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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:
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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
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 ...? Danish Review • Make 4 higher level questions from • Ecology • Evolution • Chemistry • Cells
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 • Draw a membrane and label 5 components • 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!
Glycoprotein Glycolipid Transmembrane proteins Peripheral protein Filaments ofcytoskeleton Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Extracellular fluid Phospholipids Cholesterol Cytoplasm 1972, S.J. Singer & G. Nicolson proposed Fluid Mosaic Model
Phospholipids Phosphate “attracted to water” • Phosphate head • hydrophilic • Fatty acid tails • hydrophobic • Arranged as a bilayer Fatty acid “repelled by water” Aaaah, one of thosestructure–function examples
Arranged as a Phospholipid bilayer sugar H2O salt • Serves as a cellular barrier / border polar hydrophilic heads nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads lipids waste
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 H2O aa sugar salt outside cell NH3
Cell membrane is more than lipids… • Transmembrane proteins embedded in phospholipid bilayer • create semi-permeabe channels lipid bilayer membrane protein channelsin lipid bilyer membrane
Why areproteins the perfect molecule to build structures in the cell membrane?
Proteins domains anchor molecule Polar areas of protein • Within membrane • 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
Porin monomer H+ Retinal chromophore b-pleated sheets NH2 Bacterial outer membrane Nonpolar (hydrophobic) a-helices in the cell membrane COOH Cytoplasm H+ H+ Examples aquaporin = water channel in bacteria H2O H+ proton pump channel in photosynthetic bacteria function through conformational change = protein changes shape H2O
Many Functions of Membrane Proteins “Channel” Outside Plasma membrane Inside Transporter Enzymeactivity Cell surfacereceptor “Antigen” Cell adhesion Cell surface identity marker Attachment to thecytoskeleton
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