BIOL 108 Chp 3 - Cells


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BIOL 108 Chp 3 - Cells

  1. 1. Chapter 3CellsBIOL 108 Rob Swatski Assoc Prof BiologyIntro to Bio Sci HACC-York 1
  2. 2. Learning Goals Describe how Describe cells are Describe Describe the Describe nine several ways connectedwhat a cell is structure and important in which and how and the two functions of landmarks in molecules theygeneral types cell eukaryotic move across communicate of cells. membranes. cells. membranes. with each other. 2
  3. 3. 3.1 All organisms are made of cells. 3
  4. 4. Cell: the smallest unit of lifethat can functionindependently and performall the necessary functionsof life, includingreproducing itself. 4
  5. 5. Cells Robert Hooke, a British scientist, mid-1600s 3-D structures, likefluid-filled balloons, in which many of the essential chemical reactions of life take place Nearly all cells contain DNA(deoxyribonucleic acid). 5
  6. 6. How to See a Cell 6
  7. 7. Cell Theory 1. All living 2. All cells ariseorganisms are from other pre-made up of one existing cells. or more cells. 7
  8. 8. Take-Home Message 3.1 The most basic unit of any organism is the cell, the smallest unit of life that can function independently and perform all of the necessary functions of life, including reproducing itself. All living organisms are made up of one or more cells and all cells arise from other pre-existing cells. 8
  9. 9. 3.2 Prokaryotic cellsare structurally simple, but there are many types of them. 9
  10. 10. Every cell on earth falls into one of two basic categories:Prokaryotic cell Eukaryotic cell 10
  11. 11. Prokaryotic Eukaryotic Cell Cell Does not have a Has a nucleus nucleus Its DNA simply The nucleus resides in the contains the cell’s middle of the cell DNA Prokaryotes Eukaryotes 11
  12. 12. 12
  13. 13. Take-Home Message 3.2 Prokaryotes, which have no Every cell on earth is either nucleus, were the first cellsa eukaryote or a prokaryote. on earth. Prokaryotes include the bacteria and archaea and, They are all single-celled as a group, are organisms. characterized by tremendous metabolic diversity. 13
  14. 14. 3.3 Eukaryotic cells have compartments with specialized functions. 14
  15. 15. 15
  16. 16. 16
  17. 17. Endosymbiosis Theory Developed to explain thepresence of two organellesin eukaryotes, chloroplasts in plants and algae, andmitochondria in plants and animals. 17
  18. 18. Humans, deep down, may be part bacteria. How can that be? 18
  19. 19. 19
  20. 20. Take-Home Message 3.3 Eukaryotes are single-celled or multicellular organisms whose cells have a nucleus that contain linear strands of genetic material. They also commonly have organelles throughout their cytoplasm, which may have originated evolutionarily through endosymbiosis or invagination. 20
  21. 21. 3.4–3.7Cell membranesare gatekeepers. 21
  22. 22. 22
  23. 23. 3-4. Every cell is bordered by a plasma membrane. 23
  24. 24. Permeable 24
  25. 25. Impermeable 25
  26. 26. Semipermeable 26
  27. 27. Functions of the Plasma Membrane Regulate Take in Build & Regulate flow of Dispose of food & export heat materials wastesnutrients molecules exchange in & out of cell 27
  28. 28. 28
  29. 29. Take-Home Message 3.4 Every cell of every livingorganism is enclosed by a plasma membrane, a two-layered membrane that holds the contents of a cell in place andregulates what enters and leaves the cell. 29
  30. 30. 3.5 Moleculesembeddedwithin theplasmamembrane helpit perform itsfunctions. 30
  31. 31. What determines whether a protein resides on the surface or extends through the bilayer? 31
  32. 32. There are four primary types of membrane proteins, each of which performs a different function. 32
  33. 33. The Plasma Membrane“Fluid Mosaic” Proteins Short, branched carbohydrate chains Cholesterol 33
  34. 34. Take-Home Message 3.5 Proteins found in theThe plasma membrane is a plasma membrane enable it fluid mosaic of proteins, to carry out most of itslipids, and carbohydrates. gatekeeping functions. The proteins function asreceptors, help molecules Carbohydrates and plasma gain entry into and out of proteins identify the cell to the cell, and catalyze other cells.reactions on the inner and outer cell surfaces. Phospholipids make up the majority of plasma membranes, while cholesterol influences membrane fluidity. 34
  35. 35. 3.6 Faulty membranes can cause disease. 35
  36. 36. Why do “beta blockers” reduce anxiety? 36
  37. 37. Take-Home Message 3.6Normal cell functioning can be disrupted when cell Such malfunctions can membranes—particularly cause health problems, such the proteins embedded as cystic fibrosis. within them—do not function properly. But disruptions can also have beneficial therapeutic effects, such as in the treatments of high blood pressure and anxiety. 37
  38. 38. 3.7 Membrane surfaces have a “fingerprint” that identifies the cell.Cells with an improper fingerprint are recognized as foreign and are attacked byyour body’s defenses. 38
  39. 39. 39
  40. 40. Why is it extremely unlikely that a person will catch HIV fromcasual contact—such asshaking hands—with an infected individual? 40
  41. 41. 41
  42. 42. Take-Home Message 3.7 Every cell in your body has a “fingerprint” made from a variety of molecules on the outside-facing surface of the cell membrane. This molecular fingerprint is key to the function of your immune system. 42
