Transport Methods 1 (PDF)

‫بسم هللا الرحمن الرحيم‬ ‫﴿و ما أوتيتم من العلم إال قليال﴾‬ ‫صدق هللا العظيم‬ ‫االسراء اية ‪85‬‬ ‫‪Dr.Hany borg‬‬ ‫‪1‬‬ Transport through cell membrane BY Dr /Hany M. borg Assistant professor of physiology KFS Univer...

‫بسم هللا الرحمن الرحيم‬ ‫﴿و ما أوتيتم من العلم إال قليال﴾‬ ‫صدق هللا العظيم‬ ‫االسراء اية ‪85‬‬ ‫‪Dr.Hany borg‬‬ ‫‪1‬‬ Transport through cell membrane BY Dr /Hany M. borg Assistant professor of physiology KFS University  ILOs 3 ❑Differentiate between simple diffusion, facilitated diffusion and osmosis. ❑Explain and give examples of simple diffusion, facilitated diffusion and osmosis. ❑Identify the different factors affecting the rate of diffusion Dr/ hany borg  What is Transport Across Cell Membrane? Transport across the cell membrane is a crucial process through which molecules present in our body get transported inside the cell, between cells, and excreted out of cells. which is essential for sustaining biological functions. It guarantees the flow of oxygen and nutrients while eliminating trash.  Transport through the Cell Membrane Transport Through Cell Membrane Active Vesicular Diffusion transport transport 6 Biophysics , Hany borg Diffusion 8 Diffusion of Liquids 9 What is diffusion?  Diffusion It is movement of substances across the cell membrane down its electrochemical gradient due to the continuous random thermal motion of its particles 11 Biophysics , Hany borg Diffusion Low concentration High concentration 12 Biophysics , hany borg  Diffusion It is divided into 3 subtypes: 1.Simple diffusion. 2.Facilitated diffusion. 3.Osmosis (water only) 13  Copy the chart into your notes Type of Transport Direction of Requires Classification of Transport protein movement Energy transport used from cell Simple Diffusion Facilitated Diffusion Active Transport  Simple Diffusion Def It is movement of substances across the cell membrane down its electrochemical gradient without extra energy & without the necessity of binding with carrier proteins 16  Simple Diffusion Characters: It is characterized by; a) Occurs down an electro-chemical gradient b) Passive i.e., no extra energy is required. 17 Biophysics , Hany borg  Simple Diffusion Characters: c) It is not rate-limiting i.e. linear with concentration gradients. d) The diffusion process is not saturable. 18 Biophysics , Abdelaziz Hussein Diffusion through Lipid bilayers 19 Biophysics , hany borg  b. Diffusion of water Water diffuses through lipid bilayer of the membrane at high rate like bullets due to; a. Small size. b. Very high kinetic energy 20 Biophysics Hany borg  Type of Transport Direction of Requires Classification Transport Protein movement Energy of Used from cell? transport Simple NO With NO PASSIVE WATER, Diffusion concentration CO2 & O2 gradient (high to low) Facilitated Diffusion Active Transport Facilitated Diffusion 22 Facilitated Diffusion Def It is the diffusion of substances across the cell membrane (down electrochemical gradient)i.e. without extra-energy with the aid of o special channel o or carrier protein. 23 particles will randomly move through the pores in Channel Proteins. copyright cmassengale 24  Diffusion through the Protein Channels Protein channels are watery pathways through the interstices of the protein molecules These channels are characterized by 1) Selective permeability (one key for one lock) 2) Gating of protein channels 25 Biophysics , hany borg  Selective Permeability of Protein Channels Most, but not all, protein channels are highly selective for the transport of one or more specific ions or molecules Selection by 1. size 2. Shape 3. Charge 26 Biophysics, hany borg Selective Permeability of Protein Channels 3. Nature of the electrical charges of its inside surfaces +ve charged channels for the passage of –ve charged particles. -ve charged channels for the passage of +ve charged particles Example: a. Na channels for Na b. K channels for K 27 Biophysics , hany borg  1. Leak Ion Channels Ion 28 1. Leak Ion Channels 29 1. Leak Ion Channels 30  1. Leak Ion Channels Always open i.e. no gate E.g., K channels Important in generation of resting membrane potential (see later) 31 2.Ligand-gated or chemical-gated ion channels Ion Ligand Gate Receptor 32 2.Ligand-gated or chemical-gated ion channels 33 2.Ligand-gated or chemical-gated ion channels 34 2.Ligand-gated or chemical-gated ion channels 35 2.Ligand-gated or chemical- gated ion channels 36 https://wiki.bio.purdue.edu/biol13100/images/8/8c/Muscle_pic_cropped!%2B.JPG 37  2.Ligand-gated or chemical- gated ion channels Channels open when chemical substance bind to its receptor E.g. K and Na channel at neuromuscular junction Important in generation of graded membrane potential (see later) 38 3. Voltage-gated ion channels Ion Gate 39 3.Voltage-gated ion channels ++++++++ _ _______ 40 3.Voltage-gated ion channels _ ________ +++++++++ 41 3. Voltage-gated ion channels _ _____ ++++++ 42  3. Voltage-gated ion channels Channels open by changes in cell membrane potential E.g., K and Na channels Important in generation of action potential (see later) 43 Facilitated Diffusion by carrier proteins 44 ✓ FACILITATED OR CARRIER- MEDIATED DIFFUSION is the type of diffusion by which the water-soluble substances having larger molecules are transported through the cell membrane with the help of a carrier protein. ✓ By this process, the substances are transported across the cell membrane faster than the transport by simple diffusion. ✓ Glucose and amino acids are transported by facilitated diffusion. Glucose or amino acid molecules cannot diffuse through the channels because the diameter of these molecules is larger than the diameter of the channels. ✓ Molecule of these substances binds with carrier protein. Now, some conformational change occurs in the carrier protein. Due to this change, the molecule reaches the other side of the cell membrane  Facilitated Diffusion Characters 1) It occurs down an electrochemical gradient 2) It is passive i.e. no energy is required. 