Define ‘Plasma membrane’
A Cell and the organelles of a cell are surrounded by an outer membrane, this membrane is called a Plasma Membrane. It is a structure that separates cell content from the external environment and covers the whole cell.
Explain the presence of the plasma membrane in living cells.
A plasma membrane is a covering of cells that connects cells to their external environment. Both prokaryotic and Eukaryotic cells contain a plasma membrane. It is also called a phospholipid bilayer which is selectively permeable. It is a connecting system and a double membraned cell organelle. The plasma membrane is a boundary and selectively permeable in all living cells. It allows specific substances to enter and exit the cell. The movement of some materials also depends upon the plasma membrane.
What are the structure and functions of the plasma membrane?
The structure of the Plasma membrane is as follows:
- Plasma membrane is present in the cell and is also known as the cell membrane.
- Additionally, the plasma membrane is described by the fluid mosaic model which was proposed by American biologists Garth L. Nicolson and Seymour Jonathan Singer in 1972.
- It is a flexible lipid bilayer that covers the cytoplasm of the cell. Also, this membrane is made up of phospholipids, carbohydrates, conjugated molecules, and proteins which are 5 to 8 nm when it comes to its thickness.
- It does not allow water soluble molecules as well as ions to cross the membrane that’s why it is impermeable for specific materials.
- A lipid layer is semipermeable in the plasma membrane.
- The membrane proteins of the plasma membrane contain integral proteins.
The functions of the plasma membrane are as follows:
- The plasma membrane gives permission to the selective molecules to enter and exit the cell. Hence, this membrane is selectively permeable.
- In the processes like exocytosis and endocytosis, the plasma membrane performs some important functions.
- The potential of the cell is also maintained by the plasma membrane.
- In addition, it gives shape to the cell by anchoring the cytoskeleton and this is an important role in the plasma membrane.
- The plasma membrane separates the internal material of the cell from the external environment. In between the internal organelles of a cell and the external environment, it acts as a physical barrier. These are the functions of the plasma membrane.
Draw a neat diagram of ‘The fluid mosaic model’ and label it correctly.
Frequently Asked Questions
Which molecules are allowed by the plasma membrane?
The plasma membrane allows small polar molecules as well as hydrophobic molecules through the lipid layer. It is a selectively permeable membrane that does not take large polar molecules and ions through the membrane.
What is a plasma membrane composed of?
The plasma membrane of a cell is mainly composed of carbohydrates, phospholipid bilayer, and proteins. The composition of proteins and lipids changes depending on the different cells. The proteins may be integral or peripheral on the basis of location.
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