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The Plasma Membrane - Gateway to the Cell
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Photograph of a Cell Membrane
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Types of Transport Across Cell Membranes
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Simple Diffusion Requires NO energy
Molecules move from area of HIGH to LOW concentration
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DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
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Diffusion of Liquids
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Diffusion through a Membrane
Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)
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Diffusion across a membrane Semipermeable membrane
Osmosis Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Semipermeable membrane
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Diffusion of H2O Across A Membrane
High H2O potential Low solute concentration Low H2O potential High solute concentration
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Cell in Isotonic Solution
10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________.
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Cell in Hypotonic Solution
10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement?
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Cell in Hypertonic Solution
15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement?
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Cells in Solutions
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NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS
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Cytolysis & Plasmolysis
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Osmosis in Red Blood Cells
Isotonic Hypertonic Hypotonic
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isotonic hypotonic hypertonic hypertonic isotonic hypotonic
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Three Forms of Transport Across the Membrane
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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.
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Facilitated diffusion
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.
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Proteins Are Critical to Membrane Function
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Active Transport Requires energy or ATP
Moves materials from LOW to HIGH concentration AGAINST concentration gradient
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Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump
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Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential
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Exocytosis- moving things out.
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.
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Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.
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Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis.
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Pinocytosis Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
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Pinocytosis Cell forms an invagination
Materials dissolve in water to be brought into cell Called “Cell Drinking”
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Example of Pinocytosis
mature transport vesicle pinocytic vesicles forming Transport across a capillary cell (blue).
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Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.
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Receptor-Mediated Endocytosis
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Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating”
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Phagocytosis About to Occur
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Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
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Exocytosis The opposite of endocytosis is exocytosis
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
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OSMOSIS
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Diffusion
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See a video clip about DIFFUSION-7A
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FROM A LOT to NOT Molecules move _______“where there’s _______”
Animatioin from: Molecules move _______“where there’s _______” ____“where there’s _______” FROM A LOT to NOT
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DIFFUSION across a space
Happens anytime there is a __________ in concentration in one place compared to another = ________________________ DIFFERENCE Concentration gradient
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DIFFUSION across a SPACE
Molecules move automatically _______ the concentration gradient _______ an area of _______ concentration ____ an area of ________ concentration EXAMPLES DOWN from Higher to Lower Blue dye in beaker demo, Someone making popcorn/grilling out Strong perfume, Bad smell in room
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DIFFUSION across a space
Diffusion continues until the concentration is ________________ in space = ________________________ equal everywhere Equilibrium
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Molecules need to move across membranes in cells
Image modiified from:
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Diffusion can happen ________ a _____________ in a cell, too
across membrane …as long as membrane will let the molecule _________________ pass through
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SELECTIVELY PERMEABLE (Semi-permeable)
Video from: SELECTIVELY PERMEABLE (Semi-permeable) See a movie
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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)
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BUT…. What if a cell needs to move _____ or ______ molecules?
LARGE POLAR
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What if cell needs to move a molecule _________ the CONCENTRATION GRADIENT? _______________
AGAINST (LOWER HIGHER) Cell example: Want to put MORE glucose into mitochondria when there is already glucose in there Image from:
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What if cell needs to move molecules really _______
What if cell needs to move molecules really _______? (can’t wait for it to diffuse) FAST Cell example: Movement of Na + & K+ ions required to send nerve signals
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We need a ____ to ____ molecules across cell membranes that _______ across by ___________
WAY HELP can’t go themselves
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Kidspiration by: Riedell
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Kinds of ________ Transport
PASSIVE __________________________________ ___________________________________ Diffusion Osmosis Facilitated Diffusion
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DIFFUSION across a membrane
