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The Central Dogma of Biology among other things…

The Central Dogma of Biology among other things…. What is the Central Dogma?. The process by which we convert the message stored in DNA into a functional protein DNA  mRNA  tRNA  Protein!. Step 1: DNA  mRNA. Transcription (copy the DNA message into an mRNA strand) DNA must “unzip”

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The Central Dogma of Biology among other things…

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  1. The Central Dogma of Biologyamong other things…

  2. What is the Central Dogma? • The process by which we convert the message stored in DNA into a functional protein DNA  mRNA  tRNA  Protein!

  3. Step 1: DNA  mRNA • Transcription (copy the DNA message into an mRNA strand) • DNA must “unzip” • Helicase is the enzyme that “unzips” DNA • An RNA copy is made • Polymerase • DNA “triplets” (groups of 3 nitrogenous bases in DNA) become mRNA “codons” (complementary groups of 3 nitrogenous bases in mRNA) • Once the RNA copy is made, it travels out into the cytoplasm

  4. Step 2: mRNA  tRNA  Protein • Translation • The “language” of the nucleic acids is translated into the “language” of the amino acids (the tRNA acts as a literal “translator”) • “codons” become “anticodons” (3 nitrogenous bases in tRNA that are complementary to the mRNA codons). Each anticodon corresponds to one specific amino acid • When complete, AA chain is released!

  5. Protein Folding • Proteins must achieve a specific three-dimensional conformation before they become functional • Spontaneous folding (protein folds itself) • Chaperoned folding (protein is physically folded by something else)

  6. Organelles • Endoplasmic Reticulum • Smooth ER – lipid synthesis and site of chemical rxn’s • Rough ER – protein synthesis (“rough” because covered with ribosomes!) • Ribosomes – protein production factories in the cell • Nucleus – contains genetic material; command center of cell • Golgi Apparatus – responsible for packaging and shipping in the cell • Lysosomes – contain digestive enzymes to break down wastes • Mitochondria – breaks down glucose to provide cell with ATP • Peroxisomes – seek and destroy harmful substances in the cell • Centrioles – protein bundles that serve as anchors during cell division

  7. Cytoskeleton • Microtubules (hollow cylinders) • Determine shape and distribution of organelles • Microfilaments • Cell motility (movement) and changes in cell shape • Intermediate Filaments (see Desmosomes) • Help form Desmosomes

  8. Cell Cycle • Interphase – period of growth and metabolism in the cell • G1 – cytoplasm doubles in volume, proteins are synthesized, organelles are copied • Synthesis – growth stops, DNA replicates • G2 – centrioles replicate, growth continues • Mitosis – division of the nucleus; end result is two identical daughter cells • Prophase – preparation for division: nuclear envelope and nucleolus disappear, chromatin condenses into chromosomes, centrioles migrate to opposite ends of the cell, spindle fibers appear) • Metaphase – spindle fibers attach to chromosomes and align them at the middle of the cell • Anaphase – spindle fibers shorten, drawing sister chromatids to opposite ends of the cell • Telophase – spindle fibers disappear, nuclear envelope and nucleolus reappear, chromatids uncoil into chromatin, cytoplasm begins to pinch • Cytokinesis – division of the cytoplasm; cells re-enter interphase

  9. Plasma Membrane • Or Selectively Permeable Membrane or Phospholipid Bilayer or Cell Membrane or Membrane or Lipid Bilayer • Flexible boundary between the cell and its environment • Purpose: maintain homeostasis!

  10. Membrane Junctions • Junctions form between adjacent cells • Tight Junctions • Impermeable barriers • Their purpose is to bind cells together into “sheets” • Act like “zippers” for adjacent cells • Desmosomes • Anchoring Junctions • Prevent tearing of tissues due to mechanical stress • Gap Junctions • Allow communication between cells • Made of Connexons • Protein channels within gap junctions

  11. Membrane Transport • Passive Transport (requires no energy) • Diffusion: random movement of solute particles across a membrane from an area of high concentration to an area of low concentration • Osmosis: diffusion of water – here our focus is on the concentration of solvent particles (not solute!!). Osmosis typically occurs in the opposite direction of simple diffusion • Active Transport (requires energy; goes AGAINST a concentration gradient) • Solute Pumping (requires a carrier protein) • Sodium-potassium pump • Bulk Transport • Endocytosis (cell takes up materials by enveloping it with a membrane) • Exocytosis (cell expels materials) • Phagocytosis (“cellular eating” – defense mechanism in the cell) • Pinocytosis (“cellular drinking” – endocytosis for materials dissolved in solution)

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