Cell Structure and Function Chapter 3 Cell Structure and Function 6/27/11 MDufilho

What is the difference between a living thing and a non living thing? Processes of Life What is the difference between a living thing and a non living thing? 6/27/11 MDufilho 2

Figure 3.1 Examples of types of cells-overview 6/27/11 MDufilho 3

How are these cells similar? Prokaryote Eukaryote 6/27/11 MDufilho

External Structures of Bacterial Cells Two Types of Glycocalyces Capsule Composed of organized repeating units of organic chemicals Firmly attached to cell surface May prevent bacteria from being recognized by host Slime layer Loosely attached to cell surface Water soluble Sticky layer allows prokaryotes to attach to surfaces 6/27/11 MDufilho © 2012 Pearson Education Inc. 5

Figure 3.5 Glycocalyces-overview Glycocalyx (capsule) Glycocalyx (slime layer) 6/27/11 MDufilho 6

External Structures of Bacterial Cells Flagella Are responsible for movement Have long structures that extend beyond cell surface Are not present on all bacteria 6/27/11 MDufilho © 2012 Pearson Education Inc. 7

Figure 3.6 Proximal structure of bacterial flagella-overview Filament H o k Direction of rotation during run Rod Peptidoglycan layer (cell wall) Protein rings Cytoplasmic membrane Cytoplasm Filament H o k Outer protein rings Outer membrane Rod Cell wall Gram  Gram  Peptidoglycan layer Basal body Integral protein Inner protein rings Cytoplasmic membrane Cytoplasm Integral protein 6/27/11 MDufilho 8

External Structures of Bacterial Cells ANIMATION Flagella: Movement 6/27/11 MDufilho © 2012 Pearson Education Inc. 9

Figure 3.7 Micrographs of basic arrangements of bacterial flagella-overview 6/27/11 MDufilho 10

Figure 3.8 Axial filament-overview Endoflagella rotate Axial filament rotates around cell Axial filament Outer membrane Cytoplasmic membrane Spirochete corkscrews and moves forward Axial filament 6/27/11 MDufilho 11

Figure 3.10 Fimbriae Flagellum Fimbria 6/27/11 MDufilho 12

Figure 3.11 Pili Conjugation pilus 6/27/11 MDufilho 13

Bacterial Cell Walls Bacterial Cell Walls Provide structure and shape and protect cell from osmotic forces Assist some cells in attaching to other cells or in resisting antimicrobial drugs Can target cell wall of bacteria with antibiotics Give bacterial cells characteristic shapes Composed of peptidoglycan Scientists describe two basic types of bacterial cell walls, Gram-positive and Gram-negative 6/27/11 MDufilho © 2012 Pearson Education Inc. 14

N-acetylglucosamine NAG N-acetylmuramic acid NAM Figure 3.13 Comparison of the structures of glucose, NAG, and NAM-overview Glucose N-acetylglucosamine NAG N-acetylmuramic acid NAM 6/27/11 MDufilho 15

Gram-Positive Bacterial Cell Walls Relatively thick layer of peptidoglycan Contain unique polyalcohols called teichoic acids and lipotechoic acid – have a negative charge Appear purple following Gram staining procedure Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation 6/27/11 MDufilho © 2012 Pearson Education Inc. 16

Figure 3.15a Comparison of cell walls of Gram-positive and Gram-negative bacteria Peptidoglycan layer (cell wall) Cytoplasmic membrane Gram-positive cell wall Lipoteichoic acid Teichoic acid Integral protein 6/27/11 MDufilho 17

Gram-Negative Bacterial Cell Walls Have only a thin layer of peptidoglycan Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) May be impediment to the treatment of disease Appear pink following Gram staining procedure 6/27/11 MDufilho © 2012 Pearson Education Inc. 18

Figure 3.15b Comparison of cell walls of Gram-positive and Gram-negative bacteria Porin Outer membrane of cell wall Porin (sectioned) Peptidoglycan layer of cell wall Periplasmic space Cytoplasmic membrane Gram-negative cell wall Phospholipid layers n Lipopolysaccharide (LPS) O side chain (varies In length and composition) Integral proteins Core polysaccharide Lipid A (embedded in outer membrane) Fatty acid 6/27/11 MDufilho 19

Bacterial Cytoplasmic Membranes Structure Referred to as phospholipid bilayer Composed of lipids and associated proteins Fluid mosaic model describes current understanding of membrane structure 6/27/11 MDufilho © 2012 Pearson Education Inc. 20

Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer Head, which contains phosphate (hydrophilic) Phospholipid Tail (hydrophobic) Integral proteins Cytoplasm Integral protein Phospholipid bilayer Peripheral protein Integral protein 6/27/11 MDufilho 21

Bacterial Cytoplasmic Membranes Remember the Functions??? What are they??? 6/27/11 MDufilho © 2012 Pearson Education Inc. 22

Cytosol – Liquid portion of cytoplasm Cytoplasm of Bacteria Cytosol – Liquid portion of cytoplasm Inclusions – May include reserve deposits of chemicals Endospores – Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions 6/27/11 MDufilho © 2012 Pearson Education Inc. 23

Figure 3.23 Granules of PHB in the bacterium Azotobacter chroococcum Polyhydroxybutyrate 6/27/11 MDufilho 24

Figure 3.24 The formation of an endospore-overview Cytoplasmic membrane Cell wall DNA is replicated. A cortex of calcium and dipicolinic acid is deposited between the membranes. Cortex DNA Vegetative cell Spore coat forms around endospore. Spore coat DNA aligns along the cell’s long axis. Outer spore coat Endospore matures: completion of spore coat and increase in resistance to heat and chemicals by unknown process. Cytoplasmic membrane invaginates to form forespore. Forespore Endospore Outer spore coat Endospore is released from original cell. Cytoplasmic membrane grows and engulfs forespore within a second membrane. Vegetative cell’s DNA disintegrates. First membrane Second membrane 6/27/11 MDufilho 25

Nonmembranous Organelles Cytoplasm of Bacteria Nonmembranous Organelles Ribosomes Sites of protein synthesis Cytoskeleton Plays a role in forming the cell’s basic shape 6/27/11 MDufilho © 2012 Pearson Education Inc. 26

Endosymbiotic Theory Mitochondria and chloroplasts have 70S ribosomes, circular DNA, and two membranes. Why???? 6/27/11 MDufilho © 2012 Pearson Education Inc. 27