I found some information about sysprotects and syspermissions in technet here is the text:

The implementation of the sysprotects system table has changed. In SQL Server 7.0 and earlier, the sysprotects table stored the object permissions. In SQL Server 7.0, this information is now stored in the syspermissions table.
In most cases, where the implementation of a system table changed, Microsoft provided a view that provided backward compatibility. One example of this is the implementation of the master..sysxlogins table; the syslogins view is now provided for backward compatibility.

In the case of the sysprotects system table, however, the change in the underlying system table was much more major, and a view was not able to provide backward compatibility efficiently. For this reason, Microsoft opted not to implement a sysprotects view, but to create a special table named sysprotects, which appears as a normal table to the system, but is really created dynamically when required.

The sysprotects table is therefore somewhat like a view, as it does not actually have any persisted data pages. However, because the view-like behavior is implemented in the database engine, the sysprotects object appears as a table in the sysobjects table.