The cell or "plasma" membrane is described as a Fluid Mosaic Model. Can you explain what this means?

The fluid mosaic model describes the cell membrane as a tapestry of several types of molecules (phospholipids, cholesterols, and proteins) that are constantly moving. This movement helps the cell membrane maintain its role as a barrier between the inside and outside of the cell environments.

Explanation:

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?