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Cell Membrane Structure & Function Review Session

Learn about the fluid mosaic model of the cell membrane, its components, and functions. Practice labeling, drawing diagrams, and understanding the roles of key proteins. Enhance your knowledge for upcoming tests and assignments.

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Cell Membrane Structure & Function Review Session

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  1. Grade breakdowns—Period 5 • A=4 • B=5 • C=13 • F=3 (Mandatory tutoring)

  2. Build a cell membrane • Aka lipid bilayer • Aka plasma membrane LABEL 5 components Label outside and inside cell

  3. 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

  4. 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

  5. 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

  6. Ch.7~MembraneStructure&Function Fluid mosaic model

  7. 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

  8. Membrane structure, I • Selective permeability • Amphipathic~ hydrophobic & hydrophilic regions • 1935 Davson Danielli sandwich model • Singer-Nicolson: 1972 fluid mosaic model

  9. 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!

  10. 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

  11. 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

  12. 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

  13. 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)

  14. 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

  15. Cell membrane is more than lipids… • Transmembrane proteins embedded in phospholipid bilayer • create semi-permeabe channels lipid bilayer membrane protein channelsin lipid bilyer membrane

  16. Why areproteins the perfect molecule to build structures in the cell membrane?

  17. 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

  18. 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

  19. Many Functions of Membrane Proteins “Channel” Outside Plasma membrane Inside Transporter Enzymeactivity Cell surfacereceptor “Antigen” Cell adhesion Cell surface identity marker Attachment to thecytoskeleton

  20. 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)

  21. 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

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