Which amino acids are considered non-polar?

The selection of glycine, alanine, and tryptophan as non-polar amino acids is accurate because these amino acids primarily contain hydrocarbon side chains, which contribute to their non-polar characteristics.

Glycine, being the simplest amino acid, has a hydrogen atom as its side group, making it the most non-polar due to lack of a bulky side chain. Alanine features a methyl group as its side chain, also a non-polar structure. Tryptophan, although slightly more complex due to its indole ring, still has a predominantly non-polar structure despite having a nitrogen atom in its side chain that can participate in hydrogen bonding.

In contrast, the other choices consist of amino acids that possess polar or charged side chains. Serine and threonine have hydroxyl groups that make them polar, while histidine can carry a positively charged nitrogen group under physiological conditions. Cysteine contains a thiol group (-SH), which is also polar. Asparagine and glutamine have amide groups that enhance their polar nature. Arginine and lysine are basic amino acids with positively charged side chains, and glutamate is negatively charged at physiological pH. These traits facilitate interactions with other polar molecules