Final answer:
The side chain of serine is polar and contains a hydroxyl group. It can form hydrogen bonds and is able to be phosphorylated.
Step-by-step explanation:
The side chain of the amino acid serine (S) is polar and can form hydrogen bonds. It contains a hydroxyl group (-OH) which makes it hydrophilic or water-loving.
Serine can also be phosphorylated, meaning a phosphate group can be added to its side chain. This phosphorylation affects protein function by modifying its structure and signaling.