Cell Membrane PDF

Cell Membrane Cell Membrane ❏ What is a cell membrane and its characteristics? ❏ Functions of the Cell Membrane ❏ Structure of the Cell Membrane ❏ Chemical Composition ❏ Models of the Cell Membrane Cell Membrane: Characteristics Cell Membrane: Characteristics ❏ also known as plasma ❏ I...

Cell Membrane Cell Membrane ❏ What is a cell membrane and its characteristics? ❏ Functions of the Cell Membrane ❏ Structure of the Cell Membrane ❏ Chemical Composition ❏ Models of the Cell Membrane Cell Membrane: Characteristics Cell Membrane: Characteristics ❏ also known as plasma ❏ It has a lot of bead-like membrane is a biological structure attached or membrane which separates embedded in it. the interior of the cell from its exterior environment. ❏ It is semi-permeable (filters substance in and out of the ❏ looks literally like a cell). sandwich which has two layers facing each other ❏ The term is coined by C. Nageli and C. Cramer in 1855. Cell Membrane: Functions 1. Protection and Support ❏ keeps the cell intact ❏ maintains the cell’s shape and form ❏ acts as a barrier which covers and protects the cell from foreign substances Cell Membrane: Functions 2. Acts as a Receptor ❏ binding mechanism of the cell ❏ receives chemical signals from the external environment Cell Membrane: Functions 3. Transportation of Materials ❏ regulates the entrance and exit of different substances (gases, sugar, amino acids, ions, etc). ❏ acts as a medium in which the nutrients come in and wastes come out of the cell Cell Membrane: Structure Cell Membrane: Structure Cell Membrane: Chemical Composition The cell membrane is mainly consists of these three chemical components: 1.) LIPIDS - are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells. There are 4 classes of lipid present in the membrane namely: - Phospholipid - Glycolipids - Sphingolipids - Sterols Cell Membrane: Chemical Composition Phospholipids - are molecules that has a polar hydrophilic heads and nonpolar hydrophobic tails - This structure is critical to the permeability of the membrane. Cell Membrane: Chemical Composition Cholesterol - a type of lipid that prevents the fatty acid tails of the bilayer to stick to each other. - contributes to the fluidity of the cell membrane Cell Membrane: Chemical Composition 2.) PROTEINS - composed of amino acids made up of carbon, hydrogen oxygen, nitrogen and sulfur. This membrane is composed of 50% proteins like: - Structural proteins - Transport Proteins - Receptor Proteins - Enzymes Cell Membrane: Chemical Composition Cell Membrane: Chemical Composition Receptor Proteins - found on the surface of the cell membrane transmits messages to the cell’s exterior Cell Membrane: Chemical Composition Structural Proteins - found at the inner surface attached in the structural support providing the cell’s shape Cell Membrane: Chemical Composition Transport Proteins - embedded in the phospholipid bilayer which creates channels/tunnels that selectively allows the entrance and exit of substances Cell Membrane: Chemical Composition 3.) CARBOHYDRATES - are the sugar components of the membrane composed of carbon, hydrogen and oxygen. They are present in the exterior part or polar ends of phospholipids like: - Glycoproteins (attached to the external surface of the membrane which receive or transmit chemical signals) Cell Membrane: Models 1.) Davson-Danielli Model (1935) - known as the sandwich model - They studied triglyceride lipid bilayers over water surface and found out that they always arrange themselves with the polar heads facing outward. Cell Membrane: Models 1.) Fluid-Mosaic Model (1972) - Proposed by S. J. Singer and Garth Nicolson - Cell membrane can be considered as a two dimensional liquid where all lipids and proteins diffuse more or less freely. - the most widely accepted model SUMMARY ❏ Components include: ❏ Cell membrane is an organelle - Lipids (cholesterol, found in all types of cell which phospholipid) selectively allows the entrance - Proteins (structural, transport. and exit of substances in the receptor) cell. - Carbohydrates (glycoprotein) ❏ Functions include: - Protection and Support ❏ Models: - Receptors - Davson-Danielli Model (1935) - Transport of Materials - Fluid-Mosaic Model (1972) See you on our next synchronous meeting! Stay healthy! Stay alive!