Compare a bituminous roof membrane to a single ply roof membrane.

Single-ply membranes are a assorted and promptly increasing group of sheet materials that are functional to the roof in a single layer. As equated to built-up membranes, they need less on-site labor, and they are usually more flexible and therefore less liable to to cracking and ripping. They are attached to the roof surface by any of several means.

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.