Cell Membrane Structure and Transport Across Cell Membrane PDF

Physiology Team 445 Cell membrane 2...

Physiology Team 445 Cell membrane 2 structure and transport across cell membrane EDITING FILE: OBJECTIVE - Main Text Describe the fluid mosaic model of membrane structure - Important and function Define permeability and list factors influencing permeability - Dr’s notes Identify and describe carried-mediated transport processes: Primary active transport, secondary active transport, facilities - Girls' Slides diffusion, simple diffusion, osmosis - Boys' Slides Differentiate between passive and active transport mechanisms and give examples on each. - Extra [email protected] File editing characteristics of cell membrane: -It covers the cell -Thin pliable and elastic 7-10nanometer -It is a fluid and not solid -Refer to as the Plasma membrane Composition of cell membrane 1- Protein 55% 2- Lipid 42% : Phospholipids 25%, cholesterol 13%, Glycolipid 4% 3- Carbohydrates 3% The Cell membrane phospholipids Consist of: 1- Glycerol head hydrophilic 2- Two fatty acid tails hydrophobic -Heads hydrophilic facing ICF and ECF , and tails hydrophobic face each other in the interior of the bilayer (It is called Amphipathic)  The cell membrane proteins integral proteins Peripheral proteins “ Carrier protein “ “ Carrier proteins” -span the whole thickness of the -Present in on side membrane -Hormone receptors -proteins provide structural channel -cell surface antigens or pores The cell membrane of carbohydrates Glycoproteins Glycolipids Proteoglycans Glycocalyx “ most of it “ mainly carbohydrates Carbohydrate molecules protrude to the outside of substance bound the cell forming a loose coat of carbohydrates. together by protein word ‘’glyco’ is part in the surface (hydrophilic) Function of carbohydrates: Attaches cell to each others Act as receptors substances “ help ligand to recognize its receptor “ Some enter in to immune reactions Give most of cells overall -ve surface Transport Through the cell Membrane: Cell membrane is selectively permeable. Through the proteins “ water” soluble substances e.g. ions , glucose. Directly through the lipid bilayer “ fat” soluble substances e.g. , O2, CO2 , OH.  Types of membrane transport: Diffusion Active transport Osmosis 1. Simple diffusion 1. Primary active transport 2. Facilitated diffusion 3. 2. Secondary active transport 3. What is the diffusion?: It is Random movement of substance either through the membrane directly or in combination with carrier protein down an electrochemical gradient. do not require input of energy=powered by concentration gradient or electrical gradient 1- Simple diffusion: Non Carrier mediated transport down an electrochemical gradient Diffusion of nonelectrolytes “ uncharged “ from high concentration to low concentration Diffusion of electrolytes “charged “ depend on both chemical as will as electrical potential difference  Rate of simple diffusion depend on: Amount of substance available The number of opening in the cell membrane for the substance “selective gating system” electrical potential difference molecular size of the substance lipid solubility Chemicals concentration difference net diffusion = P x A(C1-C2) P = permeability coefficient , “ temperature, solubility in lipids , size of molecule , Temperature thickness of membrane “ A = surface area C1-C2= gradient difference “ concentration difference , electrical difference, pressure difference “ 2- Facilitie diffusion it is a carrier mediated transport down an electrochemical gradient e.g glucose and amino acids Features of carrier mediated transport: 1-Saturation: increases concentration ——> increase binding of protein If all protein is occupied we achieve full saturation -the rate of diffusion reaches a maximum (Vmax) when all carriers are functioning as rapidly as possible 2-Stereospecificity: The binding site recognize a specific substance D-glucose but not L-glucose 3-Competition : Chemically similar substance can compete for the same binding site e.g. D-galactose and D-glucose Mechanism: Substance—> binding site —> substance protein—>complex —> conformational changes release of substance  Co-transport Counter transport Primary Secondary Active Transport Active Transport Active Transport It’s Transport (uphill) against electrochemical gradient Requirements Carrier Energy Protein Direct indirect Primary Secondary Active Transport Active Transport  Primary Active Transport Energy is supplied directly from ATP ATP ADP + P + energy Examples 1 2 3 Sodium - Potassium pump Calcium Hydrogen ions (Na + - K+ pump) (Ca²+ ATPase) (H + - K+ ATPase) Primary active of — it’s present in all cell membrane. 1 Sodium - Potassium pump (Na + - K + pump) — 3 Na+ in —2K + out out in Characteristic Function 1. Carrier protein is formed from α and 1. Maintaining Na+ and K+ Note β Subunits. concentration difference. the negative charge inside 2. Binding site for Na inside the cell. 2. It’s the basis of nerve signal the cell more 3. Binding site for K outside the cell. transmition. than outside 4. It has ATPase activity. 