How to remove extra tabs in Buyer Work Center?

We are upgrading from 12.1.3 to 12.2.5.  In 12.1.3, in the Buyer Work Center, we only show 4 tabs -- Requisitions, Orders, Agreements, and Suppliers.  In 12.2.5, there are extra tabs visible -- IDVs, Negotiations, Awards -- which we want to remove.  We also want to hide the New Supplier Requests and Supplier Profile Update Requests links on the Suppliers tab.  These are not visible in 12.1.3, as the buyers do not manage the suppliers and should have view-only access.

Thanks,

Heidi