Which amino acids are described as basic because their side chains are positively charged?

1. The chemical nature of the side chain decides whether an amino acid is acidic, basic, polar or nonpolar. 2. The side chains of lysine and arginine carry a positive charge. 3. That positive charge is why they are known as basic amino acids. 4. Serine, threonine and cysteine are polar with hydrophilic side chains rather than charged. 5. Valine, methionine and alanine are nonpolar or hydrophobic, so they sit at the other end of the scale. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 3 "Biological Macromolecules", section 3.4 Proteins_