In myoglobin, about one-half of the 153 amino acids have nonpolar R groups.
b. Where would you expect the polar R groups to be in the tertiary structure?

Verified step by step guidance

1. Understand the structure of myoglobin: Myoglobin is a globular protein with a tertiary structure, meaning it folds into a three-dimensional shape. This folding is influenced by the properties of the amino acid side chains (R groups).
2. Recall the properties of polar and nonpolar R groups: Polar R groups are hydrophilic (water-attracting), while nonpolar R groups are hydrophobic (water-repelling). This distinction plays a key role in protein folding.
3. Consider the environment of the protein: Myoglobin is found in aqueous (water-based) environments, such as inside cells or tissues. Proteins in such environments tend to arrange their polar and nonpolar R groups strategically.
4. Apply the principle of hydrophobic and hydrophilic interactions: Nonpolar R groups are typically buried in the interior of the protein to avoid contact with water, while polar R groups are usually exposed on the surface of the protein to interact with the surrounding water molecules.
5. Conclude the expected location of polar R groups: Based on the principles of protein folding, you would expect the polar R groups to be located on the exterior of the tertiary structure of myoglobin, where they can interact with the aqueous environment.

Key Concepts

Tertiary Structure of Proteins

The tertiary structure of a protein refers to its three-dimensional shape formed by the folding of the polypeptide chain. This structure is stabilized by various interactions, including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. Understanding the tertiary structure is crucial for predicting how a protein will function and interact with other molecules.

Polar and Nonpolar Amino Acids

Amino acids can be classified based on the properties of their R groups (side chains) as polar or nonpolar. Nonpolar R groups tend to be hydrophobic and are usually found in the interior of proteins, away from the aqueous environment, while polar R groups are hydrophilic and often located on the exterior, interacting with water. This distribution is essential for the protein's stability and function.

Hydrophobic Effect

The hydrophobic effect is a key driving force in protein folding, where nonpolar amino acids aggregate to minimize their exposure to water. This phenomenon leads to the formation of a stable core in the protein structure, while polar amino acids are positioned on the surface, facilitating interactions with the aqueous environment. Understanding this effect helps explain the arrangement of amino acids in the tertiary structure.