plasma membrane

noun

Cell Biology.

1. cell membrane.

plasma membrane

1. See cell membrane

Word History and Origins

Origin of plasma membrane¹

First recorded in 1895–1900

When To Use

What is a plasma membrane?

Plasma membrane is another term for the cell membrane—the thin layer that encloses a cell’s cytoplasm, which is the substance between the membrane and the nucleus. It allows beneficial things to pass through while blocking harmful ones.The cell is the basic structural unit of all living organisms. It is a microscopic structure consisting of a nucleus surrounded by the cytoplasm and enclosed by a membrane—the plasma membrane. In general, a membrane is a thin barrier or covering. In the context of biology, plasma is used as another word for cytoplasm.The membrane consists of a double layer made up of lipid molecules and large protein molecules. Lipids and proteins are the basic building blocks of living cells. They move fluidly in the plasma membrane and function like a system of gates, giving the membrane its ability to allow molecules to pass through. For this reason, the membrane is described as semipermeable (meaning it is capable of allowing things to pass through it).Plants cells also have a rigid outer wall in addition to a plasma membrane.The plasma membrane is also called the plasmalemma.