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Transcript of 1 Cell Transport copyright cmassengale. Check Your Understanding At the end of today’s lesson, you...
1
Cell TransportCell Transport
copyright cmassengale
Check Your Understanding
At the end of today’s lesson, you should be able to
answer the following questions:
• What are the parts of the cell membrane and what do they do?
• What is the “Fluid Mosaic Model?”• Describe the processes of diffusion, osmosis,
facilitated diffusion, and active transport.
Cell Membrane
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Regulates passage of materials into and out of the cell
Parts of the membrane:
A) lipid bilayer (2 layers)B) proteinsC) cholesterolD) carbohydrate chains
Lipid Bilayer• Made of 2 sheets of
phospholipids, a type of lipid with a head and 2 tails
• Hydrophilic (water loving) head
• Hydrophobic (water fearing) tail
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Why do the phospholipids arrange themselves in a bilayer?
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• Membrane Proteins: Act as channels for large particles to enter and leave the cell
• Fluid-Mosaic Model: describes the flexibility of the lipid bilayer with a mosaic of proteins and other molecules
6..\..\..\Downloaded Videos\Fluid mosiac model.avi
Carbohydrate Chains
• Recognize parts of molecules to determine what molecules can be brought into the cell
• Can be attached to proteins or phospholipids
• Lock and Key Fit!
Label the Parts of the Membrane!• Outside cell• Inside cell• Phospholipid • Protein• Carbohydrate Chain
Function of the Cell Membrane
• Regulates what enters and leaves the cell
• Provides protection and support
Random Transition…AHHHH!
• This may seem completely rando…but I promise the dots will connect later!
Concentration
• In a solution, the concentration is the mass of solute in a given volume of solution
• A difference in concentration over a distance is called a concentration gradient
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Simple DiffusionSimple Diffusion
• Description: Molecules move from area of HIGH to LOWHIGH to LOW concentration
• This means they are going DOWN the CONCENTRATION GRADIENT
• PASSIVE Process (no energy required)
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..\..\..\Downloaded Videos\Diffusion.avi
Simple Diffusion of a Solute Across a Membrane
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Can all solutes cross the membrane by simple
diffusion?• NO!
• The membrane is selectively permeable, this means only certain solutes (typically small ones) can pass across by simple diffusion
• The solution? – Channel Proteins!
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Facilitated Diffusion• Description: Diffusion of certain molecules
through a selectively permeable membrane, made possible by protein channels
• PASSIVE Process• DOWN gradient
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OsmosisOsmosis• Description: Diffusion of WATER across a selectively
permeable membrane
• PASSIVE process
• DOWN GRADIENT (that is, WATER moves down its gradient)
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Cell in Isotonic SolutionCell in Isotonic Solution
CELLCELL
10% solute
90% water
10% solute90% water
What is the direction of water movement?
The cell is at EQUILIBRIUM.
ENVIRONMENTENVIRONMENT
Solution outside the cell has the SAME solute (and water) concentration as the cell itself
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Cell in Hypotonic SolutionCell in Hypotonic Solution
CELLCELL
10% solute
90% water
20% solute80%
water
What is the direction of water movement?
ENVIRONMENTENVIRONMENT Solution outside the cell has a LOWER solute (HIGHER water) concentration than the cell itself
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Cell in Hypertonic SolutionCell in Hypertonic Solution
CELLCELL
15% solute
85% water
5% solute95%
water
What is the direction of water movement?
ENVIRONMENTENVIRONMENT Solution outside the cell has a HIGHER solute (LOWER water) concentration than the cell itself
Isotonic Solution
NO NET MOVEMENT OF
H2O (equal amounts entering & leaving)
Hypotonic Solution
Cell Bursting
Hypertonic Solution
Cell Shrinking..\..\..\Downloaded Videos\Onion Cells Plasmolysis.avi
..\..\..\Downloaded Videos\Red Blood Cells in Hypotonic Solution.avi
..\..\..\Downloaded Videos\Red Blood Cells in a Hypertonic Solution.avi
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Osmosis in Red Blood CellsOsmosis in Red Blood Cells
IsotonicIsotonic Hypotonic Hypertoniccopyright cmassengale
Osmosis in Plant Cells
Active Transport
• Description: Movement of materials from LOW to HIGH concentration
• ACTIVE process (uses energy)
• UP Concentration Gradient
Active TransportMolecular Pumps
ATP
Molecular pumps are membrane proteins that use energy from ATP to move molecules across cell membranes. (Each pump moves one type of molecule)
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Endocytosis vs. Exocytosis
• Endocytosis: taking large amounts of material into the cell
• Exocytosis: sending large amounts of material out of the cell
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Endocytosis:Phagocytosis & Pinocytosis
Phagocytosis: The membrane folds to enclose solid particle (cell eating)
Pinocytosis: The membrane folds to enclose liquid with dissolved materials (cell drinking)
• In endocytosis, the membrane pinches in to form a vesicle
• The vesicle may later join with a lysosome so that particles can be “digested”
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Vesicles
Exocytosis1
Products of the ER are packaged in vesicles at the Golgi and released at the cell membrane.
..\..\..\Downloaded Videos\Endocytosis & Exocytosis.avi
Cell Membrane and Homeostasis
• Refresher from Characteristics of Life…what is homeostasis?
• How does the cell membrane help organisms to maintain homeostasis?