Why is it entitled "The Merchant of Venice"?
Everyone seems to be focusing on Shylock and other characters as the main focus of the play, but we need to consider that Shakespeare named the play The Merchant of Venice, referring to Antonio, and he did so for a reason.
My personal opinion is that the play starts with Antonio, and then several storylines branch out from him (Bassanio's, Portia's, Jessica's, Shylock's, etc.). These storylines then continue pretty much without Antonio's presence (except that little scene 3 we did our essay on). When the storylines all converge, it is when Antonio is in trouble at the trial. He also is present, though not a major player, in the resolution scene. He seems to me to be the Nick Carraway of the play (The Great Gatsby), where a lot of stuff happens around him, but he is not the most important or most interesting character in the events. Also, just like Nick, his character seems to determine the course of events and have an indirect influence on most of the play.