Amino Acid Side Chain Properties: Polarity, Charge, and Zwitterionic State

To determine the polarity, charge, and zwitterionic state of an amino acid side chain, we need to know the specific amino acid in question. Here's a breakdown of the steps involved:

1. Identify the Side Chain: Each amino acid has a unique side chain (also known as an R-group) that determines its properties.
2. Polarity:
   • Polar: Side chains that are hydrophilic (water-loving) and can form hydrogen bonds are considered polar. Examples include serine (Ser), threonine (Thr), and asparagine (Asn).
   • Nonpolar: Side chains that are hydrophobic (water-fearing) and do not readily form hydrogen bonds are considered nonpolar. Examples include alanine (Ala), valine (Val), and leucine (Leu).
3. Charge:
   • Acidic: Side chains that contain a carboxyl group (COOH) are acidic. They can lose a proton (H+) to become negatively charged at high pH. Examples include aspartic acid (Asp) and glutamic acid (Glu).
   • Basic: Side chains that contain an amino group (NH2) are basic. They can gain a proton (H+) to become positively charged at low pH. Examples include lysine (Lys), arginine (Arg), and histidine (His).
4. Zwitterionic State:
   • Zwitterion: At a specific pH (the isoelectric point), amino acids exist as a zwitterion, meaning they have both a positive and negative charge. The pH at which this occurs depends on the specific amino acid.
5. Positive and Negative Charge Ranges:
   • Positively Charged: At pH values below the isoelectric point, the amino acid will have a net positive charge.
   • Negatively Charged: At pH values above the isoelectric point, the amino acid will have a net negative charge.

To answer the questions about a specific side chain, please provide the name of the amino acid or its three-letter code (e.g., 'Ala' for alanine).