Chapter 3 Cell Structure and Function - Brazosport …

1 Chapter 3 Cell Structure and Function MDufilho 8/20/2017 1 Processes of Life What is the difference between a living thing and a non-living thing? What are the processes of life? 8/20/2017 2 Figure Examples of types of cells . 8/20/2017 MDufilho 3 How are these cells similar? 8/20/2017 MDufilho 4 Prokaryote Eukaryote Prokaryotic and Eukaryotic cells : An Overview Tell Me Why In 1985, an Israeli scientist discovered a single-celled microbe, Epulopiscium fishelsoni. This organism is visible with the naked eye.

2 Why did the scientist think Epulopiscium was eukaryotic? What discovery revealed that the microbe is really a giant bacterium? 8/21/2014 MDufilho 5 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 8/20/2017 MDufilho 6 Figure Glycocalyces.

3 Glycocalyx (capsule) Glycocalyx (slime layer) 8/20/2017 MDufilho 7 External Structures of Bacterial cells Flagella Are responsible for movement Have long structures that extend beyond cell surface Are not present on all bacteria Structure Composed of filament, hook, and basal body Basal body anchors the filament and hook to cell wall 8/20/2017 MDufilho 8 Figure Proximal Structure of bacterial flagella. Filament Direction of rotation during run Peptidoglycan layer (cell wall) Cytoplasmic membrane Cytoplasm Protein rings Rod Filament Outer membrane Peptidoglycan layer Cytoplasmic membrane Cytoplasm Cell wall Outer protein rings Rod Integral protein Inner protein rings Integral protein Basal body Gram Gram + 8/20/2017 MDufilho 9 Figure Axial filament.

4 Axial filament rotates around cell Outer membrane Cytoplasmic membrane Axial filament Spirochete corkscrews and moves forward Endoflagella rotate Axial filament 8/20/2017 MDufilho 10 Figure Fimbriae. Flagellum Fimbria 8/20/2017 MDufilho 11 Figure Pili. Pilus 8/20/2017 MDufilho 12 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.

5 Gram-positive and Gram-negative 8/20/2017 MDufilho 13 Sugar chain Tetrapeptide (amino acid) crossbridge Connecting chain of amino acids Figure Possible Structure of peptidoglycan. 8/20/2017 MDufilho 14 Bacterial Cell Walls Gram-Positive Bacterial Cell Walls Relatively thick layer of peptidoglycan Contain unique chemicals called teichoic acids Appear purple following Gram staining procedure Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation 8/20/2017 MDufilho 15 Prokaryotic Cell Walls Gram-Negative Bacterial Cell Walls Have only a thin layer of peptidoglycan Bilayer membrane outside the peptidoglycan contains phospholipids, proteins.

6 And lipopolysaccharide (LPS) Lipid A portion of LPS can cause fever, vasodilation, inflammation, shock, and blood clotting May impede the treatment of disease Appear pink following Gram staining procedure 8/20/2017 MDufilho 16 Prokaryotic Cell Walls Bacteria Without Cell Walls A few bacteria lack cell walls Often mistaken for viruses due to small size and lack of cell wall Have other features of prokaryotic cells such as ribosomes 8/20/2017 MDufilho 17 Bacterial Cytoplasmic Membranes Structure Referred to as phospholipid bilayer Composed of lipids and associated proteins.

7 Integral proteins Peripheral proteins Fluid mosaic model describes current understanding of membrane Structure 8/20/2017 MDufilho 18 Bacterial Cytoplasmic Membranes functions ? 8/20/2017 MDufilho 19 Cytoplasm of Bacteria Cytosol Liquid portion of cytoplasm Mostly water Contains cell's DNA in region called the nucleoid Inclusions May include reserve deposits of chemicals 8/20/2017 MDufilho 20 Figure Granules of PHB in the bacterium Azotobacter chroococcum. Polyhydroxybutyrate 8/20/2017 MDufilho 21 Cytoplasm of Bacteria Endospores Unique structures produced by some bacteria Defensive strategy against unfavorable conditions Vegetative cells transform into endospores when multiple nutrients are limited Resistant to extreme conditions such as heat, radiation, chemicals 8/20/2017 MDufilho 22 Figure Formation of an endospore.

8 Steps in Endospore Formation DNA is replicated. Cytoplasmic membrane invaginates to form forespore. Cytoplasmic membrane grows and engulfs forespore within a second membrane. Vegetative cell's DNA disintegrates. A cortex of pepti- doglycan is deposited between the membranes; meanwhile, dipicolinic acid and calcium ions accumulate within the center of the endospore. Spore coat forms around endospore. Endospore matures: Completion of spore coat. Increase in resistance to heat and chemicals by unknown processes. Endospore is released from original cell.

9 Cell wall Cytoplasmic membrane DNA Vegetative cell Forespore First membrane Second membrane Cortex Spore coat Outer spore coat Endospore 8/20/2017 MDufilho 23 Cytoplasm of Prokaryotes Nonmembranous Organelles Ribosomes Sites of protein synthesis Composed of polypeptides and ribosomal RNA Cytoskeleton Composed of three or four types of protein fibers Can play different roles in the cell: Cell division Cell shape Segregate DNA molecules Move through the environment 8/20/2017 MDufilho 24 External Structure of Eukaryotic cells Glycocalyces Not as organized as prokaryotic capsules Help anchor animal cells to each other Strengthen cell surface Provide protection against dehydration Function in cell-to-cell recognition and communication 8/20/2017 MDufilho 25 Eukaryotic Cell Walls and Cytoplasmic Membranes Fungi, algae, plants.

10 And some protozoa have cell walls Composed of various polysaccharides: Cellulose found in plant cell walls Fungal cell walls composed of cellulose, chitin, and/or glucomannan Algal cell walls composed of a variety of polysaccharides 8/20/2017 MDufilho 26 Eukaryotic Cell Walls and Cytoplasmic Membranes All eukaryotic cells have cytoplasmic membrane Are a fluid mosaic of phospholipids and proteins Contain steroid lipids to help maintain fluidity Contain regions of lipids and proteins called membrane rafts Control movement into and out of cell 8/20/2017 MDufilho 27 Cytoplasm of Eukaryotes Flagella Structure and Arrangement Differ structurally and