lipids and proteins Flashcards
what do proteins contain
C , H , O , N
biuret test
- detects presence of protein
- blue to lilac
emulsion test
- detects presence of lipids
- add ethanol and shake
- add water
- milky, white emulsion
what are amino acids made up of?
- amine group (NH2)
- carboxylic group (COOH)
- R group (20 variations)
primary structure of protein
sequence of a chain of amino acids
secondary structure of protein
hydrogen bonds cause folding into alpha helices or beta pleated sheets
tertiary structure of protein
further folding into 3D structure due to ionic bonds, hydrogen bonds, disulphide bridges and hydrophobic interactions
quaternary structure of protein
made of more than one polypeptide chain
fibrous protein
- long strands of polypeptide chain and little to no tertiary structure
- structural properties
- insoluble
- keratin, collagen
globular protein
- polypeptide is folded and has 3D structure as result of internal bonding
- enzymes, transport, antibodies
- soluble
- unstable structure
haemoglobin
- made of 4 polypeptide chains
- contains prosthetic group (non-protein group)
R group
variable group that determines the properties of the amino acid
how does polypeptide form
- via condensation reactions
- forms peptide bonds between amino acids
what do lipids contain
C , H , O - more hydrogen than carbs
triglycerides
- 3 fatty acids
- 1 glycerol
- 3 ester bonds, via cooh of fatty acid and oh of glycerol
- hydrophobic
why aren’t lipids polymers?
not made up of monomers
properties of triglycerides
- high ratio of energy storing carbon - hydrogen bonds
- high ratio of hydrogen to oxygen atoms = metabolic water source
- insoluble in water
difference between saturated and unsaturated fatty acid
saturated = contains only single bonds between carbon atoms
unsaturated = contains double bonds between carbon atoms
phospholipids
- glycerol molecule
- phosphate group replaces one fatty acid
- 2 fatty acids
why do phospholipids form a bilayer?
- hydrophilic phosphate heads exposed to water
- hydrophobic fatty acid tails position away from water
two proteins have the same number and type of amino acids but different tertiary structure, why?
different sequences of amino acids
causing different types/ numbers of bonds
(ionic,hydrogen and disulphide)
folding of protein is different
