20 Common Amino acids You should know names, structures, pka values, 3-letter and -letter codes Non-polar amino acids Polar, uncharged amino acids Acidic amino acids Basic amino acids20 Common Amino Acids You should know names, structures, pKa values, 3-letter and 1-letter codes • Non-polar amino acids • Polar, uncharged amino acids • Acidic amino acids • Basic amino acids