MIC 205 - Microbiology - Prokaryotic Cell Structure PDF

MIC 205 - Microbiology Lecture 3: My Itty-Bitty Bits and Pieces Ch. 3 Cell Structure and Function Lecturer: Patrick Daydif Office: UCENT 356 Phone: (602) 496-0599 Email: [email protected] Office Hours: Refer to Canvas (or by appointment) The bes...

MIC 205 - Microbiology Lecture 3: My Itty-Bitty Bits and Pieces Ch. 3 Cell Structure and Function Lecturer: Patrick Daydif Office: UCENT 356 Phone: (602) 496-0599 Email: [email protected] Office Hours: Refer to Canvas (or by appointment) The best way to contact me and answer your questions is Face to Face. 1 Chapter 3::Features of Prokaryotic Cells 3 Prokaryotes Do not have a membrane surrounding their DNA; no nucleus Lack various internal membrane-bound structures Small; ~1.0 μm in diameter Simple structure Comprised of bacteria and archaea 4 1  External Structures of Prokaryotes Glycocalyces – Capsule – Slime Layer Flagella Fimbriae and Pili 5 Glycocalyces Gelatinous, sticky substance surrounding the outside of the cell Composed of polysaccharides, polypeptides, or both Protects cells from desiccation (drying out) Prevent bacteria from being recognized Prevent bacteria from and destroyed by the Immune system Two types of Glycocalyces Capsules Firmly attached to the cell’s surface Slime layers Loosely attached to the cell’s surface Sticky layer that allows prokaryotes to attach to surfaces 6 Flagella Responsible for movement Long, whiplike tail structures that extend beyond the surface of the cell Complex molecular machines that often translate rotary motion into directional movements 7 2  Flagellar Structure Composed of filament, hook, and basal body Flagellin protein (filament) arranged in chains and forms a helix around a hollow core Base of filament inserts into a hook Basal body anchor filament and hook to the cell wall by a rod and a series of either two or four rings Filament rotates 360º to generate forces needed for propulsion 8 Arrangements of Flagella Monotrichous – single flagellum at only one end of the cell Lophotrichous – multiple flagella grouped at one end of the cell 9 Arrangements of Flagella Amphitrichous – single or multiple flagella at both ends of the cell Endoflagella – special flagella found on spirochetes that enable “corkscrew” motion Peritrichous – multiple flagella covering the entire cell 10 3  Function of Flagella Rotation propels bacterium through the environment Rotation can be clockwise or counterclockwise; in some species, rotation is reversible Prokaryotes move in response to stimuli (taxis) – Runs – movements of cell in a single direction; increase with favorable stimuli (positive chemotaxis and/or phototaxis) – Tumbles – abrupt, random, changes in direction; increase with unfavorable stimuli (negative chemotaxis and/or phototaxis) 11 Nonmotile Extensions Fimbriae – Sticky, proteinaceous, bristlelike projections – Used by bacteria to adhere to one another, to hosts, and substances in the environment – May be hundreds per cell and are shorter than flagella – Serve an important function in biofilms Pili – Long hollow tubules composed of pilin – Longer than fimbriae but shorter than flagella – Bacteria typically only have one or two per cell – Joins two bacterial cells and mediate the transfer of DNA from one cell to another (conjugation) – Also known as conjugation pili or sex pili 12 Fimbriae v. Flagella 13 4  Pilus v. Fimbriae 14 Prokaryotic Cell Walls Prokaryotic cells – Bacteria: Most have a cell wall composed of peptidoglycan; a few lacks a cell wall entirely – Archaea: Have different cell wall chemistry Function: – Provides structure and shape – Protects cell from osmotic forces – Assists some cells in attaching to other cells or in eluding antimicrobial drugs 15 Bacterial Cell Walls Peptidoglycan is composed of peptide-linked chains of polysaccharides (lattice) – Polysaccharide portions consist of chains of two alternating sugars... N-acetylglucosamine (NAG) N-acetylmuranic acid (NAM) – Chains of NAG and NAM are linked to each other by the tetrapeptide cross-bridge (four amino acids) Bridges may be covalently bonded to one another (Unique Enzyme) NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM cross bridge NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM NAG NAM 17 5  Bacterial Cell Walls 18 Gram-Positive Cell Walls Thick layer of peptidoglycan (~40 layers)! Retains crystal violet dye in Gram staining procedure, causing cells to appear purple 19 Gram-Negative Cell Walls Thin layer of peptidoglycan (~10 layers)! Also possess a bilayer membrane (Outer Membrane) composed of phospholipids, channel proteins (porins), and lipopolysaccharide (LPS) Cells appear pink due to safranin dye in the Gram staining procedure 20 6  Comparisons of Gram +/- Cells Gram positive cells Gram negative cells – Inner (plasma) – Inner (plasma) membrane membrane – Thick layer of – Thin layer of peptidoglycan peptidoglycan – No outer membrane – Outer membrane – Gram stain (LPS) Purple (crystal – Gram stain violet) Pink (safranin) Many important antibiotics are inhibitors of peptidoglycan synthesis!!! 21 Prokaryotic Cell Membrane Referred to as phospholipid bilayer; composed of lipids and associated proteins Approximately half the membrane is composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels – Integral proteins – Peripheral proteins – Glycoproteins Fluid mosaic model describes the current understanding of membrane structure 23 Cell Membrane Structure 24 7  Cell Membrane Function Controls passage of substances into and out of the cell; selectively permeable Harvests light energy in photosynthetic bacteria Functions in energy production (ETC) – Maintains a concentration gradient and electrical gradient; collectively known as an electrochemical gradient Transport across the cell membrane – Membrane is naturally impermeable to most substances – Proteins are required for some substances to cross the membrane – Transport occurs by passive or active processes 25 Passive Transport No energy (ATP) needed Molecules move from high concentration to low concentration Types – Simple diffusion Small, uncharged molecules Osmosis – simple diffusion of water Solution conditions can be described as isotonic, hypertonic, or hypotonic – Facilitated Diffusion Requires a protein carrier or a protein channel Large and charged molecules 26 