Which amino acid has a basic side chain and is commonly classified as diamino?

### Why this is right Lysine has an additional amino-containing group in its side chain, which can accept a proton and give the side chain a positive charge under physiological conditions. ### The other options - **Phenylalanine**: has a hydrophobic aromatic side chain. - **Valine**: has a nonpolar aliphatic side chain. - **Tyrosine**: has an aromatic side chain with a hydroxyl group, not a basic side chain. ### Terms - **Basic side chain**: a side chain that can accept a proton. - **Physiological conditions**: conditions similar to those inside the body. ### Remember Lysine and arginine are basic amino acids; aspartate and glutamate are acidic.