3-Cell-membrane-structure (1).pdf
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Physiology team 434 Contact us : [email protected] 434 Physiolog...
Physiology team 434 Contact us : [email protected] 434 Physiology team Cell Membrane Structure And Transport Across Cell Membrane :قال الشيخ ابن عثيمني رمحه اهلل: Important Extra القلب وعاء إذا امتأل بشيء مل يبق للشيء اآلخر حمل، explanation فإذا امتأل حبب الدنيا انشغل عن حب اهلل عز وجل ورسوله صلى اهلل عليه وسلم وصار اإلنسان ليس له هم Girls Boys .إال الكسب notes notes 366).ص 9 /ج /شرح بلوغ المرام ( Physiology team 434 Contact us : [email protected] 434 Physiology team At the end of this session, the students should be able to: Describe the fluid mosaic model of membrane structure and function Define permeability and list factors influencing permeability Identify and describe carried‐mediated transport processes: Primary active transport, secondary active transport, facilitated diffusion. Physiology team 434 Contact us : [email protected] 434 Physiology team Cell Membrane Structure Transport Passive Active Simple Primary Diffusion Facilitated Diffusion Secondary Osmosis Physiology team 434 Contact us : [email protected] 434 Physiology team General characteristics of Cell membrane: - Lipid bilayer (phospholipids) - Covers the cell. - It’s fluid not solid. - 7 - 10 nanometer thick. (thin) - Also referred to as plasma membrane. Cell membrane Composition Carbohydrates Protein 55% Lipids 42% 3% Physiology team 434 Contact us : [email protected] 434 Physiology team Phospholipids (Amphipathic) : ECF 1. Glycerol head (hydrophilic). 2. Two fatty acid ‘’tails’’ (hydrophobic) ICF - Heads (hydrophilic) facing ICF and ECF and tails (hydrophobic) face each other in the interior of the bilayer Physiology team 434 Contact us : [email protected] 434 Physiology team Proteins: 1-Integral proteins: - Span the membrane. - Proteins provide structural channels or pores. - Carrier proteins. 2-Peripheral protein: - Present in one side. - Hormone receptors. - Cell membrane antigens Physiology team 434 Contact us : [email protected] 434 Physiology team This an example of how protein works as a channel for ions : 1) by electric. 2) by ligand gated: (explanation) many ion channels open or close in response to binding a small signaling molecule or "ligand" مثل المفتاح. Physiology team 434 Contact us : [email protected] 434 Physiology team Carbohydrate : 1-Glycoproteins (Most of integral proteins are glycoproteins). 2-Glycolipids (Represent 1/10 of the membrane lipids) 3-Proteoglycans (mainly carbohydrate substance bound together by protein) 4-Glycocalyx (the entire outside surface of the cell often has a loose carbohydrate coat called the glycocalyx) Physiology team 434 Contact us : [email protected] 434 Physiology team ‘’ glyco ’’ part is in the surface forming. The “glyco” portions of these molecules (glycoproteins & glycolipids) almost invariably protrude to the outside of the cell, dangling outward from the cell surface أي أن الكربوهيدرات المرتبطة بالدهون والبروتينات تكون بارزة ومتدلية من سطح الخلية Physiology team 434 Contact us : [email protected] 434 Physiology team Functions of Carbohydrates Attaches cell to each other's. (by glycoclyx) Some enter in to immune reactions. Act as receptors substances (help ligand to recognize its receptor). Give most of cells overall –ve surface. (to replace other negative object) Physiology team 434 Contact us : [email protected] 434 Physiology team - Cell membrane is Selectively Permeable Through the proteins (Water -soluble substances e.g. ions, glucose) Through the lipid bilayer (Fat -soluble substance e.g. O2, CO2, N2, alcohol) جميع المواد تدخل للخاليا إما عن طريق البروتين او عن طريق طبقتي الدهون Physiology team 434 Contact us : [email protected] 434 Physiology team Types of membrane movement Active Transport Passive Transport ( Energy is (NO Energy required ) required ) Simple Primary Secondary Diffusion Facilitate Osmosis Active Active d Diffusion (no carrier) Transport Transport N.B: Simple diffusion is the only form of transport that is not carrier-mediated. Physiology team 434 Contact us : [email protected] 434 Physiology team Diffusion : Random movement of substance either through the membrane directly or in combination with carrier protein down an electrochemical gradient. Downhill transport (Simple diffusion & facilitated) don’t require input of energy(ATP). Instead, its powered by Concentration gradient or electrical gradient. Physiology team 434 Contact us : [email protected] 434 Physiology team Non-carrier mediated transport down an electrochemical gradient. Simple Diffusion Diffusion of nonelectrolytes (uncharged) from high concentration to low concentration. Diffusion of electrolytes (charged) depend on both chemical as will as electrical potential difference. Facilitated Carrier mediated transport down an electrochemical gradient. Physiology team 434 Contact us : [email protected] 434 Physiology team Amount of substance Increasing in diffusion due to available increasing in amount The number of Increasing in diffusion due to increasing opening pores in the in number of pores cell membrane the rate of net diffusion into the cell is proportional Chemical concentration to the concentration on the outside minus the difference net diffusion= P x A concentration on the inside CO = Concentration (CO-CI) Outside - CI = Concentration Inside Rate of Simple Electrical potential the electrical charges of the ions cause them to move difference. EPD=± 61 log through the membrane even though no concentration Diffusion C1/C2 difference exists to cause movement Molecular size of the Increasing in diffusion due to decreasing