3- Cell membrane and transport-2017-2018.pdf

Females & Males Slides Only Found in Males’ slides PHYSIOLOGY Only Found in Females’ slides Vary Important Notes Notes Extra Information Transport of Substances Through the Cell Membrane  Ob...

Females & Males Slides Only Found in Males’ slides PHYSIOLOGY Only Found in Females’ slides Vary Important Notes Notes Extra Information Transport of Substances Through the Cell Membrane  Objectives 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. Differentiate between passive and active transport mechanisms and give examples on each. Describe the different forms of passive transport and state the differences between them and the molecules transported by each. Describe the different forms of active transport and state the difference between primary and secondary types giving examples for each in the human body. Identify and describe carried‐mediated transport processes: Primary active transport, secondary active transport, facilitated, diffusion. Study source for this lecture: (Guyton & Hall Textbook of Medical Physiology, 13th ed, Chapter 4)  Eukaryotic Cell Structure The cell is basic unit of structure and function within the body (~100 trillion cells in body). Comprises three principal parts: i) Plasma (cell membrane) ii) Cytoplasm & organelles iii) Nucleus  Structure of the Cell Membrane It is a fluid and It covers the cell. not solid. Cell membrane = Thickness = 7.5-10 nm. plasma membrane ‫ما يفرق‬7-10 nm ‫عند األوالد مكتوب‬ = a lipid bilayer. Composition ‫احتمال اسئله عن النسب‬  The Plasma Membrane Main constituents of plasma membrane are phospholipids. Because it covers the inner and outer sides of cell membrane A phospholipid molecule have two ends: Hydrophilic (phosphate end) Hydrophobic (fatty acid end) Glycerol Heads (hydrophilic) facing ICF and ECF Tow fatty acid tails (hydrophobic).. ‫الرسمة بساليدات األوالد‬ face each other in the interior of the bilayer (Amphipathic)  Structure of the Cell Membrane Membrane proteins Integral Peripheral Span the thickness Are attached to one proteins (carrier) can participate in intracellular of the cell membrane surface of the signalling, present in one side, work as cell membrane receptor and cell surface antigens. Function as: membrane. 1. Channels (or pores). Function as: -The % of proteins is higher than phospholipids because proteins 2. Carrier proteins 1. Enzymes. are condensed 3. Receptors. 2. Adhesion molecules. (Guyton ad Hall Textbook of Physiology. 13th ed. Chapter-2)  Channel vs. Carrier Proteins Channel proteins Carrier proteins selectively form open pores bind the small molecule to be through which transported and then undergo molecules of the a conformational change to appropriate size release the molecule on the (e.g., ions) can cross other side of the membrane. the membrane. * They are small that’s why they pass  Structure of the Cell Membrane Function of CHOs (carbohydrates) : Receptors.. Cell-to-cell interaction. Immune reactions. Give most of cells overall –ve surface. Carbohydrates (CHOs) in the cell membrane are invariably attached to: – Proteins → Glycoproteins (most of it) carbohydrates + proteins – Lipids → Glycolipids (1/10) carbohydrates + lipids Proteoglycans (mainly carbohydrate substance bound together by protein) Carbohydrate molecules protrude to the outside of the cell forming a loose carbohydrate coat = “glycocalyx”  Cholesterol present in membranes in varying amounts controls much of the fluidity of the membrane function increases membrane FLEXIBILITY and STABILITY (-) (-) (-) (-) (-) (-) (-) 10 The Fluid Mosaic Model of Plasma Membrane ‫الرسمة بساليدات البنات‬  Transport through the cell membrane The membrane The cell membrane allows some is “selectively substances to cross