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Transcript
CHAPTER 4 CHARACTERISTICS OF PROKARYOTIC AND EUKARYOTIC CELLS Chapter Overview This chapter provides an in-depth look at the structure and function of prokaryotic and eukaryotic cells. A detailed study of prokaryotic structure is extremely valuable because it provides important information on how antibiotics work, how microbes undergo metabolism, how antibiotic resistant develops, and how differential stains such as the Gram stain work. Even though prokaryotes are considerably simpler than eukaryotic cells, they still possess many complex structures, such as peptidoglycan layers and endospores that are not found in any other living organism. However, when prokaryotic and eukaryotic cells are compared, similarities can also be found. For example, the cell membrane in prokaryotes is basically identical to the cell membrane in eukaryotic cells. A study of similarities and differences can help the student understand important biochemical and evolutionary changes. The last part of the chapter provides a brief presentation of the important mechanisms that move substances across cell membranes. An understanding of these mechanisms is essential to an understanding of how the cell functions. Both passive and active processes are presented, with the emphasis placed on those mechanisms that are most important to microbiologists. Since this chapter may be considered the foundation for later chapters, sufficient time in lecture should be devoted to ensure thorough coverage. Chapter Objectives Contrast the characteristics of eukaryotic and prokaryotic cell types. Describe the sizes, shapes, and arrangements of prokaryotic cells, especially as they relate to bacterial cells. Describe the basic structure and function of the cell membrane and cell wall of bacterial cells. List and describe the structure and function of internal cell components of bacteria, including endospores. Describe the structure and function of the external cell components of bacteria. Describe the general structure of eukaryotic cells. List and describe the structure and function of the internal components of eukaryotic cells. Describe the structure and function of the external components of eukaryotic cells. Explain the endosymbiotic theory and give examples of organelles that may have evolved by endosymbiosis. Describe the following passive processes, and explain their importance in cell function: simple diffusion, facilitated diffusion, and osmosis Describe the process of active transport, explaining how it differs from passive processes and why it is important in cell function. Describe the processes of exocytosis and endocytosis, and explain their importance in eukaryotic cell function. 4-1 Web Destinations http://www.bact.wisc.edu/Microtextbook/TOC.html On-line microbiology textbook http://www.cellsalive.com/cells/3dcell.htm Plant, animal, and bacterial cell models found at the Cells Alive website Michael Gregory’s site on cells http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20101/bio_1_menu.htm Michael Gregory’s General Biology 1 website, click on Mitosis Animation http://personal.tmlp.com/Jimr57/textbook/chapter3/chapter3.htm Virtual Cell Webpage A. Wiley’s cell structure animations for plants, animals, and bacteria http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structur e/cell_structure.htm Discussion Topics How could the process of endocytosis be used selectively to cause microbes to ingest antibiotics or other poisonous substances? Discuss the major unique bacterial components, peptidoglycan and 70S ribosomes. Explain how antibiotics target these unique characteristics to control bacterial infections. Chapter Outline I. Basic Cell Types A. Prokaryotic cells B. Eukaryotic cells (have membrane-bound organelles) II. Prokaryotic Cells A. Size, shape, and arrangement 1. Size 2. Shapes 3. Arrangements B. Overview of structure C. Cell wall 1. Basic functions 2. Components of cell walls a. Peptidoglycan b. Teichoic acids c. Outer membrane d. Lipopolysaccharide (endotoxin) e. Periplasmic space 3. Distinguishing bacteria by cell walls 4-2 D. E. F. III. a. Gram-positive bacteria b. Gram-negative bacteria c. Acid-fast bacteria d. Controlling bacteria by damaging cell walls 4. Wall-deficient organisms (L-forms) Cell membrane 1. Basic functions 2. Fluid-mosaic model a. Hydrophilic b. Hydrophobic Internal structure 1. Cytoplasm 2. Ribosomes 3. Nuclear region 4. Internal membrane systems 5. Inclusions a. Granules b. Vesicles 6. Endospores a. Sporulation b. Germination External structure 1. Flagella a. Types of flagella b. Composition c. Chemotaxis d. Phototaxis 2. Axial filaments (endoflagella) 3. Pili a. Conjugation pili b. Attachment pili 4. Glycocalyx a. Capsule b. Slime layer Eukaryotic Cells A. Overview of structure B. Plasma membrane C. Internal structure 1. Cytoplasm 2. Cell nucleus a. Basic features b. Chromosomes c. Mitosis d. Meiosis 3. Mitochondria 4-3 D. E. IV. 4. Chloroplasts 5. Ribosomes 6. Endoplasmic reticulum 7. Golgi apparatus 8. Lysosomes 9. Peroxisomes 10. Vacuoles 11. Cytoskeleton External structure 1. Flagella 2. Cilia 3. Pseudopodia 4. Cell walls Evolution by endosymbiosis 1. Endosymbiotic theory 2. Supporting evidence Movement of Substances across Membranes A. Basic characteristics B. Simple diffusion C. Facilitated diffusion D. Osmosis 1. Osmotic pressure 2. Tonicity E. Active transport F. Endocytosis and exocytosis 1. Endocytosis 2. Exocytosis 4-4