Cell Membrane PowerPoint Presentation PDF

‫غشاء الخلية‬Cell membrane ‫شوائب الخلية‬Inclusions ‫عضيات‬Organelles ‫هيكل الخلية‬Cytoskeleton Cell membrane=Plasma membrane LM EM Functions  LM It can not be seen by light microscop...

‫غشاء الخلية‬Cell membrane ‫شوائب الخلية‬Inclusions ‫عضيات‬Organelles ‫هيكل الخلية‬Cytoskeleton Cell membrane=Plasma membrane LM EM Functions  LM It can not be seen by light microscope because it is too thin to be seen but the condensation of the stain on the outer surface of the cell membrane marks its.  EM A trilaminar structure, with an outer and an inner electron dense lines and a middle electron lucent zone in between.  Molecular structure of the cell membrane 3 components: 1-Lipid molecules: a- Phospholipids b- Cholesterol 2- Protein molecules. 3- Carbohydrate molecules. The cell membrane and almost all the membranes surrounding the membranous organelles have the same structure except for minor differences.  1- Lipid molecules ‫الدهون‬ A-Phospholipids Each phospholipid molecule consists of: 1- One polar ‫قطبى‬hydrophilic ‫محبة للماء‬head : faces the aqueous media on either side of the membrane. 2- Two long non-polar hydrophobic ‫كاره‬ ‫للماء‬tails (fatty acids): project towards the center of the membrane facing each other. They form weak non-covalent bonds with each other, holding the bilayer together. Why does the cell membrane appear as a trilaminar structure? Deposition of osmium in the hydrophilic heads Functions of phospholipid molecules  Functions of phospholipid molecules  Prevent passage of: Semipermeability of the membrane ‫شبه النفاذية‬/‫شبه المسامية‬ 1-Water soluble substances. 2- Polar ions.  Allow passages of: 1- Fat soluble substances. 2- Non polar substances.  B-Cholesterol They are incorporated within the lipid bilayer. Functions: 1- Stability of the membrane. 2-Regulation of membrane fluidity in body temperature.  2- Protein molecules Two types: A-Integral membrane proteins: They are embedded within the lipid bilayer. Most of these proteins traverse the whole thickness of the membrane and are called transmembrane proteins. Function: Allow passage of polar and water soluble substances.  B-Peripheral membrane proteins They are not embedded into lipid bilayer but they are loosely-associated with membrane. They are usually located on the cytoplasmic surface of the membrane. Function: form a link between the cell membrane and the cytoplasmic components.  3- Carbohydrate molecules They are present as glycoproteins and glycolipids of the cell membrane. They are oriented towards the outside of the membrane forming the cell coat.  Functions of cell coat 1- Cellular recognition e.g. the cell coat on the surface of red blood cells determines the four blood groups. 2- Cell-cell adhesion. 3- Receptor: for ligands by the glycoproteins of the cell membrane.  What is the function of the pointed structure? a. Controls membrane fluidity. b. Acts as a channel. c. Connects the cytoskeleton of the cell with the cell membrane. d. Cell to cell adhesion.  What is the function of the pointed structure? a. Controls membrane fluidity. b. Acts as a channel. c. Connects the cytoskeleton of the cell with the cell membrane. d. Cell to cell adhesion.