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Obtaining Ions, Nutrients and Water
Cellular Transport Obtaining Ions, Nutrients and Water
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Plasma (Cell) Membrane
semipermeable membranes regulate cell interaction with surroundings
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small openings (pores) allow certain molecules to penetrate cell but denies others making it semi
Small black molecules allowed through Large red molecules NOT allowed through WHY?
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2 layers = 1 plasma membrane
Plasma membrane is composed of a phospholipid bilayer (two layers of phospholipids or lipids with phosphates) 2 layers = 1 plasma membrane
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Phospholipids composed of:
lipids (fats): glycerol group and two fatty acid straight tails Nonpolar / hydrophobic (water-fearing), can’t dissolve in water, found in interior of plasma membrane Phosphate head Lipid tails
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phosphate group: phosphate (PO4)
Polar / hydrophilic (water-loving) globular heads, form outside of membrane (can be exterior or interior side of cell) Can dissolve in water, allows plasma membrane of cell to interact with watery environment of cell. Phosphate head Lipid tail
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properties of phospholipids do NOT allow water-soluble molecules to move through membrane easily.
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H2O soluble H2O soluble
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Proteins embedded within membrane move about in a fluid fashion
Fluid mosaic model explains how structural properties of plasma membrane allow lipids & proteins to move freely in membrane Mosaic: something consisting of variety of components
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Plasma membrane also contains:
Transport proteins: allow substances or waste materials to move through plasma membrane Proteins & carbohydrates: stick out from cell and help cells identify each other Proteins: give cell flexibility Carbohydrates: act as identifier of cell type
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Homeostasis Cell constantly interacts with environment & has to respond to external conditions to maintain homeostasis Increase in heat makes temperature rise 99.0ºF 98.8ºF 98.6ºF Cell will seek to cool itself down Homeostasis at work!
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Eating a bag of chips will cause cell to respond to new salty condition
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Cell membranes maintain homeostasis by regulating passage of materials into and out of the cell:
Passive Transport – no energy required to move solute or solvent from high to low concentration (down concentration gradient) Active Transport – energy required to move solute from low to high concentration (against concentration gradient) Outside Cell (16) Inside Cell (4)
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concentration gradient = difference in amount of substance present inside the cell versus outside the cell outside inside
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Molecules will freely flow from high concentration to low concentration
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Concentration Gradient
Pathway from high to low concentration is concentration gradient Eventual point where concentration is equal = equilibrium (particles still randomly move but equal in/out) Concentration Gradient High Concentration Low Concentration
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Passive Transport Three methods:
Simple diffusion – particles (solutes) Osmosis – diffusion of water (solvent) Carrier-facilitated diffusion – particles (solutes) with protein assistance
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Simple Diffusion Simple diffusion – free movement of ions & molecules through protein channels in membrane Outside cell Inside cell
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Simple Diffusion – the homemade animation
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Osmosis Osmosis – free movement or diffusion of solvent (water) ONLY
Note how the red sugar particles stay put. Only the blue water molecules move.
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Osmosis– the homemade animation
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three types of solutions that determine direction of water :
isotonic solution hypotonic solution hypertonic solution
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Isotonic Solution concentration of water on outside of cell is same as on inside of cell Cells do not experience overall osmosis (or diffusion) retain their normal shape, Still random movement for an overall net gain of 0
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ISOTONIC SOLUTION 90% H2O 10% particles (inside cell) 90% H2O
(outside cell) ISOTONIC SOLUTION
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Hypotonic Solution concentration of water is higher outside cell than concentration of water inside cell. Cells experience osmosis (and diffusion) water moves into cell cell swells and will burst if animal cell but will not burst if plant cell due to cell wall
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Diffusion of particles
30% H2O 70% particles (inside cell) Osmosis of water Diffusion of particles 70% H2O 30% particles (outside cell) HYPOTONIC SOLUTION
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Hypertonic Solution concentration of water is higher inside cell than concentration outside cell. Cells experience osmosis (and diffusion) water moves out of cell Cells shrink Plant wilts because of a decrease in pressure on cell wall
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Diffusion of particles
55% H2O 45% particles (inside cell) Osmosis of water Diffusion of particles 45% H2O 55% particles (outside cell) HYPERTONIC SOLUTION
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Hypertonic vs. Isotonic vs. Hypotonic Solutions
Higher solute OUTSIDE Equal solute Higher solute INSIDE Higher water INSIDE Equal water Higher water OUTSIDE Water moves OUT No net movement Water moves IN Cell SHRINKS Normal Cell SWELLS
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Hypertonic vs. Isotonic vs. Hypotonic Solutions
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Hypertonic vs. Isotonic vs. Hypotonic Solutions
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Hypertonic vs. Isotonic vs. Hypotonic Solutions
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Diffusion and Osmosis are Simultaneous!
Often times, diffusion of large particles can’t happen or happen fast enough Water will diffuse via osmosis to regulate concentration (PERCENTAGES) Outside cell is 50% solute, 50% water Inside cell is 10% solute, 90% water Solute is too big to move. Will we die? No. Water will move to get concentration equal
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Particles Can’t Move What will Happen?
90% H2O 10% particles (inside cell) 50% H2O 50% particles (outside cell) Hint: look at water % only. Where will the water go?
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Diffusion of particles
Question1: Which way will the particles move? outside Question 2: Which way will the water move? 20% H2O 80% particles (inside cell) inside Osmosis of water Diffusion of particles 80% H2O 20% particles (outside cell)
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Analyze the following picture. What will happen?
DIFFUSION OSMOSIS
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Analyze the following picture. What will happen?
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Carrier-Facilitated Diffusion
free movement of larger molecules with aid (help) of a transport/carrier protein Large solutes (sugars, amino acids) are too big to go through plasma membrane unaided
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Facilitated Diffusion – the homemade animation
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ACTIVE TRANSPORT Needs energy (ATP) to move particles across plasma membrane Three types: Active transport – small molecules AGAINST concentration gradient (from low to high) Endocytosis – large molecules being engulfed by plasma membrane into vesicles Exocytosis – large molecules being expelled out by vesicles out of plasma membrane
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Active Transport Requires energy (ATP) to move materials against gradient (low to high concentration) carrier protein allows specific molecule or ion to bind Example: sodium/potassium (Na/K) pump ATP changes shape of protein to move molecule or ion across plasma membrane ATP
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Endocytosis cell surrounds material with a portion of its plasma membrane and forms a vesicle Vesicle moves particle inside cell for digestion Bacteria, food Phagocytosis – large, solid particles Pinocytosis – small, liquid particles
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Active Transport of People
STARRING train as the CELL platform as the EXTRACELLULAR SPACE people as the PARTICLES conductors as the ATP
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Exocytosis Vesicle brings material to cell membrane & expels (secretes) it Wastes, hormones
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Passive vs. Active Overview
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The End
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