BIO U4:L1 - Cell Membrane Structure and Function PDF

Lesson 4.1 Structure and Functions of the Cell Membrane General Biology 11/2 Science, Technology, Engineering, and Mathematics What is your notion of cholesterol? 2 LDL cholesterol can clog the arterial walls. 3 Despite its harmful effects, cholest...

Lesson 4.1 Structure and Functions of the Cell Membrane General Biology 11/2 Science, Technology, Engineering, and Mathematics What is your notion of cholesterol? 2 LDL cholesterol can clog the arterial walls. 3 Despite its harmful effects, cholesterol is an important Cholesterol structural component of the plasma membrane of cells. 4 How are the structural components of the plasma membrane related to its functions? 5  Learning Competencies At the end of the lesson, you should be able to do the following: Describe the structural components of the cell membrane (STEM_BIO11/12-Ig-h-11). Relate the structure and composition of the cell membrane to its function (STEM_BIO 11/12-Ig-h-12). 6  Learning Objectives At the end of the lesson, you should be able to do the following: Identify the different structural components of the plasma membrane. Describe the diverse roles of proteins in the membrane. Compare membrane permeability for polar and nonpolar molecules. 7  Functions of the Plasma Membrane primary barrier of the cell General Functions of Cell Membrane receives allows the cell information or to move and stimulus grow 8 Structural Components of Plasma Membrane The cell membrane consists of a diversity of lipids, carbohydrates, and proteins. 9  Structural Components of Plasma Membrane Phospholipid Bilayer Molecules Embedded in the Membrane Membrane Proteins Carbohydrate Chains The aqueous nature of the intracellular and extracellular environments energetically favors the formation of the phospholipid bilayer. 10 How is the plasma membrane described by the fluid mosaic model? 11  Structural Components of Plasma Membrane Phospholipid Bilayer prevents the membrane from becoming too fluid at Molecules Embedded higher temperatures in the Membrane Membrane Proteins prevents the membrane from Cholesterol becoming too solid at lower temperatures Carbohydrate Chains 12  Structural Components of Plasma Membrane Phospholipid Bilayer It imparts flexibility to the membrane which is important for cells that Molecules Embedded particularly move. in the Membrane Importance of Fluidity Membrane Proteins The fluidity allows the synthesized membrane proteins and phospholipids to be easily incorporated Carbohydrate Chains into the membrane. 13  Structural Components of Plasma Membrane Phospholipid Bilayer Molecules Embedded in the Membrane Membrane Proteins Carbohydrate Chains The unicellular amoeba is capable of moving using its pseudopods or false feet because of the natural fluidity of the plasma membrane. 14  Structural Components of Plasma Membrane Phospholipid Bilayer Molecules Embedded in the Membrane Membrane Proteins The presence of double bonds in fatty acids helps Carbohydrate Chains maintain membrane fluidity. 15  Structural Components of Plasma Membrane Phospholipid Bilayer Saturated bonds (no double bond) will push Molecules Embedded against each other at in the Membrane low temperatures making the membrane more viscous and rigid. Membrane Proteins The presence of double bonds in fatty acids helps Carbohydrate Chains maintain membrane fluidity. 16  Structural Components of Plasma Membrane Phospholipid Bilayer The presence of kinks push adjacent phospholipids to Molecules Embedded maintain fluidity at low in the Membrane temperatures. Membrane Proteins The presence of double bonds in fatty acids helps Carbohydrate Chains maintain membrane fluidity. 17  Structural Components of Plasma Membrane Transport proteins may either be channel proteins Phospholipid Bilayer or carrier proteins. Molecules Embedded Transport in the Membrane Adhesion Membrane Proteins Recognition Carbohydrate Chains Receptor 18  Structural Components of Plasma Membrane Adhesion proteins fasten adjacent cells together in Phospholipid Bilayer animal tissues. Molecules Embedded Transport in the Membrane Adhesion Membrane Proteins Recognition Carbohydrate Chains Receptor 19  Structural Components of Plasma Membrane Recognition proteins help in recognition when the body is being invaded by Phospholipid Bilayer pathogens so that the necessary immune response may be triggered. Molecules Embedded Transport in the Membrane Adhesion Membrane Proteins Recognition Carbohydrate Chains Receptor 20  Structural Components of Plasma Membrane Receptor proteins have certain shapes that allow only specific Phospholipid Bilayer molecules to bind to them. Molecules Embedded Transport in the Membrane Adhesion Membrane Proteins Recognition Carbohydrate Chains Receptor 21  Structural Components of Plasma Membrane Phospholipid Bilayer Glycolipid Glycoprotein Carbohydrate (Carbohydrate + Lipid) (Carbohydrate + Protein) Carbohydrate Lipid Molecules Embedded Protein in the Membrane Membrane Proteins Carbohydrate Chains The carbohydrate chains occur only on the outside surface of the lipid bilayer or on the peripheral proteins. 