Cell Structure And Taxonomy PDF

CELL STRUCTURE AND TAXONOMY James Chua, MB(ASCPi) Introduction  Cell Fundamental unit of an organism Exhibits the basic characteristics of life: – Metabolism – all chemical reactions occurring in a cell – Growth and reproduction – Response to stimuli (light,...

CELL STRUCTURE AND TAXONOMY James Chua, MB(ASCPi) Introduction  Cell Fundamental unit of an organism Exhibits the basic characteristics of life: – Metabolism – all chemical reactions occurring in a cell – Growth and reproduction – Response to stimuli (light, heat, cold and chemicals) – Mutations  Early Work on Cells Robert Hooke – Inventor of the COMPOUND microscope – Coined the term “cell”  Early Work on Cells Matthias Schleiden – German botanist – Plant cell theory  Early Work on Cells Theodor Schwann – German zoologist – Animal cell theory  Early Work on Cells Rudolf Virchow – Biogenesis  Eukaryotes vs. Prokaryotes Eukaryotes Prokaryotes Nuclear membrane or Nucleoid “true” nucleus Lack complex system More complex of membranes and structure and organelles membrane-bound 10X smaller than organelles eukaryotes E.g., algae, protozoa, E.g., bacteria and fungi, plants, animals archaea and humans Eukaryotic Cell Structure  Cell Membrane AKA plasma, cytoplasmic or cellular membrane Selective permeability – Regulates passage of nutrients, waste and secretions into and out of the cell. Mosaic of proteins and phospholipids  Nucleus Controls all cell functions Parts: – Chromosomes DNA and histones – Nucleoplasm Gelatinous matrix – Nuclear membrane Nuclear pores – Nucleolus rRNA production  Cytoplasm Semi-fluid, gelatinous, nutrient matrix which contains the organelles Site for most metabolic reactions Cytosol – Cytoplasm without the organelles or storage granules  Endoplasmic reticulum Highly convoluted interconnected system of membranes Rough and smooth portions Ribosomes – Protein synthesis – 40, 60 and 80S – Svedberg units - sedimentation coefficients Ribosome  Golgi Complex AKA Golgi appratus or body “Packaging plants” – Converts linear proteins to functional form – Packages proteins into membrane- enclosed vesicles for storage or export  Lysosomes Lysozyme – Breaks down foreign material – Autolysis  Peroxisomes Hydrogen peroxide production and degradation Catalase – 2H2O2  2H2O+ O2 Prominent in mammalian liver cells.  Mitochondria Adenosine triphosphate (ATP) – ATP  ADP + PO4 + Energy Believed to have evolved from bacteria living within eukaryotes  Plastids Energy-producing organelle in plants and algae E.g., chloroplasts Photosynthesis – CO2 + H2O → CHO and O2  Cytoskeleton System of fibers Types throughout the – Microtubules cytoplasm Spherical tubulin protein subunits Structure, cell – Intermediate division, filaments contraction, – Microfilaments motility and chromosome movement  Cell Wall Not present in all eukaryotes Rigidity, shape and protection Less complex than prokaryotic cell wall Composition: – Cellulose (in algae and plants), pectin, lignin, chitin (in fungi and crustaceans) and some mineral salts  Flagella and Cilia Organelles of locomotion Microtubules in a 9 + 2 arrangement  Flagella and Cilia Flagella cilia Long and thin Short and thinner than Whip-like movement flagella Membrane-bound Coordinated and E.g., spermatozoa and rhythmic movement certain protozoa and More numerous than algae flagella E.g., certain protozoa and epithelial cells lining the respiratory tract Giardia lamblia Balantidium coli Prokaryotic Cell Structure  Prokaryotic Cell Envelope Cell Membrane Cell wall Glycocalyx  Cell Wall Gram positive Gram negative Thick peptidoglycan Thinner peptidoglycan Teichoic and Lipid outer membrane lipoteichoic acid molecules Cell Wall  Cell Wall Mycoplasma spp. – Cell wall-less Archaeans – Peptidoglycan-less cell walls  Glycocalyx Capsule Slime layer Highly organized Loosely attached to Firmly attached to cell wall cell wall Anti-phagocytic Sliding and gliding Examples: – Haemophilus influenzae Example – Klebsiella pneumoniae – Pseudomonas – Neisseria meningitidis aeruginosa – Streptococcus pneumoniae Colonial morphology – Encapsulated: smooth, mucoid and glistening – Non-encapsulated: dry and rough Capsule  Prokaryotic Chromosome Single, long, supercoiled, circular DNA molecule Nucleoid – DNA-occupied space in cytoplasm Plasmid – Extrachromosomal, circular, double- stranded DNA – Also found in yeast cells  Cytoplasm Water Enzymes Dissolved oxygen Waste products Essential nutrients Biomolecules  Cytoplasmic Particles Ribosomes Granules – 30, 50 and 70S – Starch, lipids, sulfur, iron or other stored substances  Flagella 3 to 4 flagellin threads twisted like a rope Arrangement: – Peritrichous – Lophotrichous – Amphitrichous – Monotrichous  Axial filaments Spirochetes (spiral- shaped bacteria) Two flagella like fibrils (one attached at each end) which extend toward each other and wrap round the organism Spiral, helical and inchworm movements Spirochetes  Pili (Fimbriae) Hair like structures observed in G(-) bacteria NOT associated with motility Functions: Attachment and transfer of genetic material (i.e., conjugation)  Spores (Endospores) Discovered by John Tyndall Sporulation – Low moisture and nutrient supply Resistance to heat, cold, drying and most chemicals Location: terminal or subterminal Examples: – Bacillus spp. – Clostridium spp. Bacillus anthracis Reproduction  Eukaryotic Cell Reproduction Mitosis Meiosis 2N (diploid) 1N (haploid) Somatic cells Gametes One division Two divisions 2 genetically identical 4 genetically different daughter cells daughter cells Mitosis Meiosis  Prokaryotic Cell Reproduction Binary fission – Generation time – pH, temperature, availability of nutrients – 10 minutes to 24 hours or longer Taxonomy  Taxonomy Classification, nomenclature and identification of organisms Separation into taxa (i.e., groups) based on similarities Binomial nomenclature system Classification Schemes – Five-Kingdom – Three-Domain  Taxa Kingdom, division/phylum, class, order, family, genus and species King David/Philip Came Over For Good Spaghetti  Binomial Nomenclature System Carolus Linnaeus Species – Genus (pl., genera) + specific epithet – Escherichia coli – sp. and spp. Five-Kingdom Classification Robert H. Whittaker Classification – Procaryotae (Monera) – Protista Algae and protozoa – Fungi – Plantae – Animalia Three-Domain Classification Carl R. Woese Differences in rDNA sequences Classification – Archaea – Bacteria – Eukarya FIN