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Introduction to Prokaryotes and Eukaryotes

Introduction to Prokaryotes and Eukaryotes. Chapter 6, 27. Three Domains of Life. Archaea Bacteria Eukarya. Three Domains of Life. There are 2 main categories of cells: Prokaryotes – Bacteria Eukaryotes – Plants, Fungi, Protists , Animals . Early life: First cells . 3.5-2.0 BYA

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Introduction to Prokaryotes and Eukaryotes

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  1. Introduction to Prokaryotes and Eukaryotes Chapter 6, 27

  2. Three Domains of Life • Archaea • Bacteria • Eukarya

  3. Three Domains of Life • There are 2 main categories of cells: • Prokaryotes – Bacteria • Eukaryotes – Plants, Fungi, Protists, Animals

  4. Early life: First cells • 3.5-2.0 BYA • First cells were simple • Branched into two major lines: bacteria and archaea Samples of Archeans from an ocean vent

  5. Bacterial Phylogeny Ancient bacteria • Note the presence of a common ancestor • Split off into two domains: archaea and bacteria

  6. Archaea • Diverse group of primitive bacteria • AKA “extremophiles” • Methanogens • Halophiles • Thermophiles

  7. Eubacteria, or Bacteria • Very diverse group of bacteria • More helpful than harmful • Categorized by: • Shape • Arrangement • Cell wall composition • Metabolic requirements

  8. Bacterial Structure

  9. Bacterial Shapes • Cocci: round • Bacilli: rod-shaped • Spirochete: spiral-shaped

  10. Cell Wall • Eubacteria possess a cell wall in addition to their membrane • This cell wall is composed of sugars and proteins: peptidoglycans • Hans Gram (1884) developed differential stain to distinguish one type from another: Gram stain

  11. Metabolic requirements • Obligate aerobes – require oxygen for cellular respiration • Obligate anaerobes – cannot live in the presence of oxygen • Facultative anaerobes – can live with or without oxygen

  12. Metabolism of Microbes: Autotrophs Photoautotroph: uses light energy to generate organic compounds from CO2 cyanobacteria Chemoautotroph: uses energy from inorganic chemicals and CO2 to produce organic compounds Sulfolobus

  13. Photoheterotroph: uses light energy but obtains organic compounds from other organisms Rhodobacter Chemoheterotroph: organism that uses organic chemicals obtained from other organisms for energy Example: E. coli Metabolism of Microbes: Heterotrophs

  14. Role of Bacteria in the Environment • Photoautotrophs generate O2 in the atmosphere • Symbiotic relationships • Bacteria also fix nitrogen so that plants can use it: nitrogen fixation • Conversion of nitrogen gas to ammonia • Bacteria are decomposers of dead material

  15. Role of Bacteria to Humans • Used in research and biotechnology applications • Many bacteria are used in food production: • Sauerkraut • Cheese • Yogurt • Many bacteria are agents of disease • Necrotizing fasciitis (“flesh eating” disease)

  16. Cellular Theory All living things are composed of cell All cells come from pre-existing cells Cells are the basic unit of structure and function in living things

  17. Organelles • A specialized structure that performs a certain function within a cell • Number and complexity depends on cell type

  18. All Cells Have… • Plasma membrane • Boundary of cell • Controls what enters, leaves • Role in communication

  19. All Cells Have… • Cytoplasm/Cytosol • Semi-fluid substance • Where organelles are found

  20. All Cells Have… • Chromosomes • Genetic material (DNA)

  21. All Cells Have… • Ribosomes • Site where protein is made

  22. Prokaryotes: Small in size (range: 2-20m) Genome is singular chromosome not organized around proteins Do not have membrane-bound organelles Flagella do not have 9+2 arrangement Ribosomes 70s Eukaryotes: Large size (to 100m) Genome organized around proteins; multiple chromosomes present Flagella found in 9+2 arrangement Contain membrane-bound organelles Ribosomes 80s Prokaryotes vs. Eukaryotes

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