22 How does the plasma membrane permit certain molecules to enter selectively into the cell? 23  Permeability of the Cell Membrane Selectively permeable polar and larger molecules small, non-charged molecules concentration gradient Small, uncharged particles trying to cross the plasma membrane 24 Permeability of the Cell Membrane Impermeable polar molecules large molecules amino nucleic glucose proteins acids acids Molecules that require energy expenditure for them to be transported across the membrane 25 Permeability of the Cell Membrane Permeable Lipids Alcohol small molecules carbon oxygen nitrogen dioxide water Molecules that are free to move across the membrane 26 What could be the effect on a cell if one tries to remove the cholesterol in its plasma membrane? 27  Check Your Understanding Identify the correct term being described in each item. 1. This term describes the membrane’s structure because of the diverse protein molecules suspended in a fluid of phospholipid bilayer. 2. These are phospholipid molecules with attached carbohydrate chains. 3. These are protein molecules on the cell surface with attached carbohydrate chains. 28  Check Your Understanding Determine the accuracy of each of the following statements. Write true if the statement is correct and false if otherwise. 1. The fluidity of the plasma membrane is attributed to the diversity of membrane proteins. 2. The carbohydrates attached to peripheral proteins contribute to cellular recognition. 3. Hormones or chemical messengers bind to adhesion proteins. 29  Let’s Sum It Up! The plasma membrane is described by the fluid mosaic model because its structure is composed of diverse protein molecules embedded in a mosaic-like fashion in the fluid phospholipid bilayer. 30  Let’s Sum It Up! The phospholipids with the attached carbohydrates chains are called glycolipids and proteins with carbohydrate chains are called glycoproteins which can be found on the outside surface of the cell. They usually function for cell-cell recognition. 31  Let’s Sum It Up! Diverse proteins are associated with the plasma membrane, and they are functionally classified into whether they transport molecules, aid in the recognition of other cells, or whether they determine the presence of substances in the extracellular environment. 32  Let’s Sum It Up! The phospholipid bilayer is selectively permeable because it only allows certain substances into cells while keeping others out. The size and the chemical nature of the molecules are important determiners of the permeability of the membrane to certain substances. 33  Let’s Sum It Up! The molecules that pass through the plasma membrane follow a concentration gradient wherein they move from an area of higher concentration to an area of lower concentration. 34 Let’s Sum It Up! The structural components and functions of the plasma membrane 35 Challenge Yourself Type 2 diabetes is the most common type of diabetes in which the cells of the body cannot recognize insulin, the hormone that lowers blood sugar level. Explain which proteins in the plasma membrane are most affected and why? 36  Photo Credits Bibliography Hoefnagels, Marielle. Biology: The Essentials. 2nd ed. McGraw-Hill Education, 2016. Mader, Sylvia S., and Michael Windelspecht. Biology. 11th ed. Slide 3: SAG Clogged-Artery-CS 160421 01, by McGraw-Hill Education, 2014. Scientific Animations, Girish Khera is licensed under CC BY SA-4.0 via Wikimedia Commons. Reece, Jane B, Martha R. Taylor, Eric J. Simon, Jean L. Dickey, Slide 22: OSC Microbio 03 04 EukPlasMem, by CNX and Kelly Hogan. Biology Concepts and Connections. OpenStax is licensed under CC BY 4.0 via Wikimedia Commons. 8th ed. Pearson Education South Asia Pte Ltd., 2016. Simon, Eric J., and Jane B. Reece. Campbell Essential Biology. 5th ed. Pearson Education Inc., 2013. Starr, Cecie, Christine A. Evers, and Lisa Starr. Biology Today and Tomorrow. 4th ed. Cengage Learning Asia Pte Ltd, 2014. 37