USA Biology Olympiad (USABO) Practice Exam

What is the primary function of a molecular chaperone?

1. To transport proteins across membranes

2. To bind to specific structures on the polypeptide and assist in folding

3. To degrade misfolded proteins

4. To catalyze biochemical reactions

The correct answer is: To bind to specific structures on the polypeptide and assist in folding

The primary function of a molecular chaperone is to bind to specific structures on a polypeptide and assist in its proper folding. Molecular chaperones play a crucial role in the protein folding process, ensuring that newly synthesized proteins achieve their correct three-dimensional structures, which is vital for their functionality. By binding to nascent or improperly folded polypeptides, chaperones can prevent aggregation and misfolding, which can lead to dysfunctional proteins or cellular stress. These chaperones often facilitate the folding process by providing an environment that stabilizes certain intermediate conformations, thus guiding the protein toward its native structure. Some chaperones may also participate in the unfolding and refolding of proteins under stress conditions, but their primary role revolves around assisting in the correct folding of proteins during and after their synthesis. Transporting proteins across membranes, degrading misfolded proteins, and catalyzing biochemical reactions are all essential cellular processes, but they are not the primary function of molecular chaperones. While some chaperones may interact indirectly with these processes, their main purpose is centered on ensuring that proteins fold correctly.