Download - Chapter 4 notes new
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Chapter 4 Notes
Cells and Their Environment
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Molecules need to move across membranes in cells…
Image modiified from: http://www.accessexcellence.org/AB/GG/importProt.html
INfoodcarbohydratessugars, proteinsamino acidslipidssalts, O2, H2O
OUTwasteammoniasaltsCO2
H2O products
How does that happen?
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I. Passive Transport
• Passive Transport-the movement of substances across the cell membrane without the use of energy by the cell.
• There are many types of passive transport:
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A. Diffusion
• Diffusion- is the movement of a substance from an area of high concentration to an area of low concentration.
• Diffusion will eventually cause substances to be balanced (equilibrium) on both sides of the cell membrane.– Ex: ink or food coloring moving through water.
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Diffusion-high to low concentration.
Animatioin from: http://www.biologycorner.com/resources/diffusion-animated.gif
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B. Osmosis
• Osmosis- is the diffusion of water molecules across a selectively permeable membrane. (Egg Experiment)
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• 1. Hypotonic-solute outside cell less than inside; water moves into cell; cell swells
• 2. Hypertonic-solute outside cell greater than inside; water moves out of cell; cell shrinks
• 3. Isotonic-solute outside cell equals inside; no net movement of water.
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HYPOTONIC ISOTONIC HYPERTONIC
solute outside ‹ inside
Net movement of water into cell
Animal cells: swell & burst = CYTOLYSISPlant cells increase TURGOR PRESSURE
solute outside = inside
Net movement of water in and out of cell is equal
No change in size
solute outside > inside
Net movement of water out of cell
Animal cells: shrink = CRENATIONPlant cells: can’t shrink due to cell wallCell membrane pulls away from cell wall= PLASMOLYSIS
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C.Facilitated Diffusion• Facilitated Diffusion-when a membrane
protein helps to transport a substance across a cell membrane.
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1. Ion Channels-proteins that have a pore through which ions such as sodium, calcium, potassium can cross the cell membrane.
Types of Facilitated Diffusion
Animation from: http://www2.uic.edu/~myilma1/ionchannel.gif
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Types of FacilitatedDiffusion
2. Carrier protein-proteins that bind to specific substances, carry it across the cell
membrane, and release it.Animation from: http://bio.winona.edu/berg/ANIMTNS/facdifan.gif
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II. Active Transport
• Active Transport-the movement of a substance into an area of higher concentration by using energy from the cell in the form of ATP.
• There are many types of active transport:
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1. Sodium-Potassium pump• sodium ions are pumped out of the cell.• Potassium ions are pumped into the cell.
http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/eustruct/images/sppump.gif
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http://www.accs.net/users/kriel/chapter%20nine/
Animation from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/cell-movement.html
• 2. Endocytosis-substances that are too large to move into the cell membrane are moved by a vesicle that forms around it.
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• 3. Exocytosis-substances that are too large to move out of the cell membrane are released by a vesicle that forms around it.
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• 4. Membrane Receptor Proteins-proteins that help cell communicate with each other.
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rectpr.htm