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Download Membrane Protein : Integral/Peripheral
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Membrane Protein : Integral/Peripheral • Integral Membrane Proteins (transmembrane) – Exposed to aqueous environment on both sides of the membrane – Used to transport molecules across membrane • Peripheral Membrane Proteins – Located on surface of a membrane – Eg. Cytoskeleton Passive Membrane Transport • No chemical energy required • Diffusion – Net movement of a substance from a region of high concentration to a region of low concentration until dynamic equilibrium between cells is met Simple Diffusion (Passive Transport) • Diffusion of small/non-polar molecules across plasma membrane without the help of an integral protein Facilitated Diffusion • Diffusion of large/polar molecules with the help of a transport protein (integral membrane protein) • Stops when equilibrium is reached • Two types of Transport (Integral) Proteins – Channel proteins – Carrier proteins • Channel Proteins Facilitated Diffusion – Form hydrophilic pathways in the membrane – Water and certain ions can pass – Voltage-gated channels • Open or closed by changes in voltage across the membrane or by binding molecules • Eg. Muscle contractions • Carrier Proteins Facilitated Diffusion – Form pathways through the membrane – Bind to a specific solute (glucose, amino acid) – Carrier protein changes shape allowing solute to move from one side of the membrane to the other Simple vs Facilitated • Simple Diffusion – Rate of diffusion increases as difference in concentration gradient increases • Facilitated Diffusion – Maximum rate is reached but limited by number of transport protein in membrane Osmosis • Passive diffusion of water across a membrane via aquaporins • Water always diffuses from an area of low solute concentration (high water concentration) to an area of greater solute concentration (low water concentration) • Three Types of Solutions – Hypotonic – Hypertonic – Isotonic Hypertonic Solutions • Solution that has a greater concentration of solute (dissolved substance) than what is being compared • Dehydration occurs because body fluids contain too much solute (salt) • Lead to liver/kidney failure • Hypertonic IV fluids are used to restore electrolyte balance Hypotonic Solutions • Solution that has a lesser concentration of solute (dissolved substance) than what is being compared • Hypotonic IV’s are used to treat true dehydration (water loss) • Water will move into our cells Isotonic Solutions • Solution that has an equal concentration of solute (dissolved substance) than what is being compared • Isotonic IV’s are used to increase fluid in blood • Maintain homeostasis (equilibrium) Exocytosis • Vesicles are used to transport • ATP is required • Transport of soluble proteins, membrane proteins and lipids • Degranulation – Cells release antimocrobial cytotoxic molecules – Immune response – Histamine (allergic reaction) Endocytosis • Transport of molecules inside cell – Large polar molecules • Pinocytosis – ECF and molecules • Phagocytosis – Immune response – Macrophage • Receptor-mediated – Clathrin (protein) assists in ingestion of specific molecules inside cell