Cell Parts


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Cell Parts

  1. 1. Outer protection Cell control center Energy center Cell processing Storage and Waste Cell divisionCell Parts
  2. 2. Organelle  Organs are specialized structures in the body that perform specific life processes  Organelles are specialized structures inside the cell that perform specific cellular processes  Most organelles are surrounded by a membrane
  3. 3. Cell ProcessesAll cells have to perform the same basicactivities to stay alive:  Use energy  Store materials  Absorb materials  Transport substances  Eliminate waste  Reproduce
  4. 4. Cell Fractionation A method of separating cell parts to study their function Homogenization: disruption of cell membrane without damaging organelle Centrifuge: instrument that spins at high speeds to separate contents by density
  5. 5. http://richmondschoolbiology.files.wordpress.com/2008/09/cell-fractionation-diagram.jpg?w=652&h=450
  6. 6. Cell Fractionation http://www.freewebs.com/ltaing/chpt7.3Cellfractionation.gif
  7. 7. Steps to Cell Fractionation1. Homogenize2. Centrifuge  Pellet: larger, more dense components  Supernatant: lighter, suspended in liquid above the pellet3. Decant supernatant4. Repeat centrifugation at higher speeds to separate into smaller components
  8. 8. Topics Membranes & contents  Plasma membrane, cell wall, cytoplasm Nucleus & contents  Nucleus, nuclear envelope, nucleolus, ribosome Endomembrane System  ER, Golgi body, lysosome, vacuole, vesicles Organelles in metabolism  Mitochondria, chloroplast, peroxisome Cytoskeleton  Microfilament, intermediate filament, microtubule
  9. 9. Cell Membrane  All cells are surrounded by a flexible membrane  Also known as the plasma membrane  Controls exchange of material between interior of the cell and the external environment  Protection
  10. 10. Plasma Membrane Structure Cell membrane made of phospholipid Phospholipids also form the membrane around organelles
  11. 11. Phospholipid Bilayer Bilayer = 2 layers Each layer is called a leaflet and composed of phospholipids
  12. 12. Phospholipid Bilayer Phospholipid arranged so that hydrophobic tails do not face water Water is on the intracellular and extracellular side Hydrophobic tails face inwards forming a hydrophobic core Hydrophilic heads face outwards
  13. 13. Fluid Mosaic Model Model developed by Singer and Nicolson (1972) to understand membrane structure Fluid implies movement on membrane Mosaic implies that the membrane consists of many different molecules
  14. 14. Membrane FluidityMembrane fluidity is affected by: Saturation of fatty acid  Double bonds bends fatty acid chains preventing phospholipids from tight packing Hydrophobic restrictions  Lateral movement: across same leaflet  Flip-flop movement is rare Cholesterol and temperature
  15. 15. Properties of Cholesterol Large molecular size  Can interrupt intermolecular forces of attraction Nonpolar  Stabilizes hydrophobic interactions
  16. 16. Properties of Cholesterol Explain which property of cholesterol plays a more significant role at:  Low temperature  High temperature Why is this advantageous for a cell?
