Lecture #3Date ______
description
Transcript of Lecture #3Date ______
Lecture #3 Date ______
Chapter 8~Membrane Structure & Function
Voyage through a cell
http://www.youtube.com/watch?v=GW0lqf4Fqpg
Golgi http://www.youtube.com/watch?v=K7yku3
sa4Y8
Choroplast and Mitochondrion
Cell Junctions
Contractile vacuole: http://www.youtube.com/watch?v=iG6Dd3
COug4&NR=1 Cilia and flagellates http://www.youtube.com/watch?v=E1L27s
UzwQ0
Membrane structure, I Selective permeability Amphipathic~
hydrophobic & hydrophilic regions
Singer-Nicolson: fluid mosaic model
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
Membrane structure, III Membrane protein
function: •transport•enzymatic activity•signal transduction•intercellular joining•cell-cell
recognition •ECM attachment
Marker proteins are also membrane proteins
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?
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
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
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?
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
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
Video of the cell working
http://www.youtube.com/watch?v=5ukPD4G5eSw&NR=1
Receptor mediated endocytosis using coated pits
Multiple receptors
Concentrates molecules for endocytosis