Question

Protein domains are:

A) composed of multiple interacting polypeptides
B) a region within a polypeptide that has a specific structure and/or function
C) all positively-charged or all negatively charged amino acids
D) normally hydrophobic

Answer 1

Protein domains are regions within a polypeptide that have specific structures and/or functions. They are stable elements of a protein's overall structure and can be shared by different proteins. Protein domains contribute to the overall structure, stability, and functionality of proteins.

Step-by-step explanation:

Protein domains are regions within a polypeptide that have specific structures and/or functions. They are stable elements of a protein's overall structure that often fold independently of the rest of the protein chain. Domains can be shared by different proteins, and their names often reflect their biological function or the discoverer.

For example, the calcium-binding domain of calmodulin or the PH domain.

Proteins can have multiple domains, allowing them to perform various functions. Some domains may bind specific molecules, while others may have enzymatic activity.

Overall, protein domains contribute to the overall structure, stability, and functionality of proteins.

Answer 2

Protein domains are specific regions within a polypeptide with a distinct structure and function, and they can fold independently of the rest of the protein. Membrane proteins feature both hydrophobic and hydrophilic domains that determine their orientation and function within the cell membrane. The correct answer is options 2.

Step-by-step explanation:

A protein domain is a part of the protein's structure that is self-stabilizing and may fold independently from the rest of the protein chain. Domains are integral to proteins' functions and can be shared across different proteins, indicating evolutionary relationships within gene families and superfamilies. These domains can be involved in a multitude of biological roles, including cell signaling, molecular binding, and structural support within the cell. Despite being part of a larger polypeptide chain, these domains maintain specific three-dimensional structures that are crucial to their function.

Membrane proteins often have hydrophobic and hydrophilic domains. The hydrophobic domains are usually composed of alpha-helical regions that are compatible with the hydrophobic interior of cellular membranes. On the other hand, the hydrophilic domains typically face the aqueous environment, either inside or outside the cell, facilitating various interactions and functions such as signaling and transport. So, The correct answer is options 2.