DIFFERENCE Happens anytime there is a __________ in _____________ on one side of the membrane compared to the other concentration Molecules that move by diffusion across membranes in cells: ______________ OXYGEN CARBON DIOXIDE See diffusion animation
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OSMOSIS OSMOSIS DIFFUSION Semi-permeable lower
= SPECIAL KIND OF DIFFUSION IMAGE by RIEDELL OSMOSIS ____________ See osmosis animation DIFFUSION __________ Movement of molecules across a _________________ membrane from ______ concentration to _____ Semi-permeable lower Higher
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See a video about Passive transport 7-C
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Facilitated Diffusion _______ proteins help diffusion go faster
Carrier
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FACILITATED DIFFUSION
PASSIVE No energy required = __________________ Moves _________ concentration gradient from ________________________ _____________________ grab molecule, change shape, and flip to other side (Like a revolving door) Molecules that move this way in cells: _______________________ DOWN HIGHER to LOWER Membrane proteins GLUCOSE
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Facilitated Diffusion
Animation from:
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Kidspiration by: Riedell
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Kinds of ________Transport
ACTIVE ________________________________________ ___________________________________ ____________________________________ Sodium-Potassium Pump Endocytosis Exocytosis
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See a video clip about Na+-K+ pump -7D
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Sodium (Na+)- Potassium (K+) Pump
Animation from: See a movie about Na+ - K+ pump
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Sodium-Potassium pump
ACTIVE ___________ transport (requires energy from ______) Special just for Na+ and K + ions Uses integral ___________________ to move molecules Examples in nerve cells: Na+ is pumped out of cells at same time K + is taken into cells ATP Carrier Proteins
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See a video clip about Endo/exocytosis -7E
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ENDOCYTOSIS Takes substances into cell
ACTIVE _____________transport (requires __________ from ______) Uses small membrane sacs called ______________ to carry substances energy ATP VESICLES
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2 KINDS of ENDOCYTOSIS Takes substances into cell
If taking in: fluid or small molecules =_________________ large particles or whole cells =______________ Examples in cells: one celled organisms eat this way white blood cells get rid of bacteria this way PINOCYTOSIS PHAGOCYTOSIS
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Pinocytosis Called “Cell Drinking”
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ENDOCYTOSIS Animation from:
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PHAGOCYTOSIS Called “Cell Eating” ___________ destroying _______ germs
White blood cell germs ___________ destroying _______
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EXOCYTOSIS Substances released outside of cell
ACTIVE __________ transport (requires __________) Substances move in____________ Examples in cells: _________ release packaged proteins this way energy VESICLES GOLGI
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Exocytosis
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GOLGI BODIES USE EXOCYTOSIS
Video: GOLGI BODIES USE EXOCYTOSIS Animation from: See a Golgi movie
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Endocytosis & Exocytosis
Videos from: Endocytosis & Exocytosis Watch a video clip about endo/exocytosis Choose Screen/Switch programs to view
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INSULIN being released by pancreas cells using exocytosis
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What if there is a difference in concentration but solute molecules can’t move across a membrane?
WATER will move until concentration reaches equilibrium
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VOCAB _____________ = substance that is dissolved in a solvent to make a solution _____________ = substance in which a solute is dissolved SOLUTE SOLVENT EX: Koolaid powder = solute Water = solvent Koolaid drink = solution
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Images by Riedell __________________ = mass of a solute in a given volume of solution CONCENTRATION MORE The _______ molecules there are in a given volume the ____________the concentration GREATER
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See a video clip about OSMOSIS -7B
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See an animation Osmosis1
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OSMOSIS shrinks GREATER THAN
Animation from: OSMOSIS See an animation OSMOSIS 4 HYPERTONIC: Concentration outside cell is ____________________ inside cell More water leaves cell than enters so cell ____________ GREATER THAN shrinks
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Cell in Hypertonic Solution
15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement?
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OSMOSIS Swell and possibly burst LESS THAN
Animation from: OSMOSIS See an animation Osmosis3 HYPOTONIC: Concentration outside cell is ________________ inside the cell More water enters than leaves cell so cell will ___________________ LESS THAN Swell and possibly burst
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Cell in Hypotonic Solution
10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement?
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OSMOSIS ISOTONIC: Concentration outside cell __________ EQUALS
concentration inside cell Water entering = water leaving so cell _____________________ EQUALS STAYS THE SAME SIZE
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Cell in Isotonic Solution
10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________.
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NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Cell Swells & may burst Cell shrivels up
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Animal cells
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Osmosis in Red Blood Cells
Isotonic Hypertonic Hypotonic
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Plant cells _____ keeps CELL WALL Plant cells from bursting
Plant cells CELL WALL _____ keeps Plant cells from bursting
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VACUOLES store WATER OSMOTIC PRESSURE _____________________________ =
OSMOTIC PRESSURE _____________________________ = Pressure exerted by water during osmosis
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SO WHAT? hypotonic Bath water is ________________ compared to you
Sitting in the bathtub causes your fingers and toes to wrinkle up when water ________ your skin cells by osmosis enters
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Grocery stores spray water on their veggies to “plump them up”
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SO WHAT?
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