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 that has a tertiary structure, meaning it folds into a compact, three-dimensional shape.
2. Recognize the nature of polar and nonpolar R groups: Polar R groups are hydrophilic, meaning they are attracted to water, while nonpolar R groups are hydrophobic, meaning they repel water.
3. Consider the environment of myoglobin: Myoglobin is found in muscle tissue, where it is surrounded by an aqueous (water-based) environment.
4. Predict the location of polar R groups: In the tertiary structure of myoglobin, polar R groups are likely to be located on the exterior surface of the protein, where they can interact with the surrounding water molecules.
5. Predict the location of nonpolar R groups: Conversely, nonpolar R groups are likely to be found in the interior of the protein, away from the aqueous environment, to minimize their exposure to water.

Key Concepts

Tertiary Structure of Proteins

The tertiary structure refers to the three-dimensional shape of a protein, formed by the folding of its 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, allowing them to interact with the aqueous environment. Understanding this effect is vital for predicting the arrangement of amino acids in the tertiary structure.