Undergrad vs Graduate Work

What is the difference between undergrad and grad students in professional interaction? I explained it recently to a student as follows:

•  In undergrad times, the interactions are transactional/negotiation-oriented: professor gives you HWs, you do them, you get points;  professor poses a problem, you answer it, get points, you dont answer it, say the problem was confusing, get partial points; at the end of the course, you get a grade, forget the professor,  approach the professor again when you need a reference letter, professor writes a more or less generic letter saying you were one of the top X students in the class or whatever; your life moves on, the professor stays behind. 
• In grad times, the interactions are relational: you take a course with a professor and do well or not; you might continue research with the professor or have them on your qualifier exam; you will TA one of their courses later or even be a GA if that professor has funds and your advisor needs some gap funding; that professor might have a contact in a company looking for a research intern for a summer and they might connect you;  they might ask you to referee papers or recommend you for a travel grant; even if your research diverges from that professor, you might remember something about that professor's research which helps you during an interview, just being world-aware; etc. your life moves on, so does the professor's, and two professional research lives, even if parallel, will cross in unexpected ways.