section 2: biological molecules - topic 5: proteins Flashcards
what are proteins?
polymers.
what are the monomers of proteins?
amino acids.
what is formed when 2 amino acids join together?
a dipeptide.
what is formed when more than 2 amino acids join together?
a polypeptide.
what are proteins made up of?
one or more polypeptides.
what is the general structure of all amino acids?
a carboxyl group (-COOH) and an amino group (-NH2) attached to a carbon atom.
what is the difference between different amino acids?
the variable group they contain.
what chemical elements do all amino acids contain?
carbon.
oxygen.
hydrogen.
nitrogen.
some also contain sulphur.
what are amino acids linked together by?
peptide bonds - to form dipeptides and polypeptides.
what type of reaction is it to form dipeptides and polypeptides?
a condensation reaction.
^ a molecule of water is released during the reaction.
the reverse of this adds a molecule of water to break the peptide bond.
- hydrolysis reaction.
what are the 4 structural levels of a protein?
primary.
secondary.
tertiary.
quaternary.
describe the primary structure.
- this is the sequence of amino acids in the polypeptide chain.
- different proteins have different sequences of amino acids in their primary structure.
- a change in just 1 amino acid may change the structure of the whole protein.
- it’s held together by the peptide bonds between the amino acids.
describe the secondary structure.
- the polypeptide chain doesn’t remain flat and straight.
- hydrogen bonds form between the -NH and -CO groups of the amino acids in the chain.
- this makes it automatically coil into an alpha helix or fold into a beta pleated sheet.
describe the tertiary structure.
- the coiled or folded chain of amino acids is often coiled and folded more.
- more bonds form between different parts of the polypeptide chain.
what are the bonds involved in the tertiary structure?
ionic bonds.
disulphide bonds.
hydrophobic & hydrophilic interactions.
hydrogen bonds.