[ plaz-muh-lem-uh ]
/ ˌplæz məˈlɛm ə /
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noun, plural plas·ma·lem·mas.Cell Biology.
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Origin of plasmalemma

1920–25; plasma + Greek lémma husk (see lemma2)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is a plasmalemma?

Plasmalemma is a less common 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. It is also called the plasma membrane.

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 plasmalemma. In general, a membrane is a thin barrier or covering. In the context of biology, plasma is used as another word for cytoplasm. The lemma in plasmalemma comes from a Greek word that means “husk.”

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 plasmalemma 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 plasmalemma.

Why is the plasmalemma important?

To understand why the plasmalemma is important, you first have to understand what it does. In essence, it serves as the glue that holds the components of the cell together and protects it from outside threats. The membrane regulates what comes into the cell. Among other things, it keeps potentially harmful substances out and keeps nutrients in.

The makeup of the plasmalemma includes three crucial components: phospholipids, cholesterol, and proteins. The phospholipids attract and repel water. The layer created by these opposing forces is known as the phospholipid bilayer. It’s responsible for creating the spaces within the membrane and making it a good barrier. Proteins help with transporting cell components across the barrier. Cholesterol also helps with this regulation.

Did you know ... ?

The understanding of the plasmalemma is based on what’s called the fluid mosaic model. The fluid mosaic model is a way of describing the structure of the cell membrane that likens it to a “mosaic” of different components, consisting of a fluid double layer of molecules. The model was developed by cell biologist S. J. Singer and biochemist Garth L. Nicolson in 1972. It has evolved somewhat since then, but it is now the most accepted way to understand the structure and function of the cell membrane.

What are real-life examples of plasmalemma?

Along with the nucleus and the cytoplasm, the plasmalemma is one of the main components of a cell. It’s more commonly called the cell membrane or the plasma membrane.


Quiz yourself!

True or False?

The plasmalemma blocks anything from entering.

British Dictionary definitions for plasmalemma


plasma membrane

/ (ˌplæzməˈlɛmə) /

other names for cell membrane
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for plasmalemma

[ plăz′mə-lĕmə ]

cell membrane
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.