help its function
triglycerides are used as energy storage molecules in plants and animals.
the long hydrocarbon chains in the fatty acids store lots of chemical energy that is released when broken down.
they are insoluble so it doesn’t cause water to enter cell and make it burst.
they bundle together into insoluble droplets with fatty acids facing in
how does the structure of phospholipids help its function
phospholipids form phospholipid bilayers which form cell membranes. the fatty acid are on the inside of the bilayer and the phosphate heads face out.
the centre of the bilayer is hydrophobic so water soluble substances cant diffuse through
how does the structure of cholesterol help its function
cholesterol has a hydrocarbon ring with a polar OH group attached to a hydrocarbon tail. it helps regulate fluidity in a membrane.
it has a small flattened shape so it can fit between phospholipids
at high temperatures it binds to the fatty acids and pulls them closer decreasing fluidity
at low temperatures it increases fluidity by stopping fatty acids packing too closely together.
what is a polypeptide
a polymer made up of amino acid monomers
what is a dipeptide
two amino acids joined together
what is the general structure of an amino acid
H2NCH(R)COOH
(amine group, variable group, carboxyl group)
which amino acid has just a H for its variable group
glycine
what bonds join together amino acids
peptide bond. the amine and carboxyl group join together and lose a molecule of water
what does a peptide bond look like
O H
|| |
C ___ N
what is the primary structure of a protein
the sequence of amino acids in a polypeptide chain
what bonds are found in the primary structure
peptide bonds holding together amino acids
what is the secondary structure of a protein
the alpha helix and beta pleated sheets formed by hydrogen bonds between nearby amino acids
what bonds are found in the secondary structure
hydrogen bonds
what is the tertiary structure of a protein
the coiled/folded chain is coiled and folded further. forms the final 3D structure of a polypeptide chain
what bonds are found in the tertiary structure
ionic bonds - attractions between positively charged R groups and negatively charged R groups
disulfide bonds - cysteine has sulfur in its R group. when 2 cysteines are near a disulfide bridge forms
Hydrophobic and Hydrophilic interactions - hydrophobic groups tend to clump together pushing hydrophilic groups to the outside
hydrogen bonds - δ+ hydrogens bond with δ- atoms
what is the quaternary structure of a protein
how multiple polypeptide chains are assembled together in a protein. it is the proteins final 3D structure
what bonds are found in the quaternary structure
ionic bonds - attractions between positively charged R groups and negatively charged R groups
disulfide bonds - cysteine has sulfur in its R group. when 2 cysteines are near a disulfide bridge forms
Hydrophobic and Hydrophilic interactions - hydrophobic groups tend to clump together pushing hydrophilic groups to the outside
hydrogen bonds - δ+ hydrogens bond with δ- atoms
what is a globular protein
the hydrophilic R groups on the amino acids are pushed to the outside, in the tertiary structure. this makes them soluble so they can be transported.
function of haemoglobin
haemoglobin carries oxygen around the body in red blood cells.
what is the structure of haemoglobin
It is known as a conjugated protein, so it has a non-protein prosthetic group attached. it has 4 polypeptide chains each has a haem group. the haem group id the prosthetic group that contains iron.
function of insulin
it is a hormone secreted from the pancreas. it helps to regulate blood glucose levels. it is very soluble so it can be transported in the blood
what is the structure of insulin
2 polypeptide chains held together by disulfide bonds
function of amylase
it is an enzyme that catalyses the breakdown of starch in the digestive system.
what is the structure of amylase
it is a single polypeptide chain that contains both alpha helixes and beta pleated sheets.
what is a fibrous protein
thy are insoluble and strong. they are structural proteins that are fairly unreactive
what is collagen
it is found in animal connective tissue. it is a very strong molecule. minerals bind to the protein to increase its rigidity
what is keratin
found in many of the external structures of animals such as skin hair and nails. it can be flexible or hard and tough.
what is elastin
found in elastic connective tissue. its is elastic and allows tissues to turn to their original shape after they have been stretched.
what is the reagent we use to test for sugars
benedict’s
how do we test for reducing sugars
add benedict’s to a sample and heat in a water bath
if a reducing sugar is present then a coloured precipitate will form. the higher the concentration of sugar the further the colour change goes.
blue to red, yellow or green
how go we test for non-reducing sugars
we have to break the sugars down into monosaccharides by adding dilute HCl and heating in a water bath. them wee neutralise with sodium hydrogen carbonate.
then we carry out the benedict’s test how you would for a reducing sugar.
how do we test for starch
add iodine solution if starch is present it will change from orange/brown to blue/black
how do we test for proteins
add a few drops of NaOH to make test solution alkaline
the add copper (II) sulfate solution (biuret test)
if protein is present colour change from blue to purple
how do we test for lipids
we use the emulsion test
shake sample with ethanol for a minute and then pour into water
if lipid is present the solution turns milky
what is colorimetry
colorimetry is a technique used to find the concentration of a solution based on the intensity of light (of a specific wavelength) it absorbs or scatters.
The amount of light that passes through a sample is detected, giving an indication as to the amount of light absorbed by the sample.
A calibration curve is made using the absorbances of solutions of known concentrations.
The absorbance of the unknown concentration is compared to the calibration curve, and the concentration is found.
what id a biosensor
Biosensors are analytical devices that convert a biological response into an electrical signal.
what is chromatography
use a chromatography plate covered in a thin layer of silica gel. draw a pencil line near bottom and a spot of unknown. place in a beaker of solvent. product separate out. draw a pencil line where solvent ends up.
substances separate as they have different solubilities and attraction to the stationary phase.
how do we calculate the rf value
rf = distance moved by spot/distance moved by solvent
