Impact of deprecated std::unary_function and std:: binary_function?

std::unary_function and std::binary_function were depreacated in c++11. I have two doubts.

1. Does std::unary_function or std::binary_function come into play only if function is explicitly derived from them. like this:

struct derivedsmthing:  std::unary_function<smthing> ?

2. if not, i.e. some functions will get impacted even if it's not explicitly derived from these two? what are those functions?