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Transcript
Movement Through the Membrane •The Cell boarder is very important •It regulates what enters and leaves the cell. •It provides protection and support. Functions of the cell membrane. •1. Provides boundary for cell •2. Selectively permeable- only allows certain things to pass through- “Picky” Ex. Window screen •3. Maintains homeostasis: balance within the cells The Cell Membrane • • • Membrane is a lipid bilayer Phospholipids: fatty areas that attract (hydrophilic) and repel (hydrophobic) water Embedded proteins: “club bouncers” – Decides what goes in & out – Markers for recognition The lipid bilayer has proteins embedded in it. Cell Membrane Proteins Protein channel Carbohydrate chains Lipid bilayer • Passive transport: Diffusion - the movement of a substance from an area of high concentration to an area of lower concentration (a concentration gradient). PASSIVE TRANSPORT = NO energy 1. Diffusion: movement of particles from high to low concentration Water Molecule Sugar Molecule High concentration Ex. Perfume & Body odor 2. Osmosis: movement of water from high to low concentration. •-Turgor Pressure- cell explode Low concentration Both occur through bilayer and Do NOT require cell energy. Movement occurs until equilibrium is reached. • Osmotic pressure always moves water toward the hypertonic side (the side containing the least amount of water) of a membrane. Three Strengths of Solutions. • Isotonic • Hypotonic • Hypertonic • ISOTONIC: • particles outside = particles inside • ISO- means “equal to” • Movement into cell= movement out of cell •HYPOTONIC: concentration of dissolved substances is lower outside cell than inside cell •HYPO = “below strength” •Water will move INTO cell causing it to swell - water always moves to areas of greater concentration (more “stuff”) •Cells could rupture if the cell takes in too much water •This increases pressure inside of cell = TURGOR PRESSURE Hypo –Hippo •HYPERTONIC: concentration of dissolved substances is higher outside the cell •HYPER = “above strength” •Water rushes OUT of cell causing it to shrivel (water rushes to where there is more substances) •Can result in PLASMOLYSIS in plants which causes wilting Red Blood Cells Remember! • Osmosis & Diffusion are passive transport!! Meaning the cell does not have to use any energy to perform these! Active Transport. • transport against concentration gradient; goes from low to high concentration • Go through protein channel • This requires energy to move them into cell; ex: Na-K pump Molecule to be carried Low Concentration High Concentration Molecule being carried Energy •Types of active transport: http://www.linkpublishing.com/videotransport.htm#LINKS_ •ENDOCYTOSIS: cells take in large clumps of substances •Phagocytosis: “cell eating” take in food •Pinocytosis: “cell drinking” take in water •EXOCYTOSIS: cells move substances out (exit) ex: wastes Cell Eating Cell Drinking High Concentration Glucose molecules •FACILITATED TRANSPORT: •type of diffusion as movement is from high to low concentration •this type goes through a protein channel rather than bilayer. Low Concentration Protein channel •Proteins –picky “bouncers” Summary • Diffusion & Osmosis – high to low concentration – goes in between phospholipid spaces – no energy= Passive transport • Active transport– low to high concentration – requires energy – goes through protein • Facilitated Transport– high to low concentration – no energy – goes through protein ` Summary • Ex. Party 1. Air coming into a window screen 2. Someone opens the door & you walk through (door represents protein) 3. someone goes through the back door that is already open coming in=Endocytosis going out= Exocytosis • Summary