Polar R Groups

Introduction to Protein Structure

Polar Amino Acids

The side chains (R groups) of the amino acids can be divided into two major classes, those with polar side chains (shown here) and those with nonpolar side chains.

The polar amino acids include: arginine, asparagine, aspartic acid (or aspartate), glutamine, glutamic acid (or glutamate), histidine, lysine, serine, and threonine.

Polar side chains contain groups that are either charged at physiological pH or groups that are able to participate in hydrogen bonding. Exam each of the amino acids shown below and determine why it is considered polar.

Name	3 letter code	1 letter code	2-D Structure	3-D Structure
Arginine	Arg	R		C_a: Model:
Asparagine	Asn	N		C_a: Model:
Aspartate	Asp	D		C_a: Model:
Glutamine	Gln	Q		C_a: Model:
Glutamate	Glu	E		C_a: Model:
Histidine	His	H		C_a: Model:
Lysine	Lys	K		C_a: Model:
Serine	Ser	S		C_a: Model:
Threonine	Thr	T		C_a: Model: