How do you disassociate contacts from an opportunity in the opportunity module?

How do you disassociate contacts from an opportunity in the opportunity module?

Working in the Opportunity module within CRM, I have several contacts associated with an opportunity.  A couple have left the company or moved departments and I want to disassociate them and add their replacements.

Adding new folks isn't an issue, but I don't see a way to disassociate the old contacts.  There seems to be no way to do that within the opportunity module and if I go to the contact itself and delete from its opportunity list, the entire opportunity is deleted.  

There are Assign and Unassign button for opportunities in the Organization module to allow you to link or unlink opportunities to organizations.  There are even link and unlink options for individual emails.  

But I don't see anything like that for Contacts.

Help is appreciated.