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AP Biology

AP Biology . Chapter 6 and 7 Tour of the Cell Membrane Transport. Eukaryotic cell’s genetic instructions. Nucleus Nuclear envelope Nuclear lamina Chromosomes Nucleolus . Eukaryotic cell ribosomes. Ribosomes Free ribosomes Bound ribosomes. Endomembrane system. Nuclear envelope ER

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AP Biology

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  1. AP Biology • Chapter 6 and 7 • Tour of the Cell • Membrane Transport

  2. Eukaryotic cell’s genetic instructions • Nucleus • Nuclear envelope • Nuclear lamina • Chromosomes • Nucleolus

  3. Eukaryotic cell ribosomes • Ribosomes • Free ribosomes • Bound ribosomes

  4. Endomembrane system • Nuclear envelope • ER • Golgi apparatus • Lysosomes • Plasma membrane • Vesicles • Vacuoles

  5. Endosymbiosis Theory

  6. Mitochondria • Mitochondria • Cristae • Mitochondrial matrix

  7. Chloroplasts • Thylakoids • Granum • Stroma • plastids

  8. Peroxisomes

  9. Cytoskeleton • Network of fibers extending throughout the cytoplasm • Roles of cytoskeleton • Mechanical support to cell shape • Cell motility (movement) using motor proteins

  10. Cell junctions • Tight junctions- plasma membrane of other cells form a seal which prevents leakage

  11. Cell Junction • Desmosomes (anchoring) Fasten cells together into strong sheets

  12. Cell Junction • Gap Junction- provide cannels so cells can communicate with each other, and molecules can pass to and from

  13. AP Biology- Quiz today • Finishing extracellular components

  14. Cell wall parts of plant • Cell wall- protects and maintains shape • Primary cell wall- thin flexible wall (young plant) • Secondary cell wall- hardened structure between the plasma membrane and primary wall • Middle lamella- Thin layer with sticky polysaccharides (pectins) glues cells together • Plasmodesmata- communicating channel between plant cells

  15. Chapter 7- Membranes • The plasma membrane separates the living cell from its surroundings • Selectively permeable: some substances cross more easily than others • Membrane encloses a solution different from the surrounding solution

  16. Phospholipid bilayer • Contains: lipids, proteins, and carbohydrates • Most abundant lipid: phospholipid • Amphipathic molecule: hydrophilic and hydrophobic regions

  17. Phospholipid Bilayer • Fluid mosaic model: the membrane is a fluid structure with various proteins embedded in or attached to the double layer

  18. Phospholipid bilayer • Not all membranes are like • Membranes with different functions differ in chemical composition and structure • Measurements showed that membrane proteins are not very soluble in water

  19. Phospholipid bilayer • Freeze fracture technique • Splits a membrane along the middle of the phospholipid bilayer • Found that: membranes are more mosaic than fluid, lipids appear to form defined regions

  20. Phospholipid Bilayer • Membrane molecules are held in place by relatively weak interactions • Most lipids and some proteins drift laterally in the plane of the membrane but rarely flip-flop from one phospholipid layer to the other

  21. Phospholipid bilayer • Membrane fluidity is influenced by temperature: • As temperature cools, membranes switch from a fluid state to a solid state • Phospholipids pack together more closely

  22. Phospholipid bilayer • Steroid cholesterol is wedged between phospholipid molecules in the plasma membrane of animal cells • Warm temp: restrains movement (reduces fluidity) • Cold temp: maintains fluidity by preventing tight packing • Fluidity buffer

  23. Proteins determine membrane’s function • Two major populations of membrane proteins: integral and peripheral

  24. Membrane Proteins • Integral- • Embedded in the bilayer • Penetrate hydrophobic interior of bilayer • Peripheral- • Not embedded in the bilayer • Loosely bound to surface of membrane

  25. Major functions of membrane proteins • Transport • Enzymatic activity • Signal transduction (relaying messages) • Cell-cell recognition • Intercellular joining • Attachment to cytoskeleton

  26. Cell to cell recognition- ability of a cell to distinguish one type of neighboring cell from another • Membrane carbohydrates may be bonded to lipids or proteins making glycolipids or glycoproteins respectively

  27. Selective permeability and structure: • Small molecules and ions move across the plasma membrane in both directions Example: • sugar, amino acids and other nutrients enter a muscle cell and metabolic waste leave • The muscle cell takes in oxygen and expels carbon dioxide • Muscle also regulates the concentrations of inorganic ions, such as Na, K, Ca, Cl by shuttling them one way or the other across the membrane

  28. Movement of molecule depends on the interaction of the molecule with the hydrophobic interior of membrane • Nonpolar molecules can dissolve in the lipid bilayer easily • Polar molecules and water extremely small can cross bilayer slowly • Passage of water occurs via aquaporins • Carrier proteins- bind to molecules and change shape to shuttle them across membrane

  29. Water potential • A property predicting the direction in which water will flow • Formula: • Ψ = ΨS + ΨP

  30. Water Potential • ΨS = -iCRT • i = ionization constant (1 for sucrose) • C = osmotic molar concentration • R = Pressure constant (R= 0.0831 liter bars/mole °Kelvin • T = temperature

  31. Calculations: • Calculate the osmotic potential using the following data. Answer should be in bars. • C = 0.32 • T =21 °C *must convert to Kelvin

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