3. Maintaining negative potential 5. 3 Na out inside the cell. 6. 2 K in 4. Maintains a normal cell volume Discovery (in slides but considered as extra) -Na+/K+-ATPase pump was discovered by Jens Christian Skou in 1957. -In 1997, he received the Nobel Prize in Chemistry.  Primary active of Exists in: – Sarcoplasmic Reticulum (SR) 2 Calcium (Ca² + ATPase) – Mitochondria – In some cell membranes Function Maintaining a low Ca²+ concentration inside the cell Primary active of – Exists in: Stomach & Kidneys 3 Hydrogen ions (H + - K+ ATPase) – pump to the lumen ‫اخراج الهيدروجين‬ ‫يعمل على‬ ‫ وينتج‬،‫للخارج وادخال البوتاسيوم‬ ‫عند اخراج الهيدروجين ضخه في‬ ‫تجويف المعدة مما يسبب زيادة‬ ‫الهيدروجين وزيادة الحموضة‬ + + (H - K ATPase) inhibitors: ‫وبالتالي اإلصابة بقرحة المعدة‬ are used to treat ulcers e.g for an inhibitors (omeprazole) Secondary Active Transport Energy is supplied indirectly from Primary Active Transport — it’s transport of one or more solutes against an electrochemical gradient, coupled with the transport of another solute down an electrochemical gradient Types: 1 2 Co- transport Counter- transport (Co) means together (Counter) means against each other 1 Co- transport - All solutes move in the same direction ‘’ inside cell’’ - present in the intestinal tract & kidneys. e.g. Na+ - glucose Co-transport Na+ - amino acid Co-transport. -‘’downhill’’ solute is Na+ 2 Counter- transport ‫ واحد يطلع وواحد يدخل‬،‫باتجاهات مختلفة‬ - solutes move in against direction ‘’one inside ,one outside cell” Na+ is moving to the interior of the cell causing other substance to move out. ‫دخول الصوديوم داخل الخلية مع‬ ‫اتجاه التركيز وخروج مواد أخرى‬ ‫لخارج الخلية على عكس التركيز‬ e.g – Ca2+ - Na+ exchange. (present in many cell membranes of (muscle cell)) – Na+ - H + exchange in the kidney  Osmosis Net diffusion of water from a region of high water concentration to region of low water concentration Types 1 2 3 Hypertonic Solution Isotonic Solution Hypotonic Solution Net movement of water Equal movement of water Net movement of water out of cells into and out of cells into cells Osmotic equilibrium - Small changes in concentration of is maintained between intracellular solutes in the extracellular fluid can and extracellular fluids: cause tremendous change in cell volume. Intracellular osmolarity = extracellular osmolarity ≈ 285-300 mosm/L Hypertonic Isotonic Hypotonic same LESS SOLUTES outside MORE SOLUTES outside cell No change in cell cell volume LESS WATER IN CELL, MORE WATER IN CELL over time, cell loses water more solutes in cell. Isotonic solution: over time, cell gains water Hypertonic solution: - (not swell or shrink) Hypotonic solution: - (shrink) more than 0.9% - out is higher than in - 0.9% solution of sodium chloride or 5% glucose - (swelling) less than 0.9% - in is higher than out - same in and out  MCQs: 1- Which one is classified a hormone receptor:? A peripheral protein B integral protein C Osmosis D all of the above 2- What are the soluble substances through protein:? A O2 B CO2 C OH D glucose 3- Phospholipids are considered: A hydrophobic B Amphipathic C hydrophilic D none of them 4- H - K ATPase pump Can found in ? A Kidneys B Stomach C mitochondria D Both A&B 5- In Na/K-pump, the binding site for Na+ is......... the cell A doesn’t exist B between C outside D inside 6- All solutes move in the same direction ‘’ inside cell’’ A Osmosis B Co transport C Countertransport D Passive transport 7- Primary active transport of calcium functions in maintaining a high Ca2+ concentration inside the cell T True F False 7-F 6-B 5-D 4-D 3-B 2-D 1-A  MCQs: 8- Which of the following mechanisms of transport requires energy? A Simple diffusion B Active transport C Facilitated diffusion D Osmosis 9- The process that allows selective movement in and out of membrane? A Diffusion B Active transport C Simple diffusion D Facilitated diffusion 10- Which ONE of the following transporting mechanisms across cell membranes requires energy? Secondary active A B Simple diffusion C Facilitated diffusion D Osmosis transport 11- Simple diffusion and Facilitated diffusion share in which of the following characteristics? Transport solutes Require transport A Can be blocked B C against concentration D Does not require ATP proteins gradient 12- Lipids are ____ of the cell membrane A 3% B 9% C 55% D 42% 13- Which ONE of the following substances can diffuse across the cell membrane? A Oxygen B Calcium ion C Glucose D Amino acids 14- Co- transport means (against each other) T True F False 14-F 13-A 12-D 11-D 10-A 9-D 8-B Jood Alqosi Bandar Alqahtani Aljoharah Algazlan Abdulaziz Alowaid Dana Alanazi Naser Alnukhylan Maha alghamdi Khalid Alangari Rehad Almutairi Turki Alanazi Danah Alrabiah Rayan Alshahrani Rahaf Metlea Mohammed Almutairi Renad Bin Sanad Faris Aldawood Horia alotaibi Abdullah Alnami Latifah Al-Dossary Yazeed Alqarni Aryam Almotairi Ibrahim Almugrin Jory Alturki Abdulaziz Ibrahim Nada Almuhawwis Shahad alotaibi Basma Al-Bahkly Retaj Alosaimi