  43. 43. 3.8–3.11Molecules moveacross membranesin several ways. 43
  44. 44. 3.8 Passive transport is the spontaneous diffusion ofmolecules across a membrane. 44
  45. 45. PassiveTransportThe spontaneous diffusion ofmolecules across a membrane Two types of passive transport: Diffusion & Osmosis 45
  46. 46. 46
  47. 47. Facilitated Diffusion Most molecules can’t get through plasma membranes on their own Carrier molecules Transport proteins 47
  48. 48. Defects inTransport Proteins Can reduce or even bring facilitated diffusion to a complete stop Serious health consequences &cause many genetic diseases Cystinuria & kidney stones 48
  49. 49. Take-Home Message 3.8Cells must acquire necessary Cells must remove metabolic materials, such as food waste molecules andmolecules, from outside the molecules for use elsewhere in cell. the body. In passive transport – whichincludes simple and facilitated This generally occurs as diffusion and osmosis – the molecules move down their molecular movement occurs concentration gradient. spontaneously, without the input of energy. 49
  50. 50. 3.9 Osmosis is thepassive diffusion of water across a membrane. 50
  51. 51. 51
  52. 52. Tonicity The relativeconcentration of solutes outside of the cellrelative to inside the cell Hypertonic Hypotonic Isotonic 52
  53. 53. How Do Laxatives RelieveConstipation? Milk of magnesia & magnesium salts Water moves via osmosis from the cells into the intestines. 53
  54. 54. The Direction of Osmosis Determined only by a difference in total concentration of all the molecules dissolved in the water It does not matter what solutes they are. 54
  55. 55. Take-Home Message 3.9 The diffusion of water across a membrane is a special type of passive transport called osmosis. Water molecules move across the membrane until the concentration of water inside and outside of the cell is equalized. 55
  56. 56. 3.10 In active transport, cells use energy to move small molecules.Molecules can’t always move spontaneously and effortlessly in and out of cells. 56
  57. 57. ActiveTransportCells use energy to move small moleculesTwo types: Primary& Secondary active transport Differ only in the source of the fuel 57
  58. 58. Primary active transport:uses energy directly from ATP 58
  59. 59. Secondary ActiveTransport An indirect method many transporter proteins use for fueling their activities The transport protein simultaneously movesone molecule against its concentration gradient while letting another flow down itsconcentration gradient.No ATP is used directly. 59
  60. 60. Take-Home Message 3.10 Active transport is necessary if the moleculesIn active transport, moving to be moved are very large molecules across a or if they are being movedmembrane requires energy. against their concentration gradient. Proteins embedded within the plasma membrane act like motorized revolving doors to actively transport the molecules. 60
  61. 61. 3.11 Endocytosis and exocytosis are used for bulk transport of particles. Many molecules are just too big to get into a cell by passive or active transport. 61
  62. 62. Three Types of Endocytosis: Receptor-Phagocytosis Pinocytosis mediated endocytosis 62
  63. 63. 63
  64. 64. Pinocytosis: the process of cells taking in dissolved particles and liquid 64
  65. 65. 65
  66. 66. Faulty cell membranes are a primary cause of cardiovascular disease. What modification to them might be an effective treatment? 66
  67. 67. 67
  68. 68. 68
  69. 69. Take-Home Message 3.11 When molecules cannot get into a cell via diffusion or a pump(e.g., when the molecules are too Similarly, molecules can be big), cells can engulf the moved out of a cell via materials with their plasma exocytosis. membrane in a process called endocytosis. In both processes the plasma membrane moves to surround the molecule and forms a little vesicle that can be pinched off inside the cell or fuse with the plasma membrane and dump its contents outside of the cell. 69
  70. 70. 3.12Cells are connectedand communicatewith each other. 70
  71. 71. 3.12 Connections between cells hold them in place and enable them to communicate with each other.71
  72. 72. Tight Junctions form continuous, water-tight seals around cells and also anchor cells in place particularly important in the small intestine where digestion occurs 72
  73. 73. Desmosomes are like spot welds or rivets that fasten cells together into strong sheets function like Velcro: they hold cells together but are not water-tight foundin much of the tissue-lining cavities of animal bodies 73
  74. 74. Gap Junctionspores surrounded by special proteins that form open channels between two cellsGap junctions are an important mechanism for cell-to-cell communication. 74
  75. 75. How can a lack of communication between cells lead to cancer? Contact inhibition Tumors 75
  76. 76. Plasmodesmata Tube-likechannels connecting the cells to each other and enabling communication and transport between them Consider a plant as one big cell? 76
  77. 77. Take-Home Message 3.12In multicellular organisms, The connections can form amost cells are connected to water-tight seal between other cells. the cells (tight junctions)… …or can function like secret …can hold sheets of cells passageways between cells, together while allowing allowing the movement of fluid to pass between the cytoplasm, molecules, and cells (desmosomes)… other signals (gap junctions). Plasmodesmata in plants connect cells, enabling communication and transport between them. 77
  78. 78. 3.13–3.21Nine importantlandmarksdistinguisheukaryotic cells. 78
  79. 79. 3.13 Nucleus: the cell’s genetic control center. The nucleus is the largest & most prominent organelle in most eukaryotic cells. The nucleus has two primary functions: 1. Genetic control center & 2. Stores heredity information 79
  80. 80. Take-Home Message 3.13 It directs most cellular The nucleus is usually the activities by controllinglargest and most prominent which molecules are organelle in the eukaryotic produced and in what cell. quantity they are produced. The nucleus is also the storehouse for all hereditary information. 80
  81. 81. 3.14 Cytoplasmand cytoskeleton:the cell’s internalenvironment,physical support,and movement. 81
  82. 82. 82
  83. 83. Cilia and Flagellum 83
  84. 84. Take-Home Message 3.14 It consists of three types This inner scaffolding of of protein the cell, which is made fibers―microtubules, from proteins, is the intermediate filaments, cytoskeleton. and microfilaments. It gives cells some abilityIt gives animal cells shape to control their and support. movement. It serves as a series of tracks on which organelles and molecules are guided across and around the inside of the cell. 84
  85. 85. 3.15 Mitochondria:the cell’s energy converters 85
  86. 86. 86
  87. 87. Bag-within-a-Bag Structure:the intermembrane space and the matrix 87
  88. 88. Endosymbiosis Mitochondria may have existed as separate single- celled, bacteria-like organisms billions of years ago. Mitochondria have their own DNA! We all have more DNA from one parent than the other… Why? 88
  89. 89. Take-Home Message 3.15 In mitochondria, the energy contained within the chemical bonds of carbohydrate, fat, and protein molecules is converted into carbon dioxide, water, and ATP—the energy source for all cellular functions and activities. Mitochondria may have their evolutionary origins as symbiotic bacteria living within other cells. 89
  90. 90. 3.16 Lysosomes: the cell’s garbage disposals 90
  91. 91. LysosomesRound, membrane-enclosed, acid-filled vesicles that function as garbage disposals 91
  92. 92. Tay-Sachs DiseaseGenetic disordersimilar to a strike by trashcollectors… Why? 50 differentenzymes necessary Malfunctionssometimes occur 92
  93. 93. Take-Home Message 3.16 Lysosomes are round, membrane-enclosed, acid- filled vesicles that function as a cell’s garbage disposal. They are filled with about 50 different digestive enzymes and enable a cell to dismantle macromolecules, including disease-causing bacteria. 93
  94. 94. The Endomembrane System 94
  95. 95. 3.17 Endoplasmic reticulum: where cells build proteins and disarm toxins 95
  96. 96. 96
  97. 97. 97
  98. 98. Take-Home Message 3.17The production and modification of biological molecules within eukaryotic cells occurs in a In rough ER, proteins that will be system of organelles called the shipped elsewhere in the body endomembrane system, which are folded and packaged. includes the rough and smooth endoplasmic reticulum. In the smooth ER, lipids are synthesized and alcohol, antibiotics, and other drugs are detoxified. 98
  99. 99. 3.18 Golgi apparatus: Where the cell processes products for delivery throughout the body 99
  100. 100. 100
  101. 101. 101
  102. 102. Take-Home Message 3.18 The Golgi apparatus—another organelle within the endomembrane system—processes molecules synthesizedwithin a cell and packages those that are destined for use elsewhere in the body. 102
  103. 103. 3.19 The cellwall providesadditionalprotection andsupport forplant cells 103
  104. 104. Take-Home Message 3.19 It is made primarily from theThe cell wall is an organelle found carbohydrate cellulose and it in plants (and some other non- surrounds the plasma membrane animal organisms). of a plant cell.The cell wall confers tremendousstructural strength on plant cells, In plants, plasmodesmata gives plants increased water connect cells and enable resistance, and provides some communication and transportprotection from insects and other between them. animals that might eat them. 104
  105. 105. 3.20 Vacuoles:multipurposestorage sacs forcells105
  106. 106. Take-Home Message 3.20 In plants, vacuoles can Vacuoles also appear inoccupy most of the interior some other eukaryotic space of the cell. species. They function as storage space and play a role in nutrition, waste management, predator deterrence, reproduction, and physical support. 106
  107. 107. 3.21Chloroplasts:the plantcell’s powerplant 107
  108. 108. The stroma and interconnected little flattened sacs called thylakoids 108
  109. 109. EndosymbiosisTheory Revisited Chloroplasts resemble photosynthetic bacteria Circular DNA Double outer membrane 109
  110. 110. 110
  111. 111. 111
  112. 112. Take-Home Message 3.21 The chloroplast is an organelle in plants and algae in which photosynthesis occurs. Chloroplasts may have originally been bacteria that were engulfed by a predatory cell by endosymbiosis. 112