Ultra-structure and functions of plasma membrane.pptx

Ultra-structure and functions of plasma membrane.

1. Ultra-structure and functions of plasma membrane Dhole N. A. Department of Botany, Digambarrao Bindu ACS College, Bhokar

2. Introduction The currently accepted model for the structure of the plasma membrane, called the fluid mosaic model , was first proposed in 1972. This model has evolved over time, but it still provides a good basic description of the structure and behavior of membranes in many cells. According to the fluid mosaic model, the plasma membrane is a mosaic of components—primarily, phospholipids, cholesterol, and proteins—that move freely and fluidly in the plane of the membrane. In other words, a diagram of the membrane (like the one below) is just a snapshot of a dynamic process in which phospholipids and proteins are continually sliding past one another. Interestingly enough, this fluidity means that if you insert a very fine needle into a cell, the membrane will simply part to flow around the needle; once the needle is removed, the membrane will flow back together seamlessly.

3. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/05%3A_Structure_and_Function_of_Plasma_Membranes/5.01%3A_Components_and_Structure_-_Components_of_Plasma_Membranes

4. Structure of Plasma Membranes: The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is a biological membrane that separates the interior of a cell from its outside environment. The primary function of the plasma membrane is to protect the cell from its surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells. Plasma membranes must be very flexible in order to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries. The plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix and other cells to help group cells together to form tissues. The membrane also maintains the cell potential.

5. The Plasma Membrane of a cell is composed of a Lipid Bilayer with Proteins embedded in it. The hydrophobic region of the lipid bilayer core excludes water, whereas the Hydrophilic regions both inside and outside of the cell allow water to be drawn into the structure through osmosis. In addition, there are various types of Protein structures associated with the Membrane, including integral Proteins, which are completely embedded in the lipid bilayer, and peripheral Proteins, which attach to the Membrane through their terminus region.

6. Lipid Bilayers: The cell's Plasma Membrane is composed primarily of lipids arranged into a lipid bilayer structure. Cholesterol is one component that contributes towards increasing the fluidity of the Membrane, as well as preventing the formation of lipid rafts which can compartmentalize the cell and restrict communication between different parts of the Membrane. The lipid bilayer is a highly stable structure that is resistant to changes in pH or temperature.

7. Proteins: The Proteins embedded in the Plasma Membrane play a variety of roles in the cell, including providing structural support for the Membrane to form a three-dimensional shape. In eukaryotic cells, Proteins are also involved in cellular signalling cascades involving hormones and neurotransmitters, which affect other molecules associated with the lipid bilayer structure.

8. Peripheral Proteins: The peripheral Proteins are attached to the lipid bilayer through their terminus region and can be found on the outside or inside of the cell. They play a variety of roles in the cell, including acting as receptors for signaling molecules, transporting ions or molecules across the Membrane, and participating in Protein-Protein interactions.

9. Integral Proteins: The integral Proteins are completely embedded in the lipid bilayer structure and are generally classified into two categories: alpha-helical or beta-barrel structures. The integral Proteins can be composed of either hydrophobic amino acids, which allows them to reside in the lipid bilayer core structure, or can contain both hydrophobic and hydrophilic regions in order to allow insertion into the Membrane. It is important to note that the Proteins embedded in the Plasma Membrane are not static and can move around within the lipid bilayer in a process known as lateral diffusion.

10. Components of Plasma Membrane When asked what is the composition of the Plasma Membrane the composition can be divided into lipids and Proteins. The main constituents that form the composition of the Plasma Membrane are: Phospholipids   This forms the chemical composition of the Plasma Membrane. These are lipid molecules with the phosphorus head groups forming the main fabric of the Membrane Peripheral Proteins   They occur on the outer or inner surface of the phospholipid bilayer, not in the middle

11. Cholesterol  The hydrophobic tails of the phospholipid bilayer consist of these molecules. Carbohydrates  Usually found on the outside of the Membrane, which also forms glycoProteins and glycolipids Integral Proteins  They are embedded inside or in-between the bilipid layer. 

12. Functions of the Plasma Membrane: The Proteins that are embedded in the Membrane perform specialized functions such as cell-cell recognition and the transport of molecules selectively.  It provides protection to the cell along with a fixed environment in the interior of the cell. It is responsible for performing different functions.  In the case of white and red blood cells, it is flexible as it aids in the movement through the blood capillaries. In addition, it also holds the cytoskeletal structure that provides shape to a cell and associates with the extracellular matrix and other cells to form a tissue.  The Plasma Membrane is the primarily responsible component for interacting with adjacent cells.  The Membrane also helps the Proteins to monitor and maintain the chemical climate inside the cell and also provides aids in shifting the molecules in the Membrane.

13. References: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/05%3A_Structure_and_Function_of_Plasma_Membranes/5.01%3A_Components_and_Structure_-_Components_of_Plasma_Membranes https://www.vedantu.com/neet/plasma-membrane-structure https://microbenotes.com/cell-plasma-membrane-structure-composition-functions/

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