9. What is the difference between a plasma membrane and a cell wall?

A plasma membrane and a cell wall are not the same thing. The plasma membrane, also called the cell membrane, is the outer membrane common to all living cells, made of a phospholipid bilayer, embedded proteins and some bound carbohydrates.

Because cell membranes are fragile, in some types of cells, there are also external structures to support and protect the membrane, like the cellulose wall of plant cells and the chitin wall of some fungi cells. Most bacteria also have an outer cell wall made of peptidoglycans and other organic substances.