Plasma Membrane structure and normal functions
- 1. “IN THE NAME OF “ALLAH“SUBHANAHO-WA- TAALA WHO CREATED ME & THE WHOLE UNIVERSE” HAFIZ MUHAMMAD OWAIS 2011-AG-4268
- 3. The Cell Membrane – Gateway to the Cell
- 4. Cell Membrane Functions Maintain a high concentration of materials in the cell. Keep harmful materials out. Control the movement of materials into and out of the cell. Let the cell sense its environment.
- 5. CHEMICAL COMPOSITION & STRUCTURE • Chemically cell membrane composed of four components: • Phospholipids • Protein • Cholesterol • Carbohydrates (Glycocalyx)
- 6. Phospholipids Cholesterol Proteins (peripheral and integral) Carbohydrates Membrane Components
- 7. Cell membranes are like mosaics Cell membranes are like mosaics Lots of phospholipid tiles with protein, carbohydrate chain and cholesterol tiles thrown in!
- 8. Cell membranes are Cell membranes are phospholipid bilayers phospholipid bilayers
- 9. What are What are phospholipids phospholipids? ?
- 10. Phospholipids self assemble into Phospholipids self assemble into different structures because their different structures because their hydrophbic and hydrophilic ends hydrophbic and hydrophilic ends repel each other repel each other
- 11. What’s a Phospholipid Bilayer? What’s a Phospholipid Bilayer? 2 layers of phospholipids
- 12. • Each layer has: – a hydrophilic phosphate end (hydro = water, philic = loving) – and a hydrophobic lipid tail (phobic = fears, repels)
- 13. The Plasma Membrane is Semipermeable Small molecules and larger hydrophobic molecules move through. Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. The physical properties of phospholipids account for membrane assembly and many of its properties.
- 14. Lipid bilayer Small hydrophobic molecules: O2, CO2, N2, benzene Small uncharged polar molecules: H2O, ethanol, glycerol Larger uncharged polar molecules: glucose, amino acid, nucleotides SLECTIVE-PERMEABLITY of membrane depends on lipid bilayer molecule Ions: H+ , Na+ , HCO3 - , K+ , Ca+ , Mg2+ , CL- , etc. Transporters or channels
- 15. Cholesterol Cholesterol is a member of steroids or lipids and major component of animal plasma membrane.
- 16. Cholesterol stays in between fatty acids with its rigid planar steroid ring Phosphate Glycerol Fatty acid- (unsaturated) Hydrophobic fatty acid tails Polar Head Rigid Planar Steroid Ring Polar Head Non polar hydrocarbon Tail
- 17. cholesterol is a regulator of membrane fluidity. It makes bilayer less fluid (reduce fluidity), but it also prevent hydrocarbon chains come together to crystallize.
- 18. Proteins 1- Integral proteins: those proteins which are span the entire width of the membrane 2- Peripheral proteins : those proteins which are attached only on the surface of the membrane and do not penetrate all the way through membrane. Act as enzymes or controllers of transport of substances through membrane “pores”.
- 19. Types of Integral proteins 1. Carrier proteins • Those proteins which bond and drag molecules through the bilipid layer and release them on the opposite side of cell. 2. Channel proteins • In some cases the proteins simply act as a passive pore. Molecules will randomly move through it.
- 20. 3. Receptor proteins •These proteins are used in intercellular communication. • when a hormone binding to the receptor. This causes the receptor protein release a signal to perform some action. •E.g. glycoprotein acts as a receptor and recognition site
- 21. Marker proteins • Marker proteins extend across the cell membrane and serve to identify the cell.
- 22. Proteins Are Critical to Membrane Functions
- 23. Carbohydrates (glycocalyx) • The surface of the cell membrane is covered by a carbohydrate coat, known as the glycocalyx, •formed by the oligosaccharides of glycolipids and glycoproteins •. Glycocalyx protect the cell surface. •The oligosaccharides of the glycocalyx serve as markers for a variety of cell-cell interactions.
- 24. Transport process across the membrane • There are two types of transport across the membrane • Passive transport • Active transport
- 25. Passive Transport • Transport high to low concentration • “down hill movement • No energy require • Examples A. Diffusion, B. Osmosis, C. Facilitated diffusion
- 26. Three Forms of Passive Transport Across the Membrane osmosis Diffusion of water through a selectively permeable membrane is called “osmosis”
- 27. Three Forms of Transport Across the Membrane Example: Oxygen diffusing into a cell and carbon dioxide diffusing out.
- 28. Three Forms of Passive Transport Across the Membrane Examples: Glucose or amino acids moving from blood into a cell. An nerve electrical impulse results from opening protein channels for ions that move by facilitated diffusion.
- 29. osmosis Diffusion of water through a selectively permeable membrane is called “osmosis” In hypotonic environment Osmosis can kill cells
- 30. Active Transport •Transport form low to high concentration uphill” movement. •Require energy •Involves embedded proteins (transport proteins) acting like pumps Examples: sodium-potassium pump Bluk transport via (exocytosis .endocytosis)
- 31. Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Protein changes shape to move molecules: this requires energy!
- 32. Bulk transport across the plasma membranes also active transport occurs by two process •Endocytosis •Exocytosis Bulk (big particales) transport
- 33. Endocytosis • In endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane • There are three types of endocytosis 1. Phagocytosis (“cellular eating”) 2. Pinocytosis (“cellular drinking”) 3. Receptor-mediated endocytosis An Amoeba feeding via the process of endocytosis.
- 34. Solutes Pseudopodium “Food” or other particle Food vacuole CYTOPLASM Plasma membrane Vesicle Receptor Ligand Coat proteins Coated pit Coated vesicle EXTRACELLULAR FLUID Phagocytosis Pinocytosis Receptor-Mediated Endocytosis
- 35. Pinocytosis In pinocytosis, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles liquid material is transported through capillary cell by this way
- 36. Receptor-Mediated Endocytosis In receptor-mediated endocytosis, binding of molecule specificaly to receptors triggers vesicle formation. Receptor proteins make this a highly specific form of transport. Cholesterol is taken-up this way.
- 37. Phagocytosis In phagocytosis a cell engulfs a particle in a vacuole The vacuole fuses with a lysosome to digest the particle An Amoeba feeding via this process .
- 38. Exocytosis In exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents Many secretory cells use exocytosis to export their products
- 39. Exocytosis and Nervous System Function A nerve cell is also communicates to another cell by releasing chemicals via exocytosis at the synaptic terminal.
Editor's Notes
- #34: Figure 7.22 Exploring: Endocytosis in Animal Cells