PowerPoint Presentation

[Audio] Biochemistry EBA1300 Lecture 3 Cellular transport Dr /Sherine Farouk.

[Audio] Cell membrane All cells are surrounded by a thin flexible barrier known as cell membrane Cell membranes are made of a double layer sheet called a lipid bilayer. Functions of the Cell Membrane: Cell membrane separates the components of a cell from its environment—surrounds the cell TEM picture of a real cell membrane. "Gatekeeper" of the cell—regulates the flow of materials into and out of cell—selectively permeable.

[Audio] Types of Cellular Transport Cellular transport is the process of molecules or material moving in and out of the cell Passive Transport cell doesn't use energy 1. Simple Diffusion 2. Facilitated Diffusion 3. Osmosis Active Transport cell does use energy 1. Protein Pumps 2. Endocytosis 3. Exocytosis.

[Audio] Diffusion Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration down the concentration gradient until an equilibrium is established due to random movement(collisions). Energy is not required زيكرتلا جردت.

[Audio] Passive transport يبلسلا لقنلا Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes. Properties: cell uses no energy molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration..

[Audio] Types of Passive Transport 1. Diffusion 2. Facilitated Diffusion – diffusion with the help of transport proteins 3. Osmosis – diffusion of water.

[Audio] Passive Transport 1-Simple diffusion Can only occur if the molecules moving in and out of the cell are: Small Uncharged (-non polar) meaning they contain no (+ or )charges e.g (CO2,O2) Lipophilic ( A substance is lipophilic if it is able to dissolve much more easily in lipid) Simple diffusion – movement of small or lipophilic molecules (e.g. O2, CO2, etc.) يسبلا راشتنلاا تازيممط Features of simple diffusion: Molecules move from an area of high concentration to an area of low concentration Diffusion continues until all molecules are evenly spaced (equilibrium نزاوتلا is reached) -Note: molecules will still move around but stay spread out. No energy is required(no ATP) No carriers are required No limit (no saturation).

[Audio] Passive Transport: 2. Facilitated Diffusion Facilitated diffusion is the passive movement of molecules across the cell membrane via the aid of a membrane transport proteins. Transport Proteins are specific – they "select" only certain molecules to cross the membrane It is utilised by molecules that are unable to freely cross the phospholipid bilayer (large, polar molecules and ions like ( Na or K) This process is mediated by two distinct types of transport proteins – channel proteins and carrier proteins.

[Audio] Facilitated Diffusion Features of facilitated diffusion: Molecules move from an area of high concentration to an area of low concentration No energy is required(no ATP) involves transport proteins Saturation(limited). Specificity Competition inhibition.

[Audio] Passive transport. Passive transport.

[Audio] Types of membrane transport proteins. Types of membrane transport proteins.

[Audio] Osmosis Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane Water diffuses across a membrane from an area of high concentration to an area of low concentration..

[Audio] Tonicity The tonicity of a solution usually refers to its solute concentration relative to that of another solution on the opposite side of a cell membrane Concentration describes the amount of solutes dissolved by a solution. What do the prefixes mean: a. hypo = low b. iso = equal c. hyper = high.

[Audio] Osmosis Animations for isotonic, hypertonic, Hypotonic Solution and hypotonic solutions Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!.

[Audio] Osmosis Animations for isotonic, hypertonic, Hypertonic Solution and hypotonic solutions Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!.

[Audio] Osmosis Animations for isotonic, hypertonic, and hypotonic Isotonic Solution solutions Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium).

[Audio] Animal Cell placed in different solution tonicity When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly burst..

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[Audio] Paramecium(protist)removingexcesswatervideoHowOrganismsDealwith OsmoticPressure Bacteriaandplantshavecellwallsthatpreventthemfromover-expanding.Inplantsthepressureexertedonthecellwalliscalledturgorpressure. Aprotistlikeparameciumhascontractilevacuolesthatcollectwaterflowinginandpumpitouttopreventthemfromoverexpanding. Animalcellsarebathedinblood.Kidneyskeepthebloodisotonicbyremoveexcesssaltandwater..

[Audio] Where are Contractile Vacuoles Found Contractile vacuoles are primarily found in freshwater protists, such as amoeba, paramecium, and euglena. They also occur in lower metazoans, such as sponges and hydras. Function: What does the Contractile Vacuole Do The contractile vacuole acts as a key regulator of cellular water flow, thus maintaining water balance in the cell. As we know, the tonicity or the concentration of solutions should remain the same in the intracellular and extracellular space for the proper functioning of the cell. So, whenever there is an imbalance in solution concentration, the cells undergo a specialized process called osmoregulation. Osmoregulation is the process of regulating a constant osmotic pressure of the cellular fluid by controlling the water flow and solute concentrations relative to the surrounding..

[Audio] Active transport Active transport is the movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration Active transport requires carrier proteins (each carrier protein (pumps) being specific for a particular type of molecule or ion. Dr/Sherine Farouk 21.

[Audio] Active transport Although facilitated diffusion also uses carrier proteins, active transport is different as it requires energy The energy is required to make the carrier protein change shape, allowing it to transfer the molecules or ions across the cell membrane The energy required is provided by ATP (adenosine triphosphate) produced during respiration. The ATP is hydrolysed to release energy There are two ways in which active transport occurs: Primary Active Transport Secondary Active Transport Dr/Sherine Farouk 22.

[Audio] Primary Active Transport Energy Source: Directly uses energy from ATP. Mechanism: Transports ions or molecules against their concentration gradient using a pump protein (e.g., sodium-potassium pump). Example: The sodium-potassium pump moves sodium ions out of the cell and potassium ions into the cell, using ATP to maintain the concentration gradients..

[Audio] sodium-potassium pump An example for primary active transport The sodium-potassium pump transports sodium out of the cell and potassium into the cell in a repeating cycle of conformational (shape) changes. In each cycle, three sodium ions exit the cell, while two potassium ions enter. helping to maintain an electrical gradient across cell membranes This process takes place in the following steps: 24 Dr/Sherine Farouk.

[Audio] 25 Dr/Sherine Farouk. 25 Dr/Sherine Farouk.

[Audio] Secondary Active Transport Energy Source: Does not directly use ATP; instead, it relies on the energy stored in the concentration gradient created by primary active transport. Mechanism: Utilizes the movement of one substance down its concentration gradient to drive the transport of another substance against its gradient. This can be further categorized into: Symport: Both substances move in the same direction. Antiport: Substances move in opposite directions. Example: The sodium-glucose transporter uses the sodium gradient (created by the sodium-potassium pump) to transport glucose into the cell along with sodium ions..

[Audio] Types of secondary active transport 1-symport 2-Antiport or Counter-transport or exchangers 27 Dr/Sherine Farouk.

[Audio] 1-Symport Symport: when two kinds of molecules move in the same direction while diffusing through carrier proteins Symport or "Co-transport" means that a molecule is allowed to be transported from high to low concentration region while moving another molecule with it from low to high concentration. It in fact is pulling the other molecule with it into the cell. 28 Dr/Sherine Farouk.

[Audio] Example for symport sodium glucose co-transporter On its exterior side the transport protein has 2 binding sites, one for sodium and one for glucose. When both of these bind to the protein there is a conformational change allowing the electrochemical gradient to provide the energy needed to transport both of these molecules into the cell. 29 Dr/Sherine Farouk.

[Audio] 2-Antiport or Counter-transport It is a type of active transport. means that 2 different molecules or ions are being transported through a membrane at the same time but in opposite directions. One of the species is allowed to flow from high concentration to a lower concentration (often Sodium) while the other species is transported simultaneously to the other side. An example of this system is the sodium-calcium antiporter or exchanger. This allows three sodium ions into the cells for the transport of one calcium ion. Dr/Sherine Farouk 30.

[Audio] Na+-Ca2+ counter-transport where Na+ binds to the transport carrier protein on its exterior side, and Ca2+ bound to the same protein on the membranes interior side. Once both are bound, a conformational change occurs the sodium ion is transported to the interior and calcium to the exterior. This transporter is situated on almost all cell membranes. 31 Dr/Sherine Farouk.

Bulk Transport When molecules are too large to move through a channel protein or by using a carrier protein, vesicles are used to move the "bulk" molecule. Bulk transport of substances is accomplished by I. endocytosis — movement of substances into the cell 2. exocytosis — movement of materials out of the cell BOTH require energy from the cell.

[Audio] Importanceofbulktransport Mostcellsdohavebulktransportmechanismsofsomekind. Thesemechanismsallowcellsto 1-obtainnutrientsfromtheenvironment, 2-selectively"capture"specificparticlesfromtheextracellularfluid, 3-orreleasesignalingmoleculestocommunicatewithneighborsDr/SherineFarouk 33.

[Audio] types of bulk transport Rceptor mediated endocytosis 34 Dr/Sherine Farouk.

EXOCYTOSIS • Occurs when materials discharge from the cell • Vesicle in the cytoplasm fuse with the cell membrane and release their content to the exterior of the cell • Used in animals to secrete hormones, neurotransmitters, digestive enzymes etc. Fig: Exocytosis EXOCYTOSIS Secretory granule.

[Audio] Endocytosis Thecarrierandchannelproteinsdiscussedintheprecedingsectiontransportsmallmoleculesthroughthephospholipidbilayer. Eukaryoticcellsarealsoabletotakeupmacromoleculesandparticlesfromthesurroundingmediumbyadistinctprocesscalledendocytosis. Inendocytosis,thematerialtobeinternalizedissurroundedbyanareaofplasmamembrane,whichthenbudsoffinsidethecelltoformavesiclecontainingtheingestedmaterial. Theterm"endocytosis"includeboththeingestionoflargeparticles(suchasbacteria)andtheuptakeoffluidsormacromoleculesinsmallvesicles. Theformeroftheseactivitiesisknownasphagocytosis(celleating)andthelatteraspinocytosis(celldrinking). 36 Dr/SherineFarouk.

[Audio] Types of Endocytosis: pinocytosis phagocytosis receptor mediated endocytosis 37 Dr/Sherine Farouk.

[Audio] Pinocytosis (cell drinking) Pinocytosis a biological process of taking in(engulfing) relatively small quantities of extracellular fluid . Occurs continuously and not molecule specific. For this reason it is called cell drinking It pinch off into vesicles, and fuse with lysosomes endocytic vesicle called a pinosome. 38 Dr/Sherine Farouk.

[Audio] Phagocytosis During the process of phagocytosis, the cell can be described as 'eating' invading pathogens as well as dead tissue and cell debris as part of the body's immune response to protect itself from illness. Studies have shown that most cells are in fact capable of carrying out phagocytosis. However, immune cells known as "professional phagocytes. The function of these cells is a vital part of the body's innate immune response and also plays a fundamental part in stimulating the adaptive immune response. The process of phagocytosis, therefore, is vital to the proper functioning of the immune system. 39 Dr/Sherine Farouk.

[Audio] Main steps of a macrophage ingesting a pathogen: a. Ingestion through phagocytosis, a phagosome is formed b. The fusion of lysosomes with the phagosome creates a phagolysosome; the pathogen is broken down by enzymes c. Waste material is expelled or assimilated. Dr/Sherine Farouk 40.

[Audio] Receptor-mediated Endocytosis Receptor-mediated endocytosis is a form of endocytosis in which receptor proteins on the cell surface are used to capture a specific target molecule. 41 Dr/Sherine Farouk.

[Audio] Receptor-mediated Endocytosis The most specific type of endocytosis Macromolecules binds to specific receptors on cell membrane This binding does not only signal invagination but also formation of protein coat called clathrin around the vesicle The vesicle is known as clathrin coated vesicle. The main purpose is to inject macromolecules that bind to the receptor Dr/Sherine Farouk 42.

[Audio] 43 Dr/Sherine Farouk. 43 Dr/Sherine Farouk.

[Audio] Cellular transport summary Transport Method Active/Passive Material Transported Diffusion Passive Small-molecular weight material Osmosis Passive Water Facilitated transport/diffusion Passive Sodium, potassium, calcium, glucose Primary active transport Active Sodium, potassium, calcium Secondary active transport Active Amino acids, lactose Phagocytosis Active Large macromolecules, whole cells, or cellular structures Pinocytosis and potocytosis Active Small molecules (liquids/water) Receptor-mediated endocytosis Active Large quantities of macromolecules 44 Dr/Sherine Farouk.