permeable”… it but not others. It controls the type It arises from the & amount of membrane’s substances entering structure. and leaving the cell. Through the proteins. - water –soluble substances e.g. ions, glucose Directly through the lipid bilayer. - fat – soluble substance (O2, CO2, alcohol) ‫لد‬ ‫الرسمة بساليدات األو ا‬ -‫– معلومات مكرره‬  Substances that can Across the Cell Membrane Lipid soluble Water soluble substances substances Alternative route Oil and water do not mix Cross freely by Through membrane ‫الرسمة بساليدات البنات‬ diffusion proteins Substances That Can Move Across the Cell Membrane ‫الرسمات بساليدات البنات‬ Will enter the cell through a trans-membrane protein carrier/transporter/channel  Transport Mechanisms For cell viability, nutrients must continually enter the cell and waste products must exit. The transport of material between body or cellular compartments can be divided into: Passive Transport Active Transport Molecules move along Molecules move against their energy gradient. their energy gradient. Does not require Requires energy. energy. Types: Types: – Primary Active Transport. – Simple Diffusion. – Secondary Active Transport. -Facilitated Diffusion. – Osmosis. Bulk (Vesicular) Transport Large quantity transport of molecules  Passive Transport Mechanisms Simple Osmosis Diffusion Movement of from an water area of low to an area of high solute Facilitated concentration. Explanation: Passive transport is the movement from high to low concentrations, so why in osmosis shows the opposite? First, we have to know that there is a semipermeable membrane that is trying to prevent- some of the solutes pass to the other side. Therefore, the water has the priority to move from a place which contains (high volume of water-low solute concentration) to a place contains (low volume of water-high solute concentration).  Diffusion High conc. Diffusion = the substances will move random movement of substances down an energy gradient. Gradient Low conc. This gradient can be: – Concentration gr. – Electrical gr. Diffusion – Pressure gr.  Simple Diffusion The movement of molecules through the intermolecular spaces or membrane openings(channels) without the necessity of binding to a carrier protein on the membrane Small, uncharged substances cross the membrane by simple diffusion (by dissolving in PM). e.g. gases, alcohol, steroids and general anaesthetics Needs channels aqua porins (protein channels) ‫الرسمة بساليدات األولد‬ - Non carrier mediated transport down an electrochemical gradient 18  Factors affecting rate of diffusion 2‐ The number and 3‐ Chemical sizes of opening in 1‐ Amount of concentration the membrane for the difference substance available substance (selective Net Diffusion= P x A (C2 – C1 ) gating system) 4‐ Electrical potential 5‐ Molecular size of 6‐ Lipid solubility difference the substance 7‐ Temperature ‫ساليد كاملة من األوالد‬ ‫مها السجا تقول هذي وحقت البنات )الساليد اللي بعدها(زي بعض‬. ‫د‬ ‫‪Factors affecting rate of diffusion‬‬ ‫ساليد كاملة من البنات‬ ‫د ‪.‬مها السجا تقول هذي وحقت األوالد )الساليد اللي قبلها(زي بعض‬  Facilitated diffusion Down con. No ATP Question: How do larger and / or lipid-insoluble substances (charged molecules, ions) cross the lipid bilayer? The transported molecule binds to a carrier protein which then undergoes a conformational change allowing the molecule to pass through to the other side of the cell membrane. The carrier facilitates passage of the molecule through the CM They require transport (carrier) proteins - these are all INTEGRAL (TRANSMEMBRANE) PROTEINS Allow larger and / or lipid-insoluble substances (charged molecules, ions) cross the lipid bilayer Responsible for allowing transport of the majority of molecules (and all ions) across bio membranes (in & out). Rate of diffusion far higher than simple diffusion. Diffusion continues until equilibrium is reached Processes are SPECIFIC, SATURABLE and COMPETITIVE ‫الرسمة بساليدات األولد‬ General Steps for Facilitated Diffusion (Or any carrier-mediated transport) 3. Release 1. Solute- of solute binding on the step opposite side of the membrane 2. Change in carrier conformation allowing solute to pass through  There are two principal types of membrane proteins that mediate facilitated diffusion: GATED CHANNELS (are usually closed. They open in response to chemical , mechanical , electrical signals) 1) Channel Proteins Ion channels (e.g., Na+, K+, Cl- & Ca2+) OPEN CHANNELS ( create a water-filled pore) Aquaporins (water & small solutes) (106 – 108 ions/s) 2) Carrier Proteins UNIPORTERS Glucose & amino acids (never form an open channel between two sides of the membrane) Don’t get confused. Water can be both =) (102 – 5 x104 molecules/s) ‫هذه الساليد كاملة من األوالد‬: ‫مالحظة‬  The difference between simple and facilitated diffusion? ‫ساليد كاملة من البنات‬: ‫مالحظة‬ Simple diffusion Facilitated diffusion 1. Lipid-soluble substances 1. Also called “Carrier-mediated diffusion”. (e.g. O2,CO2, and alcohol)→ 2. Diffusion of a substance is “facilitated” by Pass through the interstices of the the use of a specific carrier protein. lipid bilayer. Water-soluble substances.2 3. Examples (glucose, amino acids). 4. The rate of diffusion increases (water, ions) → pass through channels.3 proportionately with the concentration of the that penetrate all the way through the CM diffusing substance until it reaches a transport maximum (Tmax). The rate of diffusion increases - At Tmax, an increase in the concentration of proportionately with the concentration of - the diffusing substance does not increase the the diffusing substance. rate of diffusion.  carrier protein ‫لما يوصل‬ binding site ‫لمرحلة أن كل‬ ‫مشغولة معناه وصل لمرحلة تركيز‬ ‫عالي ووصل مرحلة التشبع وهاذي‬ ‫فماراح يتغير‬Tm ‫النقطة اسمها‬ ‫بعد كذا‬rate Tm = transport maximum = the transport rate at which saturation occurs. The rate at which molecules can be transported by facilitated diffusion Depend on: 1-the number of solute-binding sites on the carrier. 2- the rate at which the carrier protein molecule can undergo conformational change back and forth between its bound and unbound state. ‫ساليد كاملة من البنات‬: ‫مالحظة‬  osmosis Because water molecules do not carry a charge, they can pass through the plasma membrane slowly. Because this is the diffusion of solute instead of solvent, it is unique. Aided by channels in membrane called aquaporin in some tissues -Water is the solute so water diffuses to more concentrated parts ‫هذه الساليد كاملة من األوالد‬: ‫مالحظة‬  Active transport Occurs when a cell membrane moves molecules or ions “uphill” against a concentration gradient (or an electrical or pressure gradient). It requires energy and a carrier protein. Examples: Ions like: sodium, potassium, calcium, iron, iodine, hydrogen ions Amino acids, glucose and other sugars. According to the source of energy used to fuel transport, it can be divided into: active Transport Indirect Primary Secondary source of Active ActiveTransport energy Direct source of energy Transport Co-transport Counter-transport  Types of Active Transport Primary Active Secondary Active The energy is derived The energy is derived directly from breakdown of adenosine indirectly by using the triphosphate (ATP) or concentration or some other high-energy electrochemical gradient phosphate compound. generated by a primary 3 main examples: active transporter. Sodium-potassium ATPase pump. Calcium ATPase pump Hydrogen ATPase pump.  Na+ / K+ ATPase ▪ Na+ / K+ ATPases most prevalent example of primary active transporters (vital for cell volume maintenance & neuronal cellular excitability). ▪ This pump functions by moving 3 molecules of sodium OUT and 2 molecules of potassium INTO the cell both against their concentration gradients. (‘electrogenic pump’.) ▪ Na‐K pump act as Carrier protein and binding site for Na inside the cell also binding site for K outside the cell ▪ In some cells (e.g., neuronesll.) (energy needed to move these ions uses 70% of all ATP production of the cell) Importance: 1. Maintaining Na and K concentration differences. 2. It’s the basis for nerve signal transmission. 3. Establishes a negative electrical voltage inside the cell. (–Ve)  H+-ATPase Pump Present in: Parietal cells of stomach → secretion of HCl in the stomach. Intercalated cells of distal renal tubules → excretion of acids from the body. Pumps H+ out of the cell and into the lumen. kidneys H+‐K ATPase inhibitors (treat ulcer disease). (omeprazol)  Ca+2 ATPase Pump Present in: – Sarcoplasmic reticulum in muscle cells – Mitochondria – Some cell membranes. Function: Maintains low Ca+2 concentration inside the cell.  Secondary Active Transport Transport of one or more solutes against an electrochemical gradient, coupled to the transport of another solute down an electrochemical gradient ‘’downhill’’ solute which is Na.(usually Na is the downhill solute) Energy is supplied indirectly form primary transport PCT = proximal convoluted tubules in the kidney co-transport (symporter) counter transport (anti-porter) All solutes move in the same direction When one substance is transported in the ’inside cell’’ (transported together and in the opposite direction to the other substance. same direction) Examples: Examples: – Na ‐ glucose Co transporter (PCT). – Na – amino acid Co transporter (PCT) – Na+-H+ counter-transporter (PCT) exchanger in the kidney – Na+-Ca+2 counter-transporter (present in many cell membrane) The Na+ / glucose symporter (Secondary Active co-transport ) Revision  Quiz 1.The cell membrane is composed of? a)Lipids, proteins, carbohydrates b)Proteins, ribosomes, carbohydrates c)Lipids, carbohydrates, enzymes, proteins d)Phosphate end, carbohydrates, integral protein Ans: a 2.Carrier proteins.... a)Carrier proteins are open pores through which molecules such as ions can cross the membrane b)Carrier proteins selectively bind to a small molecule and undergo a conformational change to release the molecule on the other side of the membrane c)are attached to one surface of the membrane d)function as enzymes and adhesion molecules Ans: b 3.What are examples of the two types of secondary active transport? Ans: Na ‐ glucose (co-transport) and Na+ -Ca+2 counter-transporter (counter transport)  Quiz 4.What is the difference between primary active transport and secondary active transport? Ans: Primary active transport uses direct energy source while secondary active transport uses indirect energy source 5.All of the following are factors that affect the rate of diffusion except… a)temperature b)surface area c)the number of organelles inside the cell d)electrical difference Ans: c  ‫‪Thank you & good luck‬‬ ‫‪Boys team members:‬‬ ‫‪Girls team members:‬‬ ‫▶‬ ‫هشام الشايع‬ ‫مها العمري‬ ‫▶‬ ‫هديل عورتاني‬ ‫سعود االحمري‬ ‫▶‬ ‫ريما العنزي‬ ‫▶‬ ‫عبدالرحمن آل الشيخ‬ ‫روتانا خطيب‬ ‫▶‬ ‫فايز الدرسوني‬ ‫لجين عزيز الرحمن‬ ‫▶‬ ‫محمد الحسن‬ ‫العنود المفرج‬ ‫▶‬ ‫ريم القرني‬ ‫محمد الصويغ‬ ‫▶‬ ‫عهد القرين‬ ‫▶‬ ‫محمد المنجومي‬ ‫العنود المنصور‬ ‫▶‬ ‫معاذ الحمود‬ ‫مها النهدي‬ ‫▶‬ ‫منصور العبرة‬ ‫بلقيس الراجحي‬ ‫▶‬ ‫احمد الصبي‬ ‫سارة البليهد‬ ‫▶‬ ‫ميعاد النفيعي‬ ‫▶‬ ‫خالد العقيلي‬ ‫نورة البسام‬ ‫▶‬ ‫عبدالجبار اليماني‬ ‫عبير العبدالجبار‬ ‫▶‬ ‫عمر الفوزان‬ ‫وجدان الشامري‬ ‫▶‬ ‫الجوهرة الشنيفي‬ ‫▶‬ ‫‪Team Leaders:‬‬ ‫‪-‬طارق العميم‬ ‫‪-‬مها بركة‬