substance in molecular size Increasing in diffusion due to increasing in lipid Lipid solubility solubility Temperature Increasing in diffusion due to increasing in heat Physiology team 434 Contact us : [email protected] 434 Physiology team Chemical concentration Electrical potential difference. difference EPD=± 61 log C1/C2 net diffusion= P x A (CO-CI) Not that important Physiology team 434 Contact us : [email protected] 434 Physiology team Features Of Carrier Mediated Transport (Facilitated diffusion & Active transport) Stereo Saturation Competition specificity If all protein is The binding site Chemically similar occupied we recognize a specific substance can achieve full substance e.g. compete for the saturation same binding site. D-glucose but not L- glucose. Physiology team 434 Contact us : [email protected] 434 Physiology team Substance → binding site → substance protein complex → conformational changes → release of substance. Tm = Saturation Physiology team 434 Contact us : [email protected] 434 Physiology team Active Transport : Transport (uphill) → against electrochemical gradient. Required energy (Direct & Indirect) Active Transport Required carrier – protein. divided into two types according to the source of the energy used to cause the transport : Primary active Secondary transport Active transport (Directly) (Indirectly) Counter Co-Transport Transport Physiology team 434 Contact us : [email protected] 434 Physiology team Primary Active Transport : Energy is supplied directly from ATP. ATP → ADP +P+ energy. A. Sodium-Potassium pump (Na+-K+ pump): - Its present in all cell membranes. - 3 Na+ in → out. - 2 K+ out → in. Physiology team 434 Contact us : [email protected] 434 Physiology team CHARACTERISTICS OF THE FUNCTIONS OF THE PUMP ( Na+ - k+ PUMP ) A. Maintaining Na+ and K+ Carrier protein. concentration difference. Binding site for Na inside the B. Maintaining –ve potential cell. inside Binding site for K outside the the cell. cell. C. Maintains a normal cell It has ATPase activity. volume. 3 Na out. D. It’s the basis of nerve signal 2 K in. transmition. Physiology team 434 Contact us : [email protected] 434 Physiology team B. primary active transport of calcium (Ca²+ ATPase): o Site: - Sarcoplasmic reticulum (SR). - Mitochondria. - in some cell membranes. o Function: Maintaining a low Ca²+ concentration inside the cell. C. primary active transport of hydrogen ions H+-K+ ATPase: o Site: - Stomach. H تمنع خروج - Kidneys. وبالتالي تعالج o Function: القرحة. - pump to the lumen. - H+-K+ ATPase inhibitors (treat ulcer disease). (omeprazole) Physiology team 434 Contact us : [email protected] 434 Physiology team Secondary Active Transport: Co- transport OR Counter transport: is transport of one or more solutes against an electrochemical gradient, coupled to the transport of another solute down an electrochemical gradient. - ‘’ downhill ’’ solute is Na. - Energy is supplied indirectly form primary transport. Physiology team 434 Contact us : [email protected] 434 Physiology team Co-Transport Counter Transport - All solutes move in the same -Na+ is moving to the interior direction to ‘’inside the cell’’. causing other substance to move out. - Na+ - glucose Co-transport. - Na+ - amino acid Co- -Ca²+ - Na+ exchange. transport. -(Present in many cell - In the intestinal tract & kidney membranes) -Na+ - H+ exchange in the kidney Physiology team 434 Contact us : [email protected] 434 Physiology team What the difference? (Explanation Only) 1-In primary active transport, the energy is derived directly from breakdown of adenosine triphosphate (ATP) or of some other high-energy phosphate compound. 2-In secondary active transport, the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane, created originally by primary active transport. Physiology team 434 Contact us : [email protected] 434 Physiology team The cell membrane consists of protein, lipid and carbohydrates. The cell membrane is selectively permeable. The solutes can enter the cell either with protein or lipid. Types of membrane transport are: diffusion, active transport and osmosis. In diffusion there is no need for energy, but in active transport we need energy, because it is against the electrochemical gradient. Physiology team 434 Contact us : [email protected] 434 Physiology team 1- https://www.youtube.com/watch?v=kfy92hd aAH0 ACTIVE AND PASSIVE TRANSPORT 2- https://www.youtube.com/watch?v=awz6lIss 3hQ NA+K+ PUMP 3- http://bk.psu.edu/clt/bisc4/ipweb/systems/s ystems/fluids/index.html (it is important for the first 5 lectures) Physiology team 434 Contact us : [email protected] 434 Physiology team Q1: Which of the following statement is true about cell membrane? Q4: Which of the following act as A- It is a solid membrane receptor recognition B- It is 11 nanometer thick in cell membrane? C- It is hydrophilic A- Carbohydrates D- It is Amphipathic B- Proteins C- Lipids Q2: The Cell membrane phospholipids D- Both A and C consist of two fatty Acids which is “hydrophilic”. Q5: Simple Diffusion is a carrier A- True mediated transport B- False down its electrochemical gradient. A- True Q3: In “Sodium – Potassium pump” B- False which of these will happen? A- 2Na+ in & 2K+ out B- 2Na+ in & 3K+ out C- 3Na+ in & 2K+ out D- 3Na+ out & 2K+ in Physiology team 434 Contact us : [email protected] 434 Physiology team Q6: Which of the following is an example for secondary active transport? A- Na+ - Amino acid Co-transport B- Na+ - K+ pump C- Active transport of calcium (Ca2 + ATPase ) D- Active transport of hydrogen ions ( H+ - K ) 6-A 5-B 4-A 3-D 2-B 1-D ANSWERS: Malak Saud AL-Khathlan, Rawan Ghandor, Nouf Alharbi, Mona Almoteb, Razan Alsubhi.
