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The Plasma Membrane - Gateway to the Cell Photograph of a Cell Membrane Types of Transport Across Cell Membranes Simple Diffusion • Requires NO energy • Molecules move from area of HIGH to LOW concentration DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY Diffusion of Liquids Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) Osmosis • Diffusion of water across a membrane • Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O NO NET MOVEMENT What is the direction of water movement? equilibrium The cell is at _______________. Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? Cells in Solutions Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS Hypertonic Solution PLASMOLYSIS Cytolysis & Plasmolysis Cytolysis Plasmolysis Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic hypotonic hypertonic isotonic hypertonic isotonic hypotonic Three Forms of Transport Across the Membrane Passive Transport Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. Proteins Are Critical to Membrane Function Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential Moving the “Big Stuff” Exocytosis - moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve cells communicate with one another. Exocytosis Exocytic vesicle immediately after fusion with plasma membrane. Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis. Pinocytosis Most common form of endocytosis. Takes in dissolved molecules as a vesicle. Pinocytosis • Cell forms an invagination • Materials dissolve in water to be brought into cell • Called “Cell Drinking” Example of Pinocytosis pinocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue). Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. Receptor-Mediated Endocytosis Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” Phagocytosis About to Occur Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment OSMOSIS http://www.biology4kids.com/files/cell_main.html Diffusion http://lhs.lps.org/staff/sputnam/Biology/U3Cell/diffusion_1.png See a video clip about DIFFUSION-7A Animatioin from: http://www.biologycorner.com/resources/diffusion-animated.gif Molecules move FROM A LOT _______“where there’s _______” to NOT ____“where there’s _______” DIFFUSION across a space Happens anytime there is a __________ DIFFERENCE in concentration in one place compared to another Concentration gradient = ________________________ DIFFUSION across a SPACE • Molecules move automatically _______ DOWN the concentration gradient _______ an from area of _______ Higher concentration ____ to an area of ________ concentration Lower • EXAMPLES Blue dye in beaker demo, Someone making popcorn/grilling out Strong perfume, Bad smell in room http://leighhouse.typepad.com/blog/images/kool_aid.jpg http://www.swapmeetdave.com/Humor/Farts.htm DIFFUSION across a space Diffusion continues until the concentration equal everywhere is ________________ in space Equilibrium = ________________________ http://lhs.lps.org/staff/sputnam/Biology/U3Cell/diffusion_1.png Molecules need to move across membranes in cells Image modiified from: http://www.accessexcellence.org/AB/GG/importProt.html across Diffusion can happen ________ a membrane _____________ in a cell, too …as long as membrane will let the molecule pass through _________________ Video from: http://www.southtexascollege.edu/tdehne/BC_ShockwaveAnimations/08SWF-MembraneStructureAndFunct/08-02-MembraneStructure.swf SELECTIVELY PERMEABLE (Semi-permeable) See a movie http://life.nthu.edu.tw/~d857401/advance.html CELL EXAMPLE: DIFFUSION automatically moves oxygen from HIGHER concentration (in lungs) to a LOWER concentration (in blood) CO2 automatically moves from where there is a HIGHER concentration (in blood) to where there is a lower concentration (in lungs) http://www.le.ac.uk/pa/teach/va/anatomy/case2/2_2.html BUT…. What if a cell needs to LARGE or ______ POLAR move _____ molecules? http://www.d.umn.edu/~sdowning/Membranes/membraneImages/jpegimages/diffusionmedium.jpg What if cell needs to move a AGAINST the molecule _________ CONCENTRATION GRADIENT? _______________ (LOWER HIGHER) Cell example: Want to put MORE glucose into mitochondria when there is already glucose in there Image from: http://www.biologyclass.net/mitochondria.jpg What if cell needs to move FAST molecules really _______? (can’t wait for it to diffuse) Cell example: Movement of Na + & K+ ions required to send nerve signals http://www.steve.gb.com/images/science/neuron.png WAY to ____ HELP We need a ____ molecules across cell can’t go membranes that _______ themselves across by ___________ Kidspiration by: Riedell PASSIVE Transport Kinds of ________ •__________________________________ Diffusion •Osmosis ___________________________________ •Facilitated Diffusion ___________________________________ DIFFUSION across a membrane DIFFERENCE Happens anytime there is a __________ in _____________ concentration on one side of the membrane compared to the other Molecules that move by diffusion across membranes in cells: ______________ OXYGEN ______________ CARBON DIOXIDE http://www.lionden.com/cell_animations.htm See diffusion animation OSMOSIS = SPECIAL KIND OF DIFFUSION IMAGE by RIEDELL OSMOSIS ____________ See osmosis animation DIFFUSION __________ Movement of molecules across a Semi-permeable membrane _________________ lower from ______ Higher concentration to _____ See a video about Passive transport 7-C Facilitated Diffusion Carrier proteins help diffusion go faster _______ FACILITATED DIFFUSION • No energy