lecture #3date ______ chapter 8~ membrane structure & function
TRANSCRIPT
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Lecture #3 Date ______
Chapter 8~Membrane Structure & Function
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Voyage through a cell
http://www.youtube.com/watch?v=GW0lqf4Fqpg
Golgi http://www.youtube.com/watch?v=K7yku3
sa4Y8
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Choroplast and Mitochondrion
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Cell Junctions
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Contractile vacuole: http://www.youtube.com/watch?v=iG6Dd3
COug4&NR=1 Cilia and flagellates http://www.youtube.com/watch?v=E1L27s
UzwQ0
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Membrane structure, I
Selective permeability Amphipathic~
hydrophobic & hydrophilic regions
Singer-Nicolson: fluid mosaic model
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Membrane structure, II
Phospholipids~ membrane fluidity Cholesterol~ membrane stabilization “Mosaic” Structure~ Integral proteins~ transmembrane
proteins Peripheral proteins~ surface of
membrane Membrane carbohydrates ~ cell to
cell recognition; oligosaccharides (cell markers); glycolipids; glycoproteins
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Membrane structure, III
Membrane protein function:
•transport•enzymatic activity•signal transduction•intercellular
joining •cell-cell recognition •ECM attachment
Marker proteins are also membrane proteins
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Questions
Describe the polarity of an integral protein.Why does a protein for cell recognition never
flip sides by going “inside-out”?Why can phopholipids switch places with
their neighbor to the left and right, but not across from each other?
Why is cholesterol located where it is in the plasma membrane?
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Membrane traffic Diffusion~ tendency of any
molecule to spread out into available space
Concentration gradient: High to low
Passive transport~ diffusion of a substance across a biological membrane
Osmosis~ the diffusion of water across a selectively permeable membrane
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Water balance Osmoregulation~ control
of water balance
Hypertonic~ higher concentration of solutes
Hypotonic~ lower concentration of solutes
Isotonic~ equal concentrations of solutes
Cells with Walls: Turgid (very firm)
Flaccid (limp)
Plasmolysis~ plasma membrane pulls away from cell wall
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Questions
Why do grocery stores spray their vegetables with water?
Why does your skin “prune” when you swim all day at the pool?
Why does your skin crack when you spend all day at the ocean?
Why do trees in the tropics have big leaves compared to dessert trees?
When a plant “wilts”, are its cells turgid or flaccid?
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Specialized Transport
Transport proteins Facilitated diffusion~
passage of molecules and ions with transport proteins across a membrane down the concentration gradient
Active transport~ movement of a substance against its concentration gradient with the help of cellular energy
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Types of Active Transport
Sodium-potassium pump Exocytosis~ secretion of
macromolecules by the fusion of vesicles with the plasma membrane
Endocytosis~ import of macromolecules by forming new
vesicles with the plasma membrane
•phagocytosis (eating)•pinocytosis (drinking)•receptor-mediated
endocytosis
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Video of the cell working
http://www.youtube.com/watch?v=5ukPD4G5eSw&NR=1
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Receptor mediated endocytosis using coated pits
Multiple receptors
Concentrates molecules for endocytosis