Ap bio ch 5 ppt Cell Membranes

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Ap bio ch 5 ppt Cell Membranes

  1. 1. Ch 5 Membrane Structure & Function• Structure• Traffic across – Passive transport • Diffusion • Osmosis • Facilitated diffusion – Active transport – Endo & exocytosis
  2. 2. Functions of Membrane Proteins• Transport• Enzyme activity• Signal transduction• Intercellular joining• Cell to cell recognition• Attachment to cytoskeleton
  3. 3. Structure of Membrane• Phospholipids & proteins• Fluid mosaic model• Factors that affect fluidity: – Fatty acid type – Temp• Types of proteins – Integral – Peripheral
  4. 4. Traffic Across Mem• Selective permeability (ease & rate) depend on 2 things: 1. discriminating barrier of lipid bilayer – Impermeable to larger polar & ions – Perm to nonpolar – How about water?2. Transport proteins
  5. 5. Traffic Across MembraneRemember diffusion…
  6. 6. Osmosis• Why important?• Relative terms used to compare concentration of inside vs outside of cells – Hypertonic – Hypotonic – Isotonic• Water always moves toward hypertonic• Solutes move from high to low concentration.
  7. 7. Animal cells in hypotonic & hypertonic solutions
  8. 8. Cells in a hypotonic solution gain water & swell; possiblyburst if no cell wall.Cells in a hypertonic solution lose water & shrink.Cells in an isotonic solution have no net gain or loss ofwater.
  9. 9. Osmoregulation – control of water balance• Ex of how orgs stabilize water loss & uptake: – Freshwater paramecium
  10. 10. OsmosisEx of how orgsstabilize waterloss & uptake:Marine org - shark
  11. 11. Passive transport• Diffusion across a membrane• Requires no energy b/c molecules moving down concentration gradient (H to L)• 3 types – Diffusion – Osmosis – Facilitated diffusion
  12. 12. • Diffusion of solutes across membrane w/ Facilitated Diffusion help of proteins – Large polar or ions – proteins • Specific • Can be sat • Can be inhibited – Protein transports solute Cystic Fibrosis by • Changing shape • Selective channels
  13. 13. Cystic FibrosisCause:Humans have a gene encoded in their DNA which manufactures a special protein known as CFTR, Cystic Fibrosis Transmembrane Conductance Regulator. This protein controls the flow of chloride ions across the cell membrane.
  14. 14. The pumping of solutes against Active Transport their gradient (L to H)• Nonspontaneous• Requires energy (usually ATP)• Maintains steep ionic gradients (potential energy)• Ex: Na/K pump
  15. 15. Active transport
  16. 16. ActivetransportIon pumps – pump ions across membrane – generate voltage across mem – Electrochemical gradient – combo of concentration gradient & electrical gradient – Na/K pump is ex
  17. 17. Endocytosis & Exocytosis• Methods for very large molecules & particles to get into & out of the cell• Requires energy b/c requires movement of the plasma membrane. http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf Animation, baby!
  18. 18. Endocytosis & Exocytosis Exocytosis EndocytosisDefinition Exporting Importing of macromolecules by macromolecules by fusion of vesicles to pm forming vesicles with pmVesicles come Budded from ER or Pm & sinks inward &from Golgi pinches off into cytoplasmUsed to Secrete products - Incorporate insulin extracellular large substances
  19. 19. Endocytosis3 types:• Phagocytosis – cell “eating” solid particles (uses pseudopodia)• Pinocytosis – cell “drinking” fluid droplets• Receptor mediated endocytosis – importing specific macromolecules
  20. 20. Since cells can’t continue to grow larger,they must split, or divide at some point.
  21. 21. Cell Cycle2 parts:• Interphase – period of growth & DNA synthesis (copying)• Mitotic phase – period of cell division (1 cell divides into 2 cells) I love cells, baby!
  22. 22. Interphase – time of cell growth & copying of DNA3 phases of interphase:• G1 – growing & ribosomes making proteins• S – synthesis (or copying) of DNA (sister chromatids formed)• G2 – growing & getting ready to divide
  23. 23. Cells spend most of their time in interphase. DNA is in chromatin (stringy) form.
  24. 24. Mitotic Phase – time of cell divisionConsists of 2 main phases:1. Mitosis – division of nucleus2. Cytokinesis – division of cytoplasm
  25. 25. Sister Chromatids• Identical copies of chromosomes attached by a centromere.
  26. 26. Mitosis4 phases:• Prophase• Metaphase• Anaphase• Telophase http://www.cellsalive.com/mitosis.htm
  27. 27. Prophase• DNA condenses into chromosomes• Nuclear membrane disappears• Centrioles move toward poles• Spindle fibers form & attach to chromosomes
  28. 28. Metaphase• Sister chromatids lined up on metaphase plate with spindle fibers attached to them.
  29. 29. Anaphase• Sister chromatids get pulled apart to poles as spindle fibers shorten.
  30. 30. Telophase• New nuclear membrane forms around chromosomes at each pole• Chromosomes “unpack” into chromatin• Cell membrane begins to pinch in (animals cells) or cell plate develops (plant cells)
  31. 31. Cytokinesis – division of the cytoplasm Cell plate Cleavage furrow
  32. 32. Control of the Cell Cycle• Enzymes control cell cycle so cells divide at the right times• Cancer – uncontrolled cell division caused by a change in the DNA that codes for the making of the control enzymes
  33. 33. Cell Cycle Control• http://wps.prenhall.com/esm_freeman_biosci _1/7/1948/498717.cw/index.html
  34. 34. Internal Vs external signals• Internal – the checkpoints• External – growth factors, density dependent inhibition, anchorage dependence
  35. 35. cancer• Tumor• Begign• Malignant• Metastasis• Radiation & chemo
  36. 36. Cancer• Forms tumors & can spread through body - metastasize
  37. 37. Causes of Cancer• Environmental factors• UV radiation from sun• Tobacco• Viral infections• Genetic
  38. 38. How to prevent cancer:• Low fat, high fiber diet• Vitamins• Exercise• Don’t smoke• Use sunscreen• Regular doctor appointments
  39. 39. Removal of colon polyps• http://www.gihealth.com/flashvideo/flash.html
  40. 40. Review of the cell cycle• http://www.c ellsalive.co m/mitosis.ht m

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