Is phenylalanine hydrophilic or hydrophobic? Explain why.

Verified step by step guidance

1. Phenylalanine is an amino acid with a side chain that contains a benzyl group (a benzene ring attached to a CH2 group). To determine if it is hydrophilic or hydrophobic, we need to analyze the properties of its side chain.
2. Hydrophilic molecules or groups are typically polar or charged, meaning they can interact with water through hydrogen bonding or ionic interactions. Hydrophobic molecules or groups are nonpolar and do not interact well with water.
3. The benzyl group in phenylalanine's side chain is nonpolar because the benzene ring is composed of carbon and hydrogen atoms, which share electrons relatively equally, resulting in no significant polarity.
4. Since the side chain of phenylalanine is nonpolar, it does not form hydrogen bonds or interact favorably with water. This makes phenylalanine hydrophobic.
5. In summary, phenylalanine is hydrophobic because its side chain is nonpolar and does not interact well with water.

Key Concepts

Hydrophilicity and Hydrophobicity

Hydrophilicity refers to the tendency of a molecule to interact favorably with water, often due to the presence of polar or charged groups. In contrast, hydrophobicity describes a molecule's aversion to water, typically associated with nonpolar structures. Understanding these properties is crucial for predicting how substances behave in biological systems, particularly in relation to solubility and interaction with cellular membranes.

Amino Acid Structure

Amino acids, the building blocks of proteins, have a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group (side chain). The nature of the R group determines the amino acid's properties, including whether it is hydrophilic or hydrophobic. In the case of phenylalanine, its aromatic side chain contributes to its hydrophobic characteristics.

Phenylalanine's Chemical Properties

Phenylalanine is an aromatic amino acid with a nonpolar side chain, which makes it hydrophobic. The presence of the benzyl group in its structure prevents it from forming hydrogen bonds with water, leading to its preference for nonpolar environments. This property is significant in protein folding and function, as hydrophobic interactions play a key role in stabilizing protein structures.