Final answer:
Molecular chaperones, catalytic proteins (enzymes), and regulatory proteins are vitally important to cell function in all types of stressful circumstances.
Step-by-step explanation:
Proteins that are vitally important to cell function in all types of stressful circumstances include molecular chaperones, catalytic proteins, and regulatory proteins. Molecular chaperones help other proteins fold correctly and prevent them from clumping together. Catalytic proteins, also known as enzymes, speed up chemical reactions in cells. Regulatory proteins control gene expression and cellular processes, helping cells adapt to stress.