Essential amino acids
Different amino acid molecules can be joined together in different orders within our bodies to form different proteins.
The body cannot make all the amino acids required to build different proteins. It relies on protein intake from our diet to supply the essential amino acids.
Amino acids can then be used in sequence to build up protein in the body.
Breaking down proteins
Similar to esters, protein molecules can be broken down by hydrolysis (the opposite of condensation). Water molecules break apart the peptide links of the protein molecule, leaving separate amino acid molecules.
Given the structure of a protein molecule, the structures of the amino acids used to form it can be shown by simply breaking every peptide link to leave amine and carboxyl groups.
Digestion of proteins
During digestion, enzymes in our bodies break the proteins we eat down into amino acids (by hydrolysis).
These amino acids are transported around the body by blood. In the bloodstream, condensation reactions build the amino acids up to produce proteins required by the body.