Impact of Amino Acid Substitution on Protein Structure

Amino acids are the building blocks of proteins, and their sequences determine the structure and function of proteins. Each amino acid has a unique side chain, also known as a R group, which affects its chemical properties. For example, some amino acids are hydrophobic, while others are polar or charged.

Consider the following scenario: A researcher is studying a protein that is composed of a sequence of amino acids. The protein has a hydrophobic core that stabilizes its structure by minimizing exposure to the aqueous environment. Additionally, the researcher finds that altering a single amino acid in the protein's sequence disrupts its function significantly.

Which of the following amino acids, if replaced by a hydrophilic amino acid, is most likely to result in the disruption of the protein's structure and function?