are receptor molecules on mammalian cells that recognize macromolecules that are present in or on certain groups of pathogens.

Toll like receptors

Explanation:

They are proteins and produce the required signals in the innate immune system. They help in identifying the molecular structure and composition of pathogens.The signals they give results in inflammatory response.

this allows people to make the best decision or pursue the best option. when alternatives are weighed using their advantages and disadvantages, the option whose disadvantages outweigh the advantages (based on a qualitative or quantitative analysis) are shunned while those whose advantages outweigh their disadvantages are pursued.  

your answer is, orbit around the nucleus