Question

Which of the following is not true?

a. a zinc finger is considered a secondary structure
b. a protein domain is a structurally and functionally independent portion of a protein
c. the β-pleeted sheet is considered a secondary structure
d. the quartenary structure of a protein refers to how a single protein folds into four sections
e. ribbon diagrams are often used to illustrate the 3-diamentional structure of a protein.

Answer 1

The incorrect statement among the options provided is 'd. the quaternary structure of a protein refers to how a single protein folds into four sections', as the quaternary structure actually involves the arrangement of multiple polypeptide subunits, not the folding of a single protein into sections.

Step-by-step explanation:

The statement that is not true is: d. the quaternary structure of a protein refers to how a single protein folds into four sections. Quaternary structure actually refers to the arrangement of multiple polypeptide subunits and not the folding of a single protein into four sections.

Zinc fingers are indeed structural motifs involved in DNA recognition, and could be considered a secondary structure, though they're typically seen as a domain involving the tertiary structure as well. A protein domain is, as stated, a part of the protein that is structurally and functionally independent. The β-pleated sheet is recognized as a type of secondary structure, supported by hydrogen bonds between backbone amides in different strands. Lastly, ribbon diagrams are indeed commonly used to represent the three-dimensional structure of proteins and illustrate how the polypeptide chain folds into its secondary and tertiary structures.