  17. 17. Mosaic: Membrane Composition Membrane Proteins  Integral  Peripheral Carbohydrates
  18. 18. Integral Membrane Proteins Embedded in the membrane and spans the entire width of the bilayer Function: transport  Assist in movement of molecules into and out of cell Classification  type of transport: active or passive  direction of transport: Uniport, symport, antiport (more about this in the Membrane Transport lesson)
  19. 19. Peripheral Membrane Proteins Bound non-covalently to either surface of the membrane Function  Extracellular side: communication  Intracellular side: structural support
  20. 20. Extracellular Peripheral Protein Receptor and recognition proteins Located on outer leaflet and surface Example: antigens, glycoproteins
  21. 21. Intracellular Peripheral Protein Cytoskeletal protein Located on inner membrane surface Attached to cytoskeleton of cell Immobilized (anchored) on membrane
  22. 22. Carbohydrates Glycoprotein = carbohydrate + protein Glycolipid = carbohydate + lipid (phospholipid) Extracellular side Function of cell surface carbohydrates:  identifies the cell (like a name) helping other cells recognize it  acts as a signal for communication
  23. 23. Asymmetry Each leaflet has a different composition Leaflet facing the intracellular side has different components compared to the extracellular side Restrictions in the flip-flop motion help to maintain this asymmetry
  24. 24. Phospholipid Bilayer
  25. 25. Phospholipid Bilayer
  26. 26. Cell Wall  Found outside of the cell membrane in plant and prokaroytes  Rigid but porous  Gives shape and support  Provide protection from injury
  27. 27. Cell Wall Structure Basic composition like steel-reinforced concrete: microfibrils made of cellulose embedded in a matrix of other polysaccharides and proteins
  28. 28. Cell Wall Structure Primary cell wall: in young plants, thin and flexible Middle lamella: thin layer of pectin (sticky) Secondary cell wall: in mature plants, between primary cell wall and cell membrane Plasmodesmata: perforations in the cell wall that connect adjacent cells
  29. 29. Cytoplasm  Also known as the cytosol  Mostly made of water  Can range from a liquid to a jelly-like substance  Contains dissolved substances  Organelles are suspended in the cytoplasm (but are anchored by cytoskeleton and not freely floating)
  30. 30. Nucleus  Control centre of the cell  Contains genetic information (e.g. chromosomes)  Contains nucleolus  Surrounded by a nuclear membrane  Nuclear membrane is double layered and has pores
  31. 31. Nucleolus  Darker area in the nucleus  Synthesis of rRNA (ribosomal RNA)  Assembly of rRNA with protein imported from the cytoplasm to form the large and small ribosomal subunits
  32. 32. Ribosome Structure RNA protein complex  2/3 RNA (double stranded coils in turquoise, grey, orange, indigo)  1/3 protein (small coiled alpha helices in violet and navy blue) http://rna.ucsc.edu/rnacenter/images/70s_atrna.jpg
  33. 33. Ribosome Structure  2 subunits:  large (turquoise colour)  small (lime green colour) http://www.ks.uiuc.edu/Gallery/Science/translation_proteins/tn/ribosome_ao_small_st.jpg.html
  34. 34. Ribosomes  Made in nucleolus  Can be bound to the rough endoplasmic reticulum or float freely in cytoplasm  Function to catalyze the reactions of protein synthesis
  35. 35. Endomembrane SystemOrganelles oftheendomembranesystem are direct through:related physical contact transfer of membrane segments as vesicles http://www.science-art.com/gallery/52/52_10202008105023.jpg
  36. 36.  Nuclear envelope Endomembrane System Rough and Smooth ER Golgi Body Lysosome Vacuole Vesicles http://bioserv.fiu.edu/~walterm/fallspring/cell_components/cell_talk_files/image010.jpg
  37. 37. Endoplasmic Reticulum Structure  Cisternae: network of flattened, interconnected membrane sacs (tubes and pockets)  Continuous with the nuclear envelope
  38. 38. Endoplasmic Reticulum Types Two types of ER are distinct but connected: rough and smooth
  39. 39. Rough Endoplasmic Reticulum Contains ribosomes bound to its membrane surface Produces integral and secretory proteins:  Integral proteins are embedded in the ER membrane and will end up on the plasma membrane  Secretory proteins are housed in the cisternal space of the ER and will be secreted by exocytosis  Both protein types will be delivered to the cell surface via transport vesicles Note: Free ribosomes produce cytosolic proteins
