Ricin is incredibly heat tolerant.

• A. True
• B. Ricin is heat resistant
• C. Ricin is unaffected by heat
• D. False

Answer: (D)

Ricin is a protein toxin, and proteins can be inactivated by heat because heat denatures their structure, destroying the active sites needed for the toxin to work. Ricin has two components that work together to inhibit protein synthesis, and when exposed to sufficient heat, this structure is disrupted and its enzymatic activity is lost. So the idea that ricin is incredibly heat tolerant is not correct. It can be inactivated by heating, rather than remaining active under heat. The statement that it is immune to heat or unaffected by heat also conflicts with how protein toxins respond to heat, reinforcing that it is not heat-resistant.