🧬AP Biology
4. Myoglobin is a protein found in the muscle cells of mammals, where it facilitates the diffusion and storage of oxygen. To function correctly, myoglobin must be highly soluble in the aqueous environment of the cell cytoplasm. The protein consists of a single polypeptide chain that folds into a compact, globular tertiary structure.
The specific three-dimensional shape of myoglobin is determined by the sequence of amino acids in the polypeptide chain. The interactions between the side chains (R-groups) of these amino acids and the surrounding water molecules play a critical role in maintaining the protein's stability and solubility.
Describe the chemical property of the R-groups associated with the amino acids typically found in the interior core of a folded globular protein like myoglobin.
Explain how the polarity of water molecules influences the folding of the myoglobin polypeptide chain into its functional tertiary structure.
In a study of protein variants, researchers generated a mutant form of myoglobin where a specific glutamic acid residue (electrically charged and hydrophilic) located on the exterior surface of the protein was replaced by a valine residue (nonpolar and hydrophobic).
Predict the effect of the glutamic acid to valine substitution on the solubility of the mutant myoglobin in the aqueous cytoplasm.
Justify your prediction in part C.
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