  40. 40. Smooth Endoplasmic Reticulum No ribosomes on its membrane surface Site for lipid synthesis
  41. 41. Golgi Body Structure  Also consists of cisternae: flattened, stacked, interconnected membrane sacs (similar to ER)  Located near ER  Also known as the Golgi apparatus
  42. 42. Golgi Body Function Modifies proteins and lipids Process materials to be removed from the cell Directs secretion:  Make and secrete mucus  Packages products into vesicles for transport  Sorts and targets vesicle to various parts of the cell
  43. 43. Golgi Body  Golgi is polar: cis and trans poles  Cis face  “receiving” side  Located near the ER  Transport vesicles bud from ER and add its membrane and content of the lumen to Golgi http://4.bp.blogspot.com/_rBYpndaJ_ak/S-sxGmLUOuI/AAAAAAAAAGM/oKWwbrO41-U/s1600/Golgi+apparatus.gif
  44. 44. Golgi Body Trans face  “shipping” side  Vesicles bud from Golgi to various locations Targets of vesicles:  Other organelles  Cytoplasm  Plasma membrane surface  Export - outside cell http://4.bp.blogspot.com/_rBYpndaJ_ak/S-sxGmLUOuI/AAAAAAAAAGM/oKWwbrO41-U/s1600/Golgi+apparatus.gif
  45. 45. Lysosome Membrane bound sac of hydrolytic enzymes Enzyme and lysosomal membrane made by RER and transferred to Golgi http://www.daviddarling.info/images/lysosome.gif
  46. 46. Lysosome Enzymes work best at pH 5 Maintains acidic pH by pumping H+ into the lumen Why would a cell want lysosomal enzymes to function at a pH that is different from the cytosol (neutral pH)? http://www.daviddarling.info/images/lysosome.gif
  47. 47. Lysosome FunctionInvolved as one of the steps after phagocytosis(see membrane transport lesson)  lysosome fuse with food vacuole to digest food (acts similarly to stomach in animals)  Lysosome fuses with phagosome (vesicle formed from phagocytosis) to breakdown microorganisms (e.g. WBC digesting bacteria) http://kvhs.nbed.nb.ca/gallant/biology/lysosome.jpg
  48. 48. Lysosome Function  Autophagy: lysosome recycles cell’s own organic material  Important in development of multicellular organisms  Tadpole to frog: destroy cells of tail  Human embryos: destroy webbing between fingers http://kvhs.nbed.nb.ca/gallant/biology/lysosome.jpg
  49. 49. Vacuole  Function: Storage of food, water, waste  Fluid-filled membrane bound sac surrounded  Similar to vesicles but tend to be larger  Derived from the ER and Golgi  In animal cells: many small vacuoles  In plant cells: one large central vacuole
  50. 50. Types of Vacuoles Central vacuole  in plants  maintain internal fluid pressure (turgor) which helps gives plants structure and strength
  51. 51. Types of VacuolesFood vacuole formed by phagocytosis fuses with a lysosome to digest food and invaders
  52. 52. Types of VacuolesContractile vacuole in freshwater protists (e.g. paramecium) pump excess water out of the cell http://bio1151.nicerweb.com/Locked/media/ch07/contractile.html
  53. 53. Endomembrane System Can you describe what is happening at each phase? http://www.yellowtang.org/images/how_endomembrane_sy_c_la_784.jpg
  54. 54. Organelles in Metabolic Function Mitochondria Chloroplast Peroxisome
  55. 55. Mitochondria Structure  Surrounded by a double membrane  Inner membrane is folded to increase the surface area  Reactions occur on the inner membrane surface
  56. 56. Mitochondria Function  Produces energy through a process called cellular respiration  Reaction involves converting energy from food (e.g. sugars) to cellular energy  Process that occurs inside the mitochondria is aerobic (requires oxygen) glucose + O2 CO2 + H2O + energy
  57. 57. Mitochondria  Cells that are very active (e.g. muscle cells) contain many mitochondria  Cells that are fairly inactive (e.g. fat cells) only have a few mitochondria
  58. 58. Chloroplast Structure  Surrounded by a double membrane  Contain chlorophyll, a pigment that gives plants their green colour
  59. 59. Chloroplast Structure  Thyakoid: flattened discs (some are interconnected) containing chlorophyll; where light reactionsX of photosynthesis take place  Granum (grana): Stack(s) of thylakoid  Stroma: Space inside chloroplast
