Hi Shaista,
In agreement with Youssef - you can classify each amino acid based on their characteristic side chain. The properties of these side chains are essential for the function of proteins, so it is a high yield MCAT topic!
You can break them down into 4 groups... polar, non-polar, acidic (polar negative charge) and basic (polar positive charge).
Non-Polar: These side chains are considered nonpolar due to their aliphatic nature; they are primarily composed of carbons and hydrogens. These amino acids include glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan and proline. Note that due to their nonpolar nature, these amino acids will not be attracted to water surrounding the protein, and as such they will often located in the core of proteins to aggregate away from unfavourable interactions with water.
Polar: The polar amino acids are serine, threonine, cysteine, tyrosine, asparagine and glutamine. The polar AAs will often be positioned on the outside of the protein to interact with water.
Acidic: There are two acidic amino acids: aspartate and glutamate. These residues are proton donors. They will often lose a proton in solution becoming negatively charged.
Basic: There are three basic amino acids: lysine, arginine, and histidine. These residues are proton acceptors. Each of these basic amino acids has a nitrogen that can accept a hydrogen to become positively charged.