Ppt chapter 031

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Ppt chapter 031

  1. 1. Chapter 3Cells: The Living Units
  2. 2. Cell Theory• The cell is the basic structural and functional unit of life• Organisms depend on individual and collective activity of cells, dictated by subcellular structures• Continuity of life has a cellular basisCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  3. 3. Structure of a Generalized CellCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  4. 4. Plasma Membrane• Separates intracellular fluids from extracellular fluids• Plays a dynamic role in cellular activityCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  5. 5. Fluid Mosaic Model • Double bilayer of lipids with imbedded, dispersed proteins • Bilayer consists of phospholipids, glycolipids, cholesterol and proteins • Phospholipid bilayer has hydrophobic (in the middle) and hydrophilic (facing the outside) portions • Glycolipids are lipids with bound carbohydratesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  6. 6. Fluid Mosaic Model of Plasma MembraneCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  7. 7. Functions of Membrane Integral Proteins • Transport – channels or transportersCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  8. 8. Functions of Membrane Peripheral Proteins • Attach to inner cytoplasm • Part of glycocalyx outer coating as: • Receptors • Enzymes • Cell identification markers • Intercellular linkers Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  9. 9. Cell Environment Interactions• Membrane receptors used for: • Contact signaling – cell recognition • Electrical signaling – voltage-regulated “ion gates” in nerve and muscle tissue • Chemical signaling – neurotransmitters and hormones• Cell linkers anchor cells, assist in movement of cells past one another, send signals for repair and immunityCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  10. 10. Membrane Potential• Voltage across a membrane• Resting membrane potential • Ranges from Figure 3.13 –20 to –200 mV • Results from Na+ and K+ concentration gradients across the membrane • Differential permeability of the plasma membrane to Na+ and K+Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  11. 11. Membrane Transport• The cell membrane is selectively permeable to substances in the interstitial (extracellular) fluid• Passive transport processes require no energy• Active transport processes require energy Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  12. 12. DiffusionCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  13. 13. Passive Membrane Transport: Diffusion• Simple diffusion – movement from higher to lower concentration• Nonpolar, lipid-soluble substances diffuse directly through the cell lipid bilayer• Most small polar substances must go through integral protein channelsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  14. 14. Passive Membrane Transport: FacilitatedDiffusion• Large polar molecules (sugars) combine with integral protein transporters that aid transport across membrane Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  15. 15. Passive Membrane Transport: Osmosis• Diffusion of water across a semipermeable membrane• Occurs when the concentration of water is different on opposite sides of a selective, water permeable membraneCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  16. 16. Effect of Membrane Permeability on OsmosisCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  17. 17. Tonicity• Isotonic – solution has the same solute concentration as that of the cell• Hypotonic – solution has lesser solute concentration than that of the cell• Hypertonic – solution has greater solute concentration than that of the cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  18. 18. Passive Membrane Transport: Filtration• The passage of water and solutes through a membrane by pressure• Pressure gradient pushes substances from a higher- pressure area to a lower-pressure areaCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  19. 19. Active Transport (Solute Pump)• Solutes move against a concentration gradient (uphill)• Uses ATP to help move solutes across the membrane• Requires integral transport proteinsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  20. 20. Types of Active Transport • Symport system – two substances are moved across the membrane in the same direction • Antiport system – two substances are moved across the membrane in opposite directionsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  21. 21. Types of Active Transport• Primary active transport – phosphate from ATP causes conformational change of transport protein, which then transports substanceCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  22. 22. Types of Active Transport• Secondary active transport – as Na+ goes across membrane, other solutes (like glucose) “piggyback” across with itCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  23. 23. Vesicular Transport• Transport of large particles (macromolecules) across plasma membranes • Exocytosis – moves substance from the cell interior to the extracellular space • Endocytosis – enables macromolecules to enter the cell • Phagocytosis – engulf solids and bring them into the cell’s interior • Pinocytosis – engulf liquidsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  24. 24. Vesicular TransportCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  25. 25. Cytoplasm• Cytoplasm – material between plasma membrane and the nucleus; contains: • Cytosol – Colloid of water with dissolved protein, salts, sugars and other solutes • Inclusions – large chemical substances • Cytoplasmic organelles – metabolic machinery of the cellCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  26. 26. Cytoplasmic Organelles • Specialized cellular compartments with specialized functions – division of labor • Most are membrane - boundCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  27. 27. Cytoskeleton• The “skeleton”of the cell• Consists ofmicrofilaments,intermediatefilaments andmicrotubules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  28. 28. Microfilaments• Smallest strands like a beaded necklace• Function to change cell shape, cell movement, endocytosis, exocytosis and support microvilliCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  29. 29. Intermediate Filaments• Tough, insoluble protein fibers constructed like rope• Resist pulling forces in the cellCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  30. 30. Microtubules• Hollow tubes made of a spherical protein• Determine the overall shape of the cell and distribution of organellesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  31. 31. Centrioles• Small barrel-shaped organelles located near the nucleus• Pinwheel array of microtubules• Organize mitotic spindle during mitosis• Form the bases of cilia and flagellaCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  32. 32. Cilia• Hairlike, motile cellular extensions on exposed surfaces of certain cells• Move substances across cell surface Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  33. 33. Flagella• “Tail” of sperm cells for cell movementCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  34. 34. Ribosomes• Granules containing rRNA and protein• Site of protein synthesis• Free ribosomes synthesize soluble proteins• Membrane-bound ribosomes synthesize proteins to be incorporated into membranesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  35. 35. Endoplasmic Reticulum (ER)• Interconnected tubes and parallel membranes enclosing cisterna• Two varieties – rough ER and smooth ER Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  36. 36. Rough Endoplasmic Reticulum• External surface studded with ribosomes• Manufactures and transports protein containing compounds for internal use, integral proteins of plasma membranes and ultimately secretionCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  37. 37. Smooth Endoplasmic Reticulum• Function to synthesis and internal transport of lipid containing compoundsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  38. 38. Golgi Complex• Stacked and flattened membranous sacs• Functions in packaging compounds from the ER to make:• Secretory vesicles for export from the cell, plasma membrane components or lysosomesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  39. 39. Role of the Golgi ComplexCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  40. 40. Lysosomes• Spherical sacs containing digestive enzymes:• Digest ingested bacteria, viruses or toxins• Breakdown useless tissue• Degrade nonfunctional organelles• Cell suicideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  41. 41. Peroxisomes• Sacs that contain detoxifying enzymes to detoxify harmful substances, including free radicals – highly reactive chemicals that can damage cells• Ex: liver & kidneyCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  42. 42. Proteasomes• Contain proteases, enzymes that cut or degrade faulty cellular proteins into small peptides• 4 stacked rings around a central core• Too small to see under a light microscope• In both the cytosol & nucleus• Malfunction can result in Alzheimer’s & Parkinson’s diseasesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  43. 43. Mitochondria• Double membrane structure with inner membrane shelves called cristae and matrix between• Function to provide the cell’s ATP via aerobic cellular respiration• Contain their own DNA and RNACopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  44. 44. Nucleus• Gene-containing control center of the cell contains the genetic library with blueprints for nearly all cellular proteins; dictates the kinds and amounts of proteins to be synthesized• Contains nuclear envelope, nucleolus and chromatinCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  45. 45. NucleusCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  46. 46. Nuclear Envelope• Selectively permeable double membrane barrier containing pores• Pore complex regulates transport of large molecules into and out of the nucleusCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  47. 47. Nucleolus• Dark-staining spherical body within the nucleus• Site of ribosome productionCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  48. 48. Chromatin• Threadlike strands of DNA• Condense and form barlike bodies called chromosomes when the nucleus starts to divide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  49. 49. Protein Synthesis• DNA serves as master blueprint for protein synthesis• Genes are segments of DNA carrying instructions for a polypeptide chain• Triplets of nucleotide bases form the genetic library; each triplet specifies coding for an amino acidCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  50. 50. Transcription• Occurs in the nucleus• Transfer of information from the DNA strand to the mRNA as mRNA is synthesized• Each DNA triplet codes for a corresponding 3-base sequence of RNA, called a codon• Each codon corresponds to a DNA tripletCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  51. 51. TranscriptionCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  52. 52. Genetic CodeCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  53. 53. Translation• Involves all three types of RNA – mRNA, rRNA, and tRNA• Occurs in the cytoplasm at the ribosomes; mRNA leaves the nucleus and goes to the ribosomes• rRNA (part of ribosomes) is the anchoring site where mRNA is read and tRNA brings in the various amino acid to build a polypeptideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  54. 54. TranslationCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  55. 55. Roles of the Three Types of RNA• Messenger RNA (mRNA) carries the genetic information from DNA in the nucleus to the ribosomes in the cytoplasm• Ribosomal RNA (rRNA) is a structural component of ribosomes and site of protein synthesis• Transfer RNAs (tRNAs) bound to amino acids base pair their anticodons with the codons of mRNA at the ribosome to begin the process of protein synthesisCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  56. 56. Information Transfer from DNA to RNAto Make Proteins• DNA triplets are transcribed into mRNA codons• Codons base pair with tRNA anticodons at the ribosomes• Amino acids are peptide bonded at the ribosomes to form polypeptide chainsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  57. 57. Information Transfer from DNA to RNAto Make ProteinsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  58. 58. Cell Life Cycle• Interphase • Growth (G1), synthesis (S), growth (G2)• Cell division is essential for body growth and tissue repair • Mitosis (nuclear division) • Cytokinesis (cytoplasm division) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  59. 59. Interphase Parts• G1 – normal metabolic activity and growth• If cell gets signal to divide, then• S (synthesis) – DNA (chromosomes) and centrioles replicate• G2 – enzyme preparation for division Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  60. 60. DNA Replication• The DNA double helix unwinds into two complementary nucleotide chains; hydrogen bonds between nucleotides break• Freed nucleotide strands serve as templates for replication• Complementary nucleotide strands form: A-T; G-CCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  61. 61. Mitosis Phases• Prophase• Metaphase• Anaphase• TelophaseCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  62. 62. Prophase• Chromatin condenses into chromosomes• Nuclear envelope and nucleolus disappear• Centriole pairs separate and the mitotic spindle formsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  63. 63. Metaphase• Chromosomes cluster at the middle of the cell with their centromeres aligned at the exact center, or equator, of the cellCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  64. 64. Anaphase• Sister chromatids split• Chromosomes are pulled toward polesCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  65. 65. Telophase and Cytokinesis • Chromosomes nearly reach poles • New sets of chromosomes unwind into chromatin • New nuclear membrane and nucleolus reappear • Cytokinesis occurs at the same timeCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  66. 66. Cytokinesis• Cleavage furrow formed in late anaphase by a contractile ring• Cytoplasm is pinched in two as mitosis endsCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
  67. 67. Aging Theories• Mitosis ceases• Telemeres (tips of chromosomes) lost each mitosis• Glucose bridges to proteins• Free radical damage• AutoimmunityCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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