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.
Definition of circle for English Language Learners. : 1  a perfectly round shape : a line that is curved so that its ends meet and every point on the line is the same distance from the center. : 2  a path that goes around a central point. : 3  an arrangement of people or things that forms a circle.