cell membrane

[ sel mem-breyn ]


, Biology.
  1. the semipermeable membrane enclosing the cytoplasm of a cell.

cell membrane


  1. a very thin membrane, composed of lipids and protein, that surrounds the cytoplasm of a cell and controls the passage of substances into and out of the cell Also calledplasmalemmaplasma membrane

cell membrane

  1. The thin membrane that forms the outer surface of the protoplasm of a cell and regulates the passage of materials in and out of the cell. It is made up of proteins and lipids and often contains molecular receptors. The membranes of organelles within the cell are made of the same basic material as the cell membrane. In plant cells, the cell membrane is surrounded by a rigid cell wall.
  2. Also called plasma membrane
  3. Compare cell wallSee more at cell

cell membrane

  1. The structure separating an animal cell from its environment or a plant cell from its cell wall . The cell membrane is a complex system that allows nutrients to enter the cell and waste products to leave, usually through osmosis .

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Word History and Origins

Origin of cell membrane1

First recorded in 1865–70

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Compare Meanings

How does cell membrane compare to similar and commonly confused words? Explore the most common comparisons:

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Example Sentences

Other types of bacteria have double cell membranes—an inner and an outer layer.

This electrical impulse is made by waves of charged particles weaving in and out of the cell membrane, rippling the signal along.

Examples include nucleotides, the building blocks of DNA and RNA, and phosphocholine, a precursor to the lipid molecules that make up the cell membrane.

These receptors are embedded into the artificial cell membrane.

As Hertle watched, the proto-plastids crawled along the inside of the cell membrane to positions beneath the newly discovered holes in the cell wall.

No breathing organs are seen, because osmosis of oxygen and carbon dioxide may take place anywhere through the cell membrane.

Meanwhile great advances had been made also in the knowledge of the mature framework of cell-membrane in plants.

They consist of a minute droplet of protoplasm (mycroprotein) surrounded by a delicate cell membrane.

The outer covering, or cell membrane, of the globular egg remains undivided.

We may also obtain cells with cytoplasm filling the whole of the cellular cavity or separated from the cell-membrane.


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More About Cell Membrane

What is a cell membrane?

The cell membrane is 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 cell membrane. In general, a membrane is a thin barrier or covering.

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 cell 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 cell membrane.

The cell membrane is also called the plasma membrane or the plasmalemma.

Why is the cell membrane important?

To understand why the cell membrane is important, you first have to understand what it does. In essence, the cell membrane 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 cell membrane 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 cell membrane is based on what’s called the fluid mosaic model. The fluid mosaic model is a way of describing the structure of cell membranes that likens them 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 cell membrane?

Along with the nucleus and the cytoplasm, the cell membrane is one of the main components of a cell. It’s familiar to many biology students.

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Quiz yourself!

True or False?

The cell membrane blocks anything from entering.




cell-mediated immunitycello