Lecture 4 Flashcards
Building blocks of proteins
How many different amino acids are there?
20
What do amino acids contain?
Basic amino group, acidic carboxyl group
The alpha carbon of an amino acid is a…?
Chiral compound
Define chirality
Non-superimposable mirror images on a compound
Amino acids act as __ in solution
Zwitterions
Define a zwitterion
An ion existing with a +ve and -ve charge at the same time
Amino acids differ by…?
Their side chain (R group)
What are the four classes of amino acid?
Non-polar, Polar uncharged, Polar positive, Polar negative
What is the water associated nature structure of most proteins?
Hydrophobic (non-polar) group gets buried within the core in order to stabilise the protein. Hydrophilic (polar) group lies on the exterior
Why is the hydrophilic component of a protein generally exposed?
It requires energy to bury a charge. It is tied up with salt links and H-bonds as well as residues of oppositely charged residues to neutralise the charge
What is different about glycine?
It is not chiral as it’s side chain is a singular H, this makes is relatively flexible
What is different about Proline?
Side chain bonds back to the main chain N forming an imino acid which is much more rigid
What are the name forms that amino acids exist as?
three and one letter abbreviations
Why are one letter abbreviations useful?
Helps to describe sequence alignment and mutations
What does ‘E6V’ mean?
There is a mutation of glutamate to a valine at position 6 in the protein sequence
What amino acids can act as acids and bases?
Amino acids with ionisable side chains where a proton can be donated or accepted
What is pKa
the pH at which the group is 50% ionised
What is pL
the pH at which the net charge on a amino acid is zero (isoelectric point)
What is the general pKa values for the carboxyl and amino groups respectively?
~2 and ~10
What are modified amino acids?
Amino acid derivatives that are created in-house
What is translation?
The translation of RNA to proteins at the ribosome
What is ‘post-translational modification’
When the amino acid is modified after they are added to a protein
What is an example of post-translational modification?
The disulphide bond
What are some other amino acid modifications?
Phosphorylation, hydroxylation, carboxylation, metal binding, iodination, glycosylation
