Final answer:
Endospores are resistant to heat because they have little water, contain unique protective chemicals in the spore wall, and are dormant, reducing damage from heat compared to vegetative cells. The correct answer are options a,b,d.
Step-by-step explanation:
Endospores are highly resistant structures formed by certain bacteria as a mean to survive extreme environmental conditions. The robustness of endospores against heat, as opposed to more vulnerable vegetative cells, can be attributed to several factors. One key reason is that endospores contain very little water, which decreases the efficiency of heat to denature proteins and DNA within them. Additionally, endospores have unique chemicals in their spore wall, such as calcium and dipicolinic acid, that enhance their heat resistance beyond what is seen in vegetative cell walls. Finally, the dormancy of the spore means that metabolic reactions are halted, making them less susceptible to heat-induced damage that active cells might experience. It is worth noting that the absence of proteins mentioned in the options as 'promins' seems to be a typo, since proteins do play a role in endospores, but the principle stand true that the types of proteins present in endospores are less likely to denature due to the unique protective environment within the spore.
The correct options that explain why endospores are not killed easily by heat are: a) little water in an endospore compared to a vegetative cell, b) unique chemicals within the spore wall that make it more resistant to heat than vegetative cells walls, and d) dormancy of the spore.