amino acids, proteins and DNA Flashcards
what makes up an amino acid
amine group - NH2
carboxyl group - COOH
each group is attached to a central carbon with a H and a variable group depending on which amino acid.
what is a zwitterion
molecules which contain both positive and negative charges within the same structure
how does a zwitterion form
amine group protonation - NH2 gains a proton and becomes positively charged - NH3
carboxyl group deprotonation - COOH loses a proton and becomes negatively charged - COO-
how does the zwitterion formed change depending on pH
acidic - COOH is deprotonated
neutral - both groups are ionised
alkaline - NH2 is protonated
describe the optical activity of amino acids
all amino acids except glycine can form enantiomers as there will be a chiral carbon
how is a protein formed
a chain of amino acids are created through condensation reactions, forming peptide bonds, removing a molecule of water. the peptide bond forms between the amine group of 1 amino acid and the carboxyl group of another amino acid
describe the structure of proteins
primary - the sequence of amino acids in the polypeptide chain
secondary - coiling into a helices or folding into b pleated sheets. hydrogen bonding will form.
tertiary - overall 3D shape of the protein due to folding and coiling. further ionic/covalent bonding and disulphide bridges
how are proteins denatured
at high temps or changes in pH. the bonding in the tertiary structure will break, changing the proteins shape
in what reactions are proteins made and broken
made via condensation, forming a peptide bond, removing a water molecule
broken via hydrolysis, breaking a peptide bond, with the addition of water
why is thin layer chromatography used
used to separate and identify amino acids in a mixture
how do you calculate Rf
distanced moved by amino acid/ distance moved by solvent
what are enzymes
proteins that speed up rate of reaction by reducing the activation energy
how do enzymes work
substrates will bind to the enzymes forming an enzyme substrate complex. the substrate will bind specifically to the active site, facilitating chemical changes
how are enzymes selective about which reactions they catalyse
the substrate must fit precisely into the active site - as the substrate must be complementary to the active site of the enzyme - the lock and key model-
describe the stereospecific active site
is the substrate is chiral then only one enantiomer will have the correct stereochemistry to fit in the active site of the enzyme, so the reaction of one isomer is catalysed
how can drugs act as enzyme inhibitors
the drug will block the active site, stopping the substrate from binding.
some inhibitors (non-competitive) attach elsewhere on the enzyme causing the active site to change shape, so it is no longer complementary to the substrate
describe the structure of a nucleotide
phosphate group, pentose sugar and 1 of 4 nitrogenous bases ((adenine/thymine/cytosine/guanine)
how are nucleotides joined
phosphodiester bonds - these are covalent bonds between the phosphate of 1 nucleotide and the sugar of another nucleotide, creating a sugar phosphate backbone
describe the structure of DNA
two complementary strands arranged in a double helix
the bases are joined via complementary base pairing A+T and C+G
hydrogen bonding occurs between the bases, 2 between A+T and 3 between C+G
what is cisplatin
platinum based anti cancer drug.
complex of platinum with 2 chloride ions and 2 ammonia molecules
it targets cancer cells by attaching to the DNA, hindering ability to replicate, halting the growth of tumours
how does cisplatin prevent replication
ligand replacement reactions with DNA, when a dative covalent bond forms between the platinum and a nitrogen atom on guanine.
what is the effect of cisplatin on healthy cells
cisplatin can bind to healthy cells preventing them from replicating properly.
this leads to several side effects e.g. hair loss, suppressed immune system and kidney damage
how are side effects of cisplatin minimised
low dosage of cisplatin are given and further research is being done to ensure the target of the drug is more precise to cancer cells.
