Amino acids and proteins
- amino acids have one amino group (NH2) and one acid group (COOH)
- they have an R group e.g. CH3
- another adjacent hydrogen on a carbon
Amino acids are an example of bi-functional compound - compounds with two functional groups which interact with each other.
- the proton donating -COOH and proton accepting -NH2 react with one another, forming a zwitterions.
- a zwitterion = particles containing both negatively charged and positively charged groups.
An aqueous solution of an amino acid consists mainly of zwitterions, with very few molecules containing the un-ionised groups. Amino acids and very soluble in water because they are effectively ionic!
UNLESS there is an extra -COOH or -NH2 group in the molecule then the solution is neutral in aqueous solution.
- amino acids can act as a buffer solution.
- a buffer solution can withstand the addition of small amounts of acid or alkali.
- the zwitterions neutralise the effect of addition.
Making peptides and proteins