What's the difference b/w adding 5 mL of trypsin versus just enough to cover the monolayer for cell culture? I've always been taught to add the set amount and let the cells incubate. But I've been hearing from some people that its better to add just enough trypsin so that the cells are covered and then letting it incubate. What's the difference? (P.S. the cell lines I'm working with are Hep3B, Ht-29, and Hela cells)