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Cell Membranes & Walls Types of Cells Prokaryotes • Archaebacteria • Eubacteria * Eukaryotes • Plants * • Animals * • Fungi • Protists Why do cells have a membranes/walls? Functions of Cell Membrane 4 • Separates & protects cell from its surrounding environment • Protein molecules inside the cell membrane act as channels & pumps that move different molecules into & out of the cell. • Receptor proteins in cell membrane allow cells to detect external signaling molecules such as hormones Evolution of Cell Membrane 4 Current Theory: 1st prokaryotic cell membrane was a single layer of lipids Phospholipid • Hydrophilic Head (Polar) : Polar Group + Phosphate + Glyerol • Hydrophobic Tail (Non Polar) : 2 Fatty Acid Chains To Try... 1. Use a disposable pipet to place a drop of water on the 2 different kinds of spoons 2. Sketch & Describe what you see Phospholipid Bilayer When phospholipids are placed in water they usually form a sphere. To Try... 1. Fill a petri dish halfway with water 2. Use a disposable pipet to drop oil onto the water 3. Sketch and describe your observations Modern Bacteria Cell Membrane Phospoholipid Bilayer Cell Membrane Proteins Protein functions: • Transport nutrients, waste, gases, etc. • Chemical Receptors for the cell Cell Membrane Characteristics • Semi-permeable: the membrane allows the movement of some, but not all particles Cell Membrane Characteristics Fluid Mosaic Model: it is a lot of small components that together make the cell membrane http://home.earthlink.net/~shalpine/anim/Life/memb.htm Bacteria Cells 7 Gram Positive & Gram Negative Cell Wall & Membrane Bacteria Cells Gram Positive: Phospholipid Bilayer + Thick Cell Wall (Peptidoglycan) Gram Negative: Phospholipid Bilayer + Thin Cell Wall + Phospholipid Bilayer Gram-positive Cell Wall 8&9 • Cell Wall: made of peptidoglycan (murein) = polymer of sugars & amino acids • Cell Membrane: Phospholipid Bilayer is made of phoshates and lipid molecules Gram-Negative Cell Wall What is different? Gram Staining Protocol: 1) Apply a primary stain (crystal violet or methylene blue) to bacteria 2) Add Mordant (Gram's iodine) & let stand for 10-60 seconds, then pour off excess 3) Rapid decolorization w/ alcohol or acetone, rinse after 5 seconds (TIME CRUCIAL) 4) Counterstain w/ safranin or basic fuchsin for 40- 60 seconds, wash excess Gram Staining Gram Staining Gram Positive: Purple Gram Negative: Pink Endosymbiotic Theory 5 Organelles orginated as seperate prokaryotic organisms which were taken inside the cell as endosymbionts • Mitochondria developed from proteobacteria • Chloroplasts evolved from cyanobacteria Endosymbiotic Theory 6 Eukaryotic Cell Membrane 1 Eukaryotic Cell Membrane 2 What is similar between this cell membrane and the bacterial cell membrane? Plant Cell Wall 10 Cell Wall • thick & rigid • prevents enlargement of the plant cell • helps the plant absorb, transport, & secrete substances Cell Membrane Plant Cell Wall Pectin: Hemicellulose: Cellulose Microfibril: Sources 1. http://www.elsomresearch.com/images/nanosomin/membrane.gif 2. http://home.earthlink.net/~dayvdanls/membrane1.GIF 3. http://www.williamsclass.com/SeventhScienceWork/ImagesCells/CellMembrane.jpg 4. http://en.wikipedia.org/wiki/Cell_(biology) 5. http://en.wikipedia.org/wiki/Endosymbiotic_theory 6. https://eapbiofield.wikispaces.com/file/view/endosymbiosis.jpg 7. http://www.cehs.siu.edu/fix/medmicro/pix/walls.gif 8. http://www.palaeos.com/Kingdoms/Prokaryotes/Images/GramPosCellEnvelope.gif 9. http://www.mansfield.ohio-state.edu/~sabedon/007gpce.gif 10. http://www.mansfield.ohio-state.edu/~sabedon/007gpce.gif Cell Membranes are like Bubbles... Challenge: 1. Get a paper clip through the bubble without popping the bubble 2. Get a pencil through the bubble without getting it wet Soap Membrane How does the soap membrane compare to the cell membrane? Soap in Action Captures the lipid