It is classified as a polar, uncharged amino acid. The side chain of serine is a hydroxyl group (-OH).

Cysteine (Cys or C) is another amino acid with a different structure:


Cysteine is also a polar amino acid, but it is charged. The side chain of cysteine contains a sulfhydryl group (-SH). This sulfhydryl group can form covalent bonds with other cysteine residues, leading to the formation of disulfide bridges.

Key differences:

* The side chain of serine is a hydroxyl group, while the side chain of cysteine is a sulfhydryl group.

* Serine is uncharged, while cysteine is charged.

* Serine cannot form disulfide bridges, while cysteine can.