Latches and mutexes may only protect access to memory structures if they are accessed by processes in the same instance. In RAC, latches and mutexes are still used, but for global concurrency control, some additional global enqueues are used to provide protection across instances. Oracle requires concurrency control because it is a multi-user system. Single-instance Oracle provides concurrency control:

Latches or mutexes for memory structures
Enqueues for resource control
Buffer cache pins for cache management

BEF correct