Question

"Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term 'protein domain.'"

A. A specific sequence of amino acids in a protein.
B. A distinct, independently folding structural unit within a protein.
C. The three-dimensional arrangement of multiple protein molecules.
D. The overall shape of a protein in its functional state.

Answer 1

The term 'protein domain' best corresponds to a distinct, independently folding structural unit within a protein, essential for protein function and stability. Each domain can have a specific role, such as DNA binding or enzymatic activity. The correct option is B. A distinct, independently folding structural unit within a protein.

Step-by-step explanation:

When considering the different levels of protein structure, such as the primary, secondary, tertiary, and quaternary levels, a protein domain refers to a specific part of a protein sequence that can fold independently into a stable three-dimensional structure.

Out of the provided definitions, the one that best fits the term 'protein domain' is B. A distinct, independently folding structural unit within a protein.

Protein domains are crucial for the function of a protein because they often serve as modules with a specific function. For example, some domains are responsible for binding DNA, while others might be responsible for enzyme activity or molecule binding.

This understanding of protein domains helps in predicting the function of unknown proteins and understanding the effects of mutations. The correct option is B. A distinct, independently folding structural unit within a protein.