Plasma Membrane

The membrane, which covers the surface of a cell and other internal cellular organelles are termed the membrane.

What is Plasma Membrane?

An outermost envelope-like membrane or a structure, which surrounds the cell and its organelles is called the plasma membrane. It is a double membraned cell organelle, which is also called the phospholipid bilayer and is present both in prokaryotic and eukaryotic cells.

In all living cells, the plasma membrane functions as the boundary and is selectively permeable, by allowing the entry and exit of certain selective substances. Along with these, the plasma membrane also acts as a connecting system by providing a connection between the cell and its environment.

Explore more: Cell organelles

Structure of Plasma Membrane

A plasma membrane is mainly composed of carbohydrates, phospholipids, proteins, conjugated molecules, which is about 5 to 8 nm in thickness.

The plasma membrane is a flexible and lipid bilayer that surrounds and contains the cytoplasm of the cell. Based on their arrangement of molecules and the presence of certain specialized components, it is also described as the fluid mosaic model.

The fluid mosaic model was first proposed in the year 1972 by American biologist Garth L. Nicolson and Seymour Jonathan Singer. The fluid mosaic model describes in detail about the plasma membrane structure in the eukaryotic cells, how well it is arranged along with their components – phospholipids, proteins, carbohydrates and cholesterol. These components give a fluid appearance to the plasma membrane.
Plasma Membrane Structure

Explore more: The fluid mosaic model

Functions of the Plasma Membrane

  • The plasma membrane functions as a physical barrier between the external environment and the inner cell organelles.
  • The plasma membrane is a selectively permeable membrane, which permits the movement of only certain molecules both in and out of the cell.
  • The plasma membranes play an important role in both the endocytosis and exocytosis process.
  • The plasma membrane also functions by facilitating the communication and signalling between the cells.
  • The plasma membrane plays a vital role in anchoring the cytoskeleton to provide shape to the cell and also maintains the cell potential.

Facts about Plasma Membrane

Both cell membrane and plasma membrane are often confused because of the similarity in words. But these two are the protective organelles of the cell and are very much different in their structure, composition and functions. The cell membrane is a type of plasma membrane and is not always the outermost layer of the cell.

For more information refer: Difference Between Cell Membrane and Plasma Membrane

This article concludes an introduction to plasma membranes, their facts and importance. To know more about plasma membranes, their structure, functions, other related topics and important questions, keep visiting our website at BYJU’S Biology.

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