Question

How can proteins survive at temperatures as high as 100 degree celsius in a living system?

Answer 1

The melting temperature varies for different proteins, but temperatures above ${41}^{\circ }C\left({105.8}^{\circ }F\right)$ will break the interactions in many proteins and denature them. This temperature is not that much higher than normal body temperature $\left({37}^{\circ }Cor{98.6}^{\circ }F\right)$, so this fact demonstrates how dangerous a high fever can be.
Ahyperthermophileis an organism that thrives in extremely hot environments - from ${60}^{\circ }C\left({140}^{\circ }F\right)$ upwards. An optimal temperature for the existence of hyperthermophiles is above ${80}^{\circ }C\left({176}^{\circ }F\right)$. Hyperthermophiles are a subset of extremophiles, micro-organisms within the domain Archaea, although some bacteriaare able to tolerate temperatures of around ${100}^{\circ }C\left({212}^{\circ }F\right)$, as well. Some bacteria can live at temperatures higher than ${100}^{\circ }C$ at large depths in sea where water does not boil because of high pressure.
So the conclusion will be, in the organisms which survive at ${37}^{\circ }C$ or ${98.6}^{\circ }F$, their proteins will get denatured above ${41}^{\circ }C\left({105.8}^{\circ }F\right)$ except hyperthermophiles which can tolerate high temperatures.