Cell Structure and Function

Transcription

1 PowerPoint Lecture Presentations prepared by Mindy Miller-Kittrell, North Carolina State University C H A P T E R 3 Cell Structure and Function

2 Handout Structure-Function Table Handout Prok vs Euk Table

3 Structure = specific Function Humming bird feeder

4 Capsule enhances the ability of bacteria to cause disease

5 Prokaryotic and Eukaryotic Cells: An Overview Eukaryotes (true nucleus) Have nucleus membrane bound Have internal membrane-bound organelles Are larger: µm in diameter Have more complex structure Composed of algae, protozoa, fungi, animals, and plants

6 Prokaryotic and Eukaryotic Cells: An Overview Prokaryotes (before nucleus) Lack nucleus Lack various internal structures bound with phospholipid membranes Are typically 1.0 µm in diameter or smaller Have a simple structure eg bacteria and archaea

7 Figure 3.2 Typical prokaryotic cell. Inclusions Ribosome Cytoplasm Nucleoid Glycocalyx Cell wall Flagellum Cytoplasmic membrane

8 External Structures of Bacterial Cells Glycocalyces Structure - Gelatinous, sticky substance surrounding the outside of the cell. Composed of polysaccharides, polypeptides, or both Function avoid dessication, adhesion, protect from host defense

9 External Structures of Bacterial Cells Two Types of Glycocalyces Capsule Firmly attached to cell surface Prevent bacteria from being recognized by host Slime layer Loosely attached to cell surface Water soluble Sticky layer allows prokaryotes to attach to surfaces - forms e.g. Dental plaques BIOFILMS check page 63 for highlight

10 External Structures of Bacterial Cells Flagella Structure Composed of 3 units - filament, hook, and basal body Basal body anchors the filament and hook to cell wall Filament made of flagellin protein Few per cell Function responsible for movement

11 Figure 3.6 Proximal structure of bacterial flagella. Filament Direction of rotation during run Rod Peptidoglycan layer (cell wall) Protein rings Cytoplasm Cytoplasmic membrane Filament Gram + Gram Basal body Outer protein rings Rod Integral protein Inner protein rings Integral protein Cytoplasm Outer membrane Peptidoglycan layer Cytoplasmic membrane Cell wall

12 Figure 3.7 Micrographs of basic arrangements of bacterial flagella. Different Arrangement of flagella

13 Figure 3.8 Axial filament. Endoflagella Special form of flagella Axial filament Endoflagella rotate Axial filament rotates around cell Outer membrane Cytoplasmic membrane Spirochete corkscrews and moves forward Axial filament

14 Figure 3.9 Motion of a peritrichous bacterium. 100,000 rpm = 670 miles per hour Positive/Negative taxis Chemo/Photo Movement in response to stimulus = taxis

15 External Structures of Bacterial Cells Fimbriae Structure Nonmotile, rodlike, Sticky, bristlelike projections Shorter than flagella, more numerous Function Used by bacteria to adhere to one another and to substances in environment Serve an important function in biofilms

16 Figure 3.10 Fimbriae. Flagellum Fimbria

17 External Structures of Bacterial Cells Pili - special type of fimbria pili or fimbriae or flagella? Structure What s the difference? Longer than fimbriae but shorter than flagella only have one or two per cell Function Conjugation: Hollow tubes- transfer DNA from one cell to another also called conjugation pili

18 Figure 3.11 Pili. Pilus

19 Bacterial Cell Walls Structure: Scientists describe two basic types of bacterial cell walls Gram-positive and Gram-negative

20 Figure 3.13 Possible structure of peptidoglycan. Sugar backbone Composed of peptidoglycan Tetrapeptide (amino acid) crossbridge Connecting chain of amino acids

21 Bacterial Cell Walls Gram-Positive Bacterial Cell Walls Relatively thick layer of peptidoglycan Contain unique polyalcohols called teichoic acids Appear purple following Gram staining procedure Some gram positive bacteria have up to 60% mycolic acid (waxy lipids) which helps cells survive desiccation called Acid Fast bacteria M. leprae and M. tuberculosis

22 Figure 3.14a 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 Group Activity: using models and text

23 Prokaryotic Cell Walls Gram-Negative Bacterial Cell Walls Have only a thin layer of peptidoglycan Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) Lipid A portion of LPS can cause fever, vasodilation, inflammation, shock, and blood clotting May impede the treatment of disease (OM is protective) Appear pink following Gram staining procedure

24 Figure 3.14b Comparison of cell walls of Gram-positive and Gram-negative bacteria. Porin Outer membrane of cell wall Peptidoglycan layer of cell wall Porin (sectioned) Periplasmic space Gram-negative cell wall Cytoplasmic membrane Lipopolysaccharide (LPS) layer, containing lipid A Integral proteins Phospholipid layers

25 Bacterial Cell Walls Function: 1) provide structure and shape and 2) protect cell from osmotic forces 3) assist some cells in attaching to other cells or 4) in resisting antimicrobial drugs Can target cell wall of bacteria with antibiotics - penicillin

26 shapes

27 Prokaryotic Cell Walls Bacteria Without Cell Walls A few bacteria lack cell walls Mycoplasma pneumoniae Often mistaken for viruses due to small size and lack of cell wall

28 Bacterial Cytoplasmic Membranes Structure Referred to as phospholipid bilayer Composed of lipids and associated proteins Integral proteins Peripheral proteins Fluid mosaic model describes current understanding of membrane structure

29 Figure 3.15 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer. Head, which contains phosphate (hydrophilic) Phospholipid Tail (hydrophobic) Integral proteins Cytoplasm Phospholipid bilayer Integral protein Peripheral protein Integral protein

30 Bacterial Cytoplasmic Membranes Function Energy storage Harvest light energy in photosynthetic bacteria Selectively permeable Naturally impermeable to most substances Proteins allow substances to cross membrane Maintain concentration and electrical gradient

31 Bacterial Cytoplasmic Membranes Function Passive processes Diffusion Facilitated diffusion Osmosis

32 Figure 3.17 Passive processes of movement across a cytoplasmic membrane. Passive=down gradient Gases/alcohol Semi-permeable permease

33 Figure 3.18 Osmosis, the diffusion of water across a semipermeable membrane. Water moves from high to low hypotonic cell

34 Figure 3.19 Effects of isotonic, hypertonic, and hypotonic solutions on cells. Cells without a wall (e.g., mycoplasmas, animal cells) H 2 O H 2 O H 2 O Cell wall Cell wall Cells with a wall (e.g., plants, fungal and bacterial cells) H 2 O H 2 O H 2 O Cell membrane Isotonic solution Cell membrane Hypertonic solution Hypotonic solution

35 Figure 3.19 Effects of isotonic, hypertonic, and hypotonic solutions on cells. Cells without a wall (e.g., mycoplasmas, animal cells) H 2 O H 2 O H 2 O Cell wall Cell wall Cells with a wall (e.g., plants, fungal and bacterial cells) H 2 O H 2 O H 2 O Cell membrane Isotonic solution Cell membrane Hypertonic solution Hypotonic solution

36 Figure 3.19 Effects of isotonic, hypertonic, and hypotonic solutions on cells. Cells without a wall (e.g., mycoplasmas, animal cells) H 2 O H 2 O H 2 O Cell wall Cell wall Cells with a wall (e.g., plants, fungal and bacterial cells) H 2 O H 2 O H 2 O Cell membrane Isotonic solution Cell membrane Hypertonic solution Hypotonic solution

37 Figure 3.19 Effects of isotonic, hypertonic, and hypotonic solutions on cells. H 2 O H 2 O H 2 O Cell wall Cell wall Cells with a wall (e.g., plants, fungal and bacterial cells) H 2 O H 2 O H 2 O Cell membrane Isotonic solution Cell membrane Hypertonic solution Hypotonic solution

38 13) Bacteria of the genus Mycoplasma lack cell walls. What sort of environment do they require for survival? A) low temperature B) hypotonic C) isotonic D) hypertonic E) a biofilm

39 13) Bacteria of the genus Mycoplasma lack cell walls. What sort of environment do they require for survival? A) low temperature B) hypotonic C) isotonic D) hypertonic E) a biofilm

40 Why are patients given saline intravenously when they are dehydrated? What if patients were given normal water Intravenously? Group discussion

41 Prokaryotic Cytoplasmic Membranes Function Active processes Active transport Group translocation Substance is chemically modified during transport

42 Figure 3.20 Mechanisms of active transport. Active=Against gradient Extracellular fluid Uniport Cytoplasmic membrane ATP ATP ADP P ADP P Cytoplasm Uniport Antiport Gated Channels or Ports Symport Coupled transport: uniport and symport

43 Figure 3.21 Group translocation. Glucose Extracellular fluid Very efficient 1 ppm Substance chemically changed PO 4 Cytoplasm Glucose 6-PO 4

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45 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 Magnetospirillum magnetotacticum

46 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

47 Also make endotoxins Present in bacteria which cause anthrax, tetanus, gangrene

48 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

49 Figure 3.26 Representative shapes of archaea. Archae

50 External Structures of Archaea Glycocalyces Function in the formation of biofilms Adhere cells to one another and inanimate objects Flagella Consist of basal body, hook, and filament Numerous differences with bacterial flagella analogous structures Fimbriae and hami Many archaea have fimbriae Some make fimbria-like structures called hami Function to attach archaea to surfaces

51 Figure 3.25 Archaeal hami. Hamus Grappling hook Prickles

52 Archaeal Cell Walls and Cytoplasmic Membranes Most archaea have cell walls Do not have peptidoglycan Contain variety of specialized polysaccharides and proteins All archaea have cytoplasmic membranes Maintain electrical and chemical gradients Control import and export of substances from the cell

53 Cytoplasm of Archaea Archaeal cytoplasm similar to bacterial cytoplasm 70S ribosomes Fibrous cytoskeleton Circular DNA Archaeal cytoplasm also differs from bacterial cytoplasm Different ribosomal proteins Different metabolic enzymes to make RNA Genetic code more similar to eukaryotes

54 Clear-cut differences?

55 Figure 3.3 Typical eukaryotic cell. Nuclear envelope Nuclear pore Nucleolus Cilium Lysosome Mitochondrion Centriole Secretory vesicle Golgi body Transport vesicles Ribosomes Rough endoplasmic reticulum Smooth endoplasmic reticulum Cytoskeleton Cytoplasmic membrane

56 Eukaryotic Cell Walls and Cytoplasmic Membranes Fungi, algae, plants, and some protozoa have cell walls But no glycocalyx and cell walls do not contain peptidoglycan Composed of various polysaccharides Plant cell walls contain cellulose Fungal cell walls composed of cellulose, chitin, and/or glucomannan Algal cell walls composed of a variety of polysaccharides

57 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

58 Eukaryotic Cell Walls and Cytoplasmic Membranes Control movement into and out of cell Do not perform group translocation but endocytosis unique to eukaryotes

59 Figure 3.38 The roles of vesicles in endocytosis and exocytosis. Bacterium Endocytosis (phagocytosis) Phagosome (food vesicle) Vesicle fuses with a lysosome Smooth endoplasmic reticulum (SER) Transport vesicle Lysosome Phagolysosome Golgi body Secretory vesicle Exocytosis (elimination, secretion)

60 Figure 3.29 Endocytosis. Pseudopodium LJYr_JA9Jjd6zhzlkN4OOldkc7gCft9Pa

61 Phagocytosis? Pinocytosis?

62 Figure 3.30a-b Eukaryotic flagella and cilia. Flagellum Cilia

63 Figure 3.6 Proximal structure of bacterial flagella. Filament Direction of rotation during run Rod Peptidoglycan layer (cell wall) Protein rings Cytoplasm Cytoplasmic membrane Filament Gram + Gram Basal body Outer protein rings Rod Integral protein Inner protein rings Integral protein Cytoplasm Outer membrane Peptidoglycan layer Cytoplasmic membrane Cell wall

64 Figure 3.30c Eukaryotic flagella and cilia. Cytoplasmic membrane Cytosol Central pair microtubules Microtubules (doublet) arrangement Cytoplasmic membrane Basal body Portion cut away to show transition area from doublets to triplets and the end of central microtubules Microtubules (triplet) arrangement

65 Cytoplasm of Eukaryotes Flagella Structure and arrangement different from prokaryotic flagella composed of tubulin protein Filaments and basal body; but no hook May be single or multiple; generally found at one pole of cell Function Movement of cell but do not rotate - undulate rhythmically

66 Cytoplasm of Eukaryotes Cilia Structure: Shorter and more numerous than flagella Function: Coordinated beating propels cells through their environment Also used to move substances past the surface of the cell

67 Figure 3.31 Movement of eukaryotic flagella and cilia.

68 Figure 3.30a-b Eukaryotic flagella and cilia. Flagellum Prokaryotic and eukaryotic flagella are different Flagellin/tubulin Rotatary/Side-to-Side movement Basal body structure Membrane bound or not Cilia Only eukaryotes have cilia

69 Eukaryotic ribosome (80S) larger than prokaryotic ribosomes (70S)

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71 Endosymbiotic Theory from 1406

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73 Cytoplasm of Eukaryotes Endosymbiotic Theory Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes Smaller prokaryotes became internal parasites Parasites lost ability to exist independently Larger cell became dependent on parasites for aerobic ATP production Aerobic prokaryotes evolved into mitochondria Similar scenario for origin of chloroplasts Theory is not universally accepted