Post on 14-Dec-2015
Membranes
Cell membrane = Plasmalemma = Plasma membrane
Surrounds cells and most organelles
Forms a network of passages
Mitochondria, chloroplasts, and the nucleus all have a double membrane
Functions of plasmalemma
1. Keep cell contents together and separate from other cells
2. Controls movement of substances into and out of cells
3. Allow communication between cells
4. Attachment for intracellular cytoskeleton, cell walls and intercellular adhesions
Membranes are made of Phospholipids
Hydrophilic Polar head
Hydrophobic Non-polar tails
Hydrophobic tails
Hydrophilic heads
Watery cytosol
Water outside cell
Hydrophobic tails
Watery Cytoplasm
Fluid mosaic theory
• Phospholipids are not bound to each other
• Like oil on water
• Water inside and outside the cell
http://www.youtube.com/watch?v=ULR79TiUj80&feature=related
(fluid mosaic model, 1.5 min)
Permeability
Membranes are selectively permeable
Allow some molecules through but not all
Permeability of membrane
Some membranes impermeable (eg surfaces designed to retain water such as skin, scales, exoskeletons)
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Key wordsPhospholipidsBilayerFatty tailsPhosphate headImpermeablePermeableLarge moleculesIonsFluid Mosaic
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(VERY) Quick quiz1. ____ are the main component of membranes 2. They consist of hydrophobic ____3. And a hydrophilic ____4. They also have integral and peripheral ____
Answers
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(VERY) Quick quiz1. Phospholipids are the main component of
membranes
2. They consist of hydrophobic tails3. And a hydrophilic head4. They also have integral and peripheral proteins
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Exercise
Workbook pp50-52, qq18-20 and 22-23Booklet p3
READING• Pathfinder p48 (or p42) Enzymes & reaction
rate• Excellence in Biology pp114-6
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Videos
http://www.youtube.com/watch?v=E90D4BmaVJM&feature=related
(10 min, includes biotechnology)http://www.teachersdomain.org/asset/tdc02_int_membraneweb/
(interactive - membrane)
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Glycoproteins & glycolipids for cell recognitionhttp://www.5min.com/Video/Proteins-as-the-Mosaic-of-the-Cell-Membrane-150624158 Back to
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Peripheral proteins
Partially embedded intrinsic – inside cell extrinsic – outside cell
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OIL AND WATER
I told you this would be important!
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Trans-membrane (integral) proteins
• involved in facilitated and active transport
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