Question

Which of the following is true about the different structures of protein?

• A. Secondary structure is the three-dimensional structure of protein
• B. Secondary structure is stabilized by disulfide bonds
• C. Primary, secondary and tertiary structures are destroyed during denaturation
• D. Secondary and tertiary structure depend on the sequence of amino acids

Hint:

The sequence written first decides every fold that follows.

Answer 1

The Correct Option is D

Work this one by knocking out the false statements one at a time. Statement (a) calls the secondary structure the three-dimensional shape, but the full 3D fold of a single chain is the tertiary level, so that is wrong. Statement (b) says disulfide bonds stabilize secondary structure, yet secondary structure (helices and sheets) is held together by backbone hydrogen bonds, while disulfide bridges between cysteines stabilize the tertiary fold, so that is wrong too. Statement (c) claims denaturation destroys the primary structure, but denaturation only unravels the higher-order folds; peptide bonds stay intact, so the primary sequence survives, making it wrong. That leaves statement (d), which is the central dogma of protein folding: the order of amino acids in the primary sequence carries all the information needed for the chain to fold into its secondary and tertiary forms. Hence (d) is the true statement.