  60. 60. Chloroplast Function  Site for starch (a type of sugar) storage  Site for photosynthesis  Reaction involves trapping light energy to create food in the form of sugars  Starting substances are carbon dioxide and water CO2 + H2O + energy  O2 + glucose
  61. 61. Perioxisome Function Contain enzymes that oxidize organic molecules by transferring hydrogen from substrate to oxygen Process is useful for:  breaking down fatty acids  detoxifying alcohol and other harmful compounds Produces hydrogen peroxide (H2O2) as a byproduct  Hydrogen peroxide is toxic to the cell  Contains another enzyme (catalase) that decomposes hydrogen peroxide to water
  62. 62. Peroxisome Structure Bound by a single membrane Spherical with a distinct crystalline core that is a dense collection of enzymes Often located near mitochondria and chloroplast http://www.daviddarling.info/images/peroxisome.jpg
  63. 63. Cytoskeleton  A network of fibers extending throughout the cytoplasm  Dynamic: can be quickly dismantled and reassembled in a new location
  64. 64. CytoskeletonComponent Microfilament: actin Intermediate filament Microtubules: tubulin http://www.sciencephoto.com/image/395086/530wm/C0097404-Cytoskeleton_components,_artwork-SPL.jpg
  65. 65. Cytoskeleton Component http://www.sciencephoto.com/image/395087/530wm/C0097406-Cytoskeleton_components,_diagram-SPL.jpg
  66. 66. Cytoskeleton ComponentType Microfilament Intermediate Microtubule FilamentStructureDiameterIntracellularFunctionOtherFunction http://www.sciencephoto.com/image/395087/530wm/C0097406-Cytoskeleton_components,_diagram-SPL.jpg
  67. 67. Cytoskeleton ComponentType Microfilament Intermediate Microtubule FilamentStructure 2 intertwined Fibrous Hollow tube strands of protein of 13 tubulin actin supercoiled columnsDiameter 7 nm 8-12 nm 25 nmIntracellular Changes in Anchorage OrganelleFunction cell shape of organelles & (e.g. furrow) chromosome movementOther Muscle Cell motility http://www.sciencephoto.com/image/395087/530wm/C0097406-Cytoskeleton_components,_diagram-SPL.jpg
  68. 68. Cytoskeleton Fluorescent light micrograph of fibroblast cells Nuclei (green) Cytoskeleton:  actin filaments (purple)  microtubules (yellow) http://www.sciencephoto.com/media/316728/enlarge
  69. 69. Cytoskeleton Cellular FunctionSummary  Microfilament: mechanical support to maintain cell shape  Intermediate filament: anchorage for organelles and cytosolic enzymes  Microtubule: path for organelle, vesicles & chromosomes to travel; originate from centrosome
  70. 70. Centrosome  A region near the nucleus where microtubules grow out from  Involved in organizing spindle fibers during cell division  In animal cells, a pair of centrioles exist within this region
  71. 71. Centrioles Exists as pairs in animal cells only Composed of 9 sets of triplet microtubules arranged in a ring Help organize spindle fibers during cell division
  72. 72. HW Question1. Give 2 reasons why it is better for an animal cell to have organelles rather than to perform all its cellular functions in the cytoplasm. Provide a specific example for your reasons. [3 marks]2. If you were given an illustration of a cross-section of a cell membrane, describe two things that would help you identify the side that faces the outside environment. [2 marks]3. Describe the flow of molecules through the endomembrane system. [5 marks]
  73. 73. Summary of DifferencesFunction Animal Plant Outerprotection Energy centre StorageCentrioles
  74. 74. Summary of DifferencesFunction Animal Plant Outer Plasma membrane Plasma membraneprotection Cell wall Energy Mitochondria Mitochondria centre Chloroplast Many small One large central Storage vacuoles vacuoleCentrioles Present Absent
  75. 75. Summary by Cellular Processes Function Organelle & cell partsOuter protectionCell control centreEnergy centreCell processingStorage and wasteCell division
  76. 76. Summary by Cellular Processes Function Organelle & cell partsOuter protection Cell wall, Plasma membraneCell control centre Nucleus, nucleolusEnergy centre Mitochondria, Chloroplast Endoplasmic reticulum,Cell processing ribosomes, Golgi bodyStorage and waste Vacuole, cytoplasm, chloroplastCell division Centrioles