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Grade breakdowns—Period 5 A=4 B=5 C=13 F=3 (Mandatory tutoring) Build a cell membrane Aka lipid bilayer Aka plasma membrane LABEL 5 components Label outside and inside cell Pick up 2 different scripts from demo table (1 per 2 people) Practice with a partner What is the role of: -nucleus -RNA -ribosomes -rough ER -Golgi -transport vessicles Draw diagram Danish Review Make 4 higher level questions from 1) 2) 3) 4) Ecology Evolution Chemistry Cells how does ... compare/contrast with ...? what evidence can you list for ...? SYNTHESIS creating a unique, original product that may be in verbal form or may be a physical object combination of ideas to form a new whole what would you predict/infer from ...? what ideas can you add to ...? how would you create/design a new ...? what might happen if you combined ...? what solutions would you suggest for ...? EVALUATION making value decisions about issues resolving controversies or differences of opinion development of opinions, judgements or decisions do you agree that ...? what do you think about ...? what is the most important ...? place the following in order of priority ... how would you decide about ...? what criteria would you use to assess ...? Announcements Cells test moved to Thursday, Dec 1 Lab report due tomorrow Keep your Chapters 8 + 9 notes Answer a flashcard for 0.5 points Ch.7~MembraneStructure&Function Fluid mosaic model Exit Quiz: Membrane 1) Draw a membrane and label 5 components 2) Describe the role of 6 of the 6 membrane proteins Bonus: Explain the 4 levels of a protein Membrane structure, I Selective permeability Amphipathic~ hydrophobic & hydrophilic regions 1935 Davson Danielli sandwich model Singer-Nicolson: 1972 fluid mosaic model Cell membrane must be more than lipids… In 1972, S.J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer It’s like a fluid… It’s like a mosaic… It’s the Fluid Mosaic Model! Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Glycoprotein Extracellular fluid Glycolipid Phospholipids Cholesterol Peripheral protein Transmembrane proteins Cytoplasm Filaments of cytoskeleton 1972, S.J. Singer & G. Nicolson proposed Fluid Mosaic Model Phosphate Phospholipids Phosphate head hydrophilic Fatty acid tails “attracted to water” Fatty acid hydrophobic Arranged as a bilayer “repelled by water” Aaaah, one of those structure–function examples Arranged as a Phospholipid bilayer Serves as a cellular barrier / border sugar H2 O salt polar hydrophilic heads nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads waste lipids Cell membrane defines cell Cell membrane separates living cell from aqueous environment thin barrier = 8nm thick Controls traffic in & out of the cell allows some substances to cross more easily than others • hydrophobic (nonpolar) vs. hydrophilic (polar) Permeability to polar molecules? Membrane becomes semi-permeable via protein channels specific channels allow specific material across cell membrane inside cell NH3 H2 O salt aa sugar outside cell Cell membrane is more than lipids… Transmembrane proteins embedded in phospholipid bilayer create semi-permeabe channels lipid bilayer membrane protein channels in lipid bilyer membrane Why are proteins the perfect molecule to build structures in the cell membrane? 2007-2008 Proteins domains anchor molecule Within membrane Polar areas of protein nonpolar amino acids • hydrophobic • anchors protein into membrane On outer surfaces of membrane in fluid polar amino acids • hydrophilic • extend into extracellular fluid & into cytosol Nonpolar areas of protein + H H+ Retinal chromophore Examples NH2 aquaporin = water channel in bacteria H2 O Porin monomer b-pleated sheets Bacterial outer membrane Nonpolar (hydrophobic) a-helices in the cell membrane COOH H+ + H Cytoplasm proton pump channel in photosynthetic bacteria H2 O function through conformational change = protein changes shape Many Functions of Membrane Proteins “Channel” Outside Plasma membrane Inside Transporter Enzyme activity Cell surface receptor Cell surface identity marker Cell adhesion Attachment to the cytoskeleton “Antigen” Membrane Proteins Proteins determine membrane’s specific functions cell membrane & organelle membranes each have unique collections of proteins Classes of membrane proteins: peripheral proteins • loosely bound to surface of membrane • ex: cell surface identity marker (antigens) integral proteins • penetrate lipid bilayer, usually across whole membrane • transmembrane protein • ex: transport proteins – channels, permeases (pumps) Membrane carbohydrates Play a key role in cell-cell recognition ability of a cell to distinguish one cell from another • antigens important in organ & tissue development basis for rejection of foreign cells by immune system