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Transcript
Cells Scientists • Hooke-saw cork cells under a microscope • Van Leeuweenhoek – saw living bacteria • Pasteur – studied bacteria and developed the germ theory that said that ‘germs’ cause disease. He also developed the first vaccines. • Koch – rules to test if a germ is the cause of a specific disease • Margulis – tested DNA in mitochondria and found it was the same as bacteria DNA Cell Theory • All living organisms are composed of one or more living cells • Cells are the basic units of life • All cells come from preexisting cells Microscopes • Compound Light Microscope – series of glass lens that can be no better than 1000X, but can be used to view living cells • Electron microscopes – aims a beam of electrons at thin slices of cells (dead) – Transmission electron microscope (TEM) – Scanning electron microscope (SEM) Microscopes Cell size • As cell size increases, the surface area to volume ratio decreases • Rates of chemical exchange may then be inadequate for cell size • Cell size, therefore, remains small Cell Size Cell Size Basic Cell Types • Prokaryotes – cells without a nucleus or other membrane bound organelles – Example: most unicellular organisms, e.g., bacteria • Eukaryotes – cells with a nucleus and other membrane bound organelles (ER, mitochondria, Golgi apparatus, chloroplast, lysosome) Plasma Membrane The Lipid Bilayer • Lipids of the bilayer – fluid or liquid-crystalline state • Proteins move within the membrane Hydrophilic region of protein Hydrophobic region of protein Phospholipid bilayer Peripheral protein Integral (transmembrane) protein (b) Fluid mosaic model. According to this model, a cell membrane is a fluid lipid bilayer with a constantly changing “mosaic pattern“ of associated proteins. Fig. 5-2b, p. 108 Cytoplasm • Environment inside cell membrane • Cytoskeleton – supporting network of long, protein fibers that form a network and anchor for the cell organelles Membrane structure • Phospholipids~ membrane fluidity • Cholesterol~ membrane stabilization • “Mosaic” Structure~ proteins • Membrane carbohydrates ~ cell to cell recognition; Nucleus • Genetic material... •chromatin •chromosomes • Nucleolus:; ribosome synthesis • Double membrane envelope with pores • Protein synthesis Ribosomes • Protein manufacture Endomembrane system, I • Endoplasmic reticulum (ER) • Smooth ER •no ribosomes; •synthesis of lipids • Rough ER •with ribosomes; •synthesis of proteins Endomembrane system, II • Golgi apparatus – •ER products are modified, stored, and then shipped Endomembrane system, III • Lysosomes •sac of hydrolytic enzymes; digestion of macromolecules • Tay-Sachs disease~ lipid-digestion disorder Other membranous organelles, I • Mitochondria • quantity in cell correlated with metabolic activity; •cellular respiration •contain own DNA Other membranous organelles, II • Chloroplast (doubled membranous plastid) •photosynthesis •own DNA Peroxisomes • Metabolism of fatty acids; detoxification of alcohol (liver) Cellular Transport • Passive Transport – does not require energy – Diffusion – Across a membrane • Osmosis • Facilitated diffusion • Active Transport – requires energy – Sodium/Potassium pump – Transport of Large Particles • Endocytosis • Exocytosis Diffusion Osmosis Water balance • Osmoregulation~ control of water balance • Hypertonic~ higher concentration of solutes • Hypotonic~ lower concentration of solutes • Isotonic~ equal concentrations of solutes • • • • Cells with Walls: Turgid (very firm) Flaccid (limp) Plasmolysis~ plasma membrane pulls away from cell wall Turgor and Plasmolysis Facilitated Diffusion Types of Active Transport • Sodium-potassium pump • Exocytosis~ secretion of macromolecules by the fusion of vesicles with the plasma membrane • Endocytosis~ import of macromolecules by forming new vesicles with the plasma membrane •phagocytosis •pinocytosis 2. Phosphate group is transferred from ATP to transport protein. 3. Phosphorylation causes carrier protein to change shape, releasing 3 Na+ outside cell. 1. Three Na+ bind to transport protein. 4. Two K+ bind to transport protein. 6. Phosphate release causes 5. Phosphate is released. carrier protein to return to its original shape. Two K+ ions are released inside cell. Fig. 5-17b, p. 121 Phagocytosis Large particles enter cell