3) It requires the presence of a transport carrier protein. 47 1)Structural specificity ( one key for one lock) 2)Saturable 3)Competition  Facilitated Diffusion Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. 49  Key Points A concentration gradient exists that would allow ions and polar molecules to diffuse into the cell, but these materials are repelled by the hydrophobic parts of the cell membrane. Facilitated diffusion uses integral membrane proteins to move polar or charged substances across the hydrophobic regions of the membrane. Channel proteins can aid in the facilitated diffusion of substances by forming a hydrophilic passage through the plasma membrane through which polar and charged substances can pass. Channel proteins can always be open, constantly allowing a particular substance into or out of the cell, depending on the concentration gradient; or they can be gated and can only be opened by a particular biological signal. Carrier proteins aid in facilitated diffusion by binding a particular substance, then altering their shape to bring that substance into or out of the cell.  Carrier Proteins Other carrier proteins change shape to move materials across the cell membrane 51 Type of Transport Direction of Requires Classification Transport Protein movement Energy of transport Used Simple NO With NO PASSIVE WATER, Diffusion concent. CO2, O2 gradient Facilitated Yes: With NO PASSIVE GLUCOSE Diffusion Carrier concent. Proteins gradient Active Transport  Coffee break 53 Dr/ hany borg  III-Osmosis ‘The diffusion of water across a membrane from an area of high concentration of water molecules to an area of low concentration of water across a partially permeable membrane.’ 54  Osmosis Water Solute 55  Osmosis Concentrated solution Diluted solution Cell membrane partially permeable. Sugar molecule Very low conc. of water molecules. Very high conc. of Inside cell Outside water molecules. cell 56  Cell membrane partially permeable. Low conc. of water OSMOSIS molecules. High conc. of Outside water molecules. Inside cell cell 57  Osmosis Cell membrane partially permeable. OSMO SIS Inside cell Outside cell EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water  Diffusion of H2O Across A Membrane High H2O potential Low H2O potential Low solute High solute 59 concentration  Aquaporins Water Channels Protein pores used during OSMOSIS WATER MOLECU LES 60  Water Channels (Aquaporins) Peter Agre 2003 Nobel Prize, Chemistry  Factors affecting the rate of diffusion 1-The concentration gradient (Concentration difference = Chemical gradient): The greater the difference between the two sides of the membrane the greater the rate of diffusion. Increase conc. gradient increase diffusion rate 2- The electrical gradient (difference): This factor particularly affects the rate of diffusion of ions. Increase electrical gradient increase diffusion rate. 3- The pressure difference : The greater the difference in pressure on both sides of the membrane the greater the rate of diffusion. Gases 63  Factors affecting the rate of 4- Temperature:- diffusion Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster. 5- The surface area:- The greater the surface area of the membrane the faster the diffusion rate. 6- The size and type of particles :- Large particles diffuse more slowly. Lipid soluble particles diffuse more rapidly. 7- Permeability of the membrane:- Increase Permeability increase the rate of diffusion. 8-Thickness of the membrane. ??? 64  Diffusion Fick’s Law of diffusion- M = Ds.A.C x Adolph Fick 1829-1901  Fick's law of diffusion The important to the cell (for a substance diffuse in both directions) is not the total substance diffusing in both directions but the difference between these two (net rate of diffusion in one direction). 66  Fick's law of diffusion Fick's law: D = diffusion coefficient. A = area of membrane (cm2). X = thickness of the membrane (cm). C in and C out = the concentration of the material on the inside and outside of the membrane, respectively (mmol/L or mmol/cm3). The -ve sign indicates that the material is moving down its concentration gradient 67 1. Which of the following is the primary driving force behind passive transport across cell membranes? A) ATP hydrolysis B) Concentration gradient C) Vesicle formation D) Membrane potential 1. Which of the following is the primary driving force behind passive transport across cell membranes? A) ATP hydrolysis B) Concentration gradient C) Vesicle formation D) Membrane potential 2.Facilitated diffusion differs from simple diffusion in that it requires: A) ATP B) Carrier or channel proteins C) Vesicles D) Calcium ions 2.Facilitated diffusion differs from simple diffusion in that it requires: A) ATP B) Carrier or channel proteins C) Vesicles D) Calcium ions 3. Which of the following molecules is least likely to diffuse directly through the lipid bilayer? A) Oxygen (O₂) B) Carbon dioxide (CO₂) C) Glucose D) Nitrogen (N₂) 3. Which of the following molecules is least likely to diffuse directly through the lipid bilayer? A) Oxygen (O₂) B) Carbon dioxide (CO₂) C) Glucose D) Nitrogen (N₂) 4.The process of osmosis moves water from: A) High solute concentration to low solute concentration B) Low water concentration to high water concentration C) High water concentration to low water concentration D) Low pressure to high pressure 4.The process of osmosis moves water from: A) High solute concentration to low solute concentration B) Low water concentration to high water concentration C) High water concentration to low water concentration D) Low pressure to high pressure 5. Which statement is TRUE about passive transport? A) It requires energy in the form of ATP. B) It always involves the use of carrier proteins. C) It moves substances down their concentration gradient. D) It is specific to ions only. 5. Which statement is TRUE about passive transport? A) It requires energy in the form of ATP. B) It always involves the use of carrier proteins. C) It moves substances down their concentration gradient. D) It is specific to ions only.