Which amino acid is hydrophilic (dissolves in aqueous solutions)? Why?


a. isoleucine
b. phenylalanine
c. aspartic acid

Verified step by step guidance

1. Identify the nature of each amino acid: hydrophilic or hydrophobic.
2. Understand that hydrophilic amino acids have side chains that can form hydrogen bonds with water.
3. Analyze the side chain of isoleucine: it is nonpolar and hydrophobic.
4. Analyze the side chain of phenylalanine: it is nonpolar and hydrophobic.
5. Analyze the side chain of aspartic acid: it contains a carboxyl group, which is polar and can form hydrogen bonds, making it hydrophilic.

Key Concepts

Hydrophilicity

Hydrophilicity refers to the property of a molecule that allows it to interact favorably with water. Hydrophilic substances tend to be polar or charged, enabling them to form hydrogen bonds with water molecules, which facilitates their dissolution in aqueous solutions. This property is crucial in biological systems, as it affects how molecules interact within cells and in bodily fluids.

Amino Acid Structure

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid has a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). The nature of the R group determines the amino acid's properties, including whether it is hydrophilic or hydrophobic, influencing protein structure and function.

Polar vs. Nonpolar Side Chains

The side chains of amino acids can be classified as polar or nonpolar, which significantly impacts their solubility in water. Polar side chains contain electronegative atoms, such as oxygen or nitrogen, making them hydrophilic and capable of forming hydrogen bonds with water. In contrast, nonpolar side chains are hydrophobic and do not interact well with water, affecting the overall behavior of proteins in aqueous environments.