Prokaryotes have only one lipid bilayer- the cell membrane (also known as the plasma membrane). Many prokaryotes also have a cell wall, but the cell wall is composed of proteins or long chain carbohydrates, not lipids.
3. countable noun. A wedge is an object with one pointed edge and one thick edge, which you put under a door to keep it firmly in position. 4. countable noun. A wedge is a piece of metal with a pointed edge which is used for splitting a material such as stone or wood, by being hammered into a crack in the material.
Learner's definition of WEDGE. [count] 1. : a piece of wood, metal, etc., with one pointed end and one thicker end that is used to split something, to fit into a space, to separate two things stuck together, etc. He used a wedge to split the firewood. A wedge held the door open.