Proteins are essential biomolecules that play critical roles in biological systems. They are composed of long chains of amino acids linked together by peptide bonds. An amino acid consists of an amino group, a carboxyl group, and a unique side chain (R group) that determines the properties of the amino acid. Each type of amino acid has a distinct side chain, which can be polar, non-polar, acidic, or basic.
Consider the following amino acids: glycine (which has a hydrogen atom as its side chain), alanine (with a side chain that is a methyl group), aspartic acid (which has a carboxyl group as its side chain), and lysine (with an amino group as its side chain). Based on the properties of these amino acids, which statement is true?