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BIO206H5 (60)
Chapter 1

BIO206 Chapter 1.pdf

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University of Toronto Mississauga
George S Espie

Chapter 1 September-12-13 12:07 PM - DNA polymer chains – 4 nucleotides (monomers) - Transcribed DNA --> RNA - Messenger RNA --> messages are translated into protein - Proteins are built from amino acids (there are 20) - Amino acids have different conformation - Viruses have no ability to reproduce outside its host - Daughter cells = parent cells except when there is mutation - Evolution favors mutation that will change for the better (able to survive and reproduce) ○ Basis of evolution – the process by which species become gradually modified and adapted to their env Genes Provide the Instructions for Cellular Form, Function, and Complex Behaviour - Genome – library of genetic information in DNA Cells Under the Microscope - Light microscopes were used to look at cells - Electron microscopes (1930) – use to see details The Invention of the Light Microscopes Led to the Discovery of Cells - Robert Hooke(1665) examined the cork using a simple microscope and discovered cells - Antoni van Leeuwenhoek observed living cells - 19th century - microscopes began to be widely used - 2 publications by Matthias Schleiden (1838) and Theodor Schwann (1839) gave birth to cell biology - Cell theory - cell are formed by the division of existing cells - Louis Pasteur - cells do not arise spontaneously - Darwin's theory of evolution Cells, Organelles, and Even molecules can be seen under the microscope - Extracellular matrix - dense material often made by protein fibers embedded in a polysaccharide gel - Diameter of cell - 5-20um - Light microscope - magnify upto 1000 times, details as small as 0.2um ○ Things needed: light focused on the specimen, specimen is prepared to allow light to pass, and set of lenses(objective and eyepiece) - Fluorescence microscopes - filters light before reaches the specimen. Only wavelengths that excite the dye can pass. - Confocal microscope - specialized type of fluorescence microscope (scans specimen with a laser beam) ○ Allows optical section (sharp image of the plane of focus ) and 3D image - Transmission electron microscope (TEM) - used to look at thin sections - Scanning electron microscope (SEM) - used to look at surface details - Internal structure of cell (difficult to see because they're small and transparent) approach: stain cells, look at difference in refractive index - Before viewing in light microscope, samples should be: fixed, embedded in a solid wax/ resin, sectioned in thin slices, and stained - For electron microscope: same but sections have to be thinner and no viewing of live wet cells - Organelles are seen inside. Plasma membrane (external membrane) Internal membranes (surrounding the organelle) Procaryotic cell - Bacteria simplest structure - no organelles/ nucleus - "pro" = before "karyon" = nucleus, kernel - Most diverse of cells - Mitochondria - generate energy for the eucaryotic cell - Can live from any organic material/ some inorganic - Some perform photosynthesis - Chloroplasts evolved from photosynthetic bacteria Procaryotes: bacteria and archaea - Have DNA but no nucleus - Bacteria - live in soil, make us ill - Bacteria - live in soil, make us ill - Archaea live in extreme habitats (hostile to most other cells) Eucaryotic cell - Some are single-celled: amoebae, yeasts - Plants, animal, fungi - Nucleus: enclosed in nuclear envelope, information store of the cell, contains most of DNA - Chromosomes: become visible when a cell is about to divide - Mitochondria: generate usable energy from food to power the cell ○ Two membranes: outer and inner membrane ○ Contain their own DNA ○ Resemble bacteria (symbiotic relationship between host eucaryote and engulfed bacterium) So they are most likely evolved from engulfed bacteria ○ ○ Opening up and spinning cells in centrifuge gave more detail on mitochondria- they are generators of chemical energy. ○ Oxidize food molecules to produce ATP (adenosine triphosphate) ○ Consumes O2 and release CO2 - cellular respiration ○ Anaerobic - if oxygen isn't essential (many procaryotes and few eucaryotes) ex: Glardia - Chloroplast - enable plants to capture energy from sunlight ○ Found in plants and algae ○ Contain chlorophyll ○ Perform photosynthesis and manufacture energy-rich sugar molecules, release O2 as by- product ○ Contain own DNA, and thought to evolved from bacteria - Internal membranes - create intra
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