Amino acid - Building Blocks, Structure, Functions | Britannica
Identifying amino acid side chains as polar, non-polar or charged - Real Chemistry - YouTube
PROPERTIES OF THE 20 AMINO ACIDS
How to know if an amino acid is polar or nonpolar - Quora
II- Classification according to polarity of side chain (R): A- Polar amino acids: Polar side chains contain groups that are either charged at physiological. - ppt download