Amino Acids and pH

Two amino acids have acidic side chains at neutral pH. These are aspartic acid or aspartate (Asp) and glutamic acid or glutamate (Glu). Their side chains have carboxylic acid groups whose pKa’s are low enough to lose protons, becoming negatively charged in the process. There are three amino acids that have basic side chains at neutral pH. These are arginine (Arg), lysine (Lys), and histidine (His). Their side chains contain nitrogen and resemble ammonia, which is a base. Their pKa’s are high enough that they tend to bind protons, gaining a positive charge in the process. Keywords: In a neutral solution, most amino acids exist as: A) positively charged compounds. B) zwitterions. C) negatively charged compounds. D) hydrophobic molecules. At pH 7, the charge on a glutamic acid molecule is: A) –2 B) –1 C) 0 D) 1 #AcidicAminoAcids #BasicAminoAcids #Polypeptides #protein #PH