required = __________________ PASSIVE DOWN concentration gradient • Moves _________ from ________________________ HIGHER to LOWER Membrane proteins • _____________________ grab molecule, change shape, and flip to other side (Like a revolving door) • Molecules that move this way in cells: GLUCOSE _______________________ Facilitated Diffusion Animation from: http://bio.winona.edu/berg/ANIMTNS/facdifan.gif Kidspiration by: Riedell ACTIVE Kinds of ________Transport •________________________________________ Sodium-Potassium Pump •Endocytosis ___________________________________ ____________________________________ •Exocytosis See a video clip about Na+-K+ pump -7D Sodium (Na+)- Potassium (K+) Pump Animation from: http://www.lionden.com/cell_animations.htm See a movie about Na+ - K+ pump Sodium-Potassium pump • ___________ transport ACTIVE (requires energy from ______) ATP • Special just for Na+ and K + ions Carrier Proteins • Uses integral ___________________ to move molecules • Examples in nerve cells: Na+ is pumped out of cells at same time K + is taken into cells See a video clip about Endo/exocytosis -7E ENDOCYTOSIS Takes substances into cell ACTIVE • _____________transport energy from ______) ATP (requires __________ • Uses small membrane sacs called ______________ to carry substances VESICLES http://www.sirinet.net/~jgjohnso/cell.html 2 KINDS of ENDOCYTOSIS Takes substances into cell If taking in: PINOCYTOSIS fluid or small molecules =_________________ PHAGOCYTOSIS large particles or whole cells =______________ • Examples in cells: – one celled organisms eat this way – white blood cells get rid of bacteria this way Pinocytosis • Called “Cell Drinking” ENDOCYTOSIS Animation from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/cell-movement.html http://www.accs.net/users/kriel/chapter%20nine/ PHAGOCYTOSIS Called “Cell Eating” White blood cell ___________ germs destroying _______ EXOCYTOSIS Substances released outside of cell ACTIVE transport • __________ energy (requires __________) VESICLES • Substances move in____________ • Examples in cells: – _________ release packaged proteins GOLGI this way Exocytosis http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBooktransp.html Video: http://www.southtexascollege.edu/tdehne/BC_ShockwaveAnimations/07SWF-TourOfTheCell/07-16-EndomembraneSystem.swf GOLGI BODIES USE EXOCYTOSIS Animation from: http://www.franklincollege.edu/bioweb/A&Pfiles/week04.html See a Golgi movie Videos from: http://www.pleasanton.k12.ca.us/avhsweb/thiel/apbio/notes/chp8/exocytosis_endocytosis.mov http://trc.ucdavis.edu/biosci10v/bis10v/week2/endocytosis.mov Endocytosis & Exocytosis Watch a video clip about endo/exocytosis Watch a video clip about endo/exocytosis Choose Screen/Switch programs to view INSULIN being released by pancreas cells using exocytosis http://fig.cox.miami.edu/~cmallery/255/255ion/fig14x26.jpg What if there is a difference in concentration but solute molecules can’t move across a membrane? WATER will move until concentration reaches equilibrium VOCAB _____________ SOLUTE = substance that is dissolved in a solvent to make a solution SOLVENT = substance in which a _____________ solute is dissolved EX: Koolaid powder = solute Water = solvent Koolaid drink = solution http://www.makash.ac.il/h_school/hst/hstsb/chem/luach/dissolve.jpg Images by Riedell __________________ CONCENTRATION = mass of a solute in a given volume of solution MORE molecules there are in a given The _______ volume the ____________the concentration GREATER See a video clip about OSMOSIS -7B Animation: http://www.ouhscphysio.org/humanphys/animations/osmosis1.swf See an animation Osmosis1 http://faculty.etsu.edu/currie/images/osmosis1.jpg Animation from: http://www.ouhscphysio.org/humanphys/animations/osmosis4.swf OSMOSIS See an animation OSMOSIS 4 HYPERTONIC: Concentration outside cell is ____________________ inside cell GREATER THAN More water leaves cell than enters so cell ____________ shrinks Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? Animation from: http://www.ouhscphysio.org/humanphys/animations/osmosis3.swf OSMOSIS See an animation Osmosis3 HYPOTONIC: Concentration outside cell is ________________ LESS THAN inside the cell More water enters than leaves cell so cell will ___________________ Swell and possibly burst Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? OSMOSIS ISOTONIC: EQUALS Concentration outside cell __________ concentration inside cell Water entering = water leaving STAYS THE SAME SIZE so cell _____________________ Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O NO NET MOVEMENT What is the direction of water movement? equilibrium The cell is at _______________. Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution Cell Swells & may burst Hypertonic Solution Cell shrivels up Animal cells http://www.stchs.org/science/courses/sbioa/metenergy/bloodcells.gif Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic http://www.stchs.org/science/courses/sbioa/metenergy/aplantturgor.gif Plant cells CELL WALL _____ keeps Plant cells from bursting VACUOLES store WATER http://www.biology4kids.com/files/cell_vacuole.html OSMOTIC PRESSURE _____________________________ = Pressure exerted by water during osmosis SO WHAT? Bath water is ________________ hypotonic compared to you Sitting in the bathtub causes your fingers and toes to wrinkle up when water ________ enters your skin cells by osmosis Grocery stores spray water on their veggies to “plump them up” http://www.painetworks.com/photos/gt/gt0461.JPG SO WHAT?