The question requires us to define how the polarity of an amino acid can be determined.
The polarity of amino acids depends on different factors regarding the side chain, such as the electronegativity between bonded atoms and the presence of polar and non-polar groups in the side chain:
- the electronegativity: the bonds between atoms in the amino acid side chain is part of determining if the amino acid would be polar or non-polar. The greater the electronegativity between atoms in a bond, more polar will be the bond - and will contribute to increase the polar character of the amino acid.
- the presence of polar chains: polar side chains contains groups such as amines, amides an alcohols, and these groups can provide a more polar character to the amino acid.
- the presence (and quantity) of alkyl groups: on the contrary of the polar chains, alkyl groups (which present pure hydrocarbon chains) contribute to decrease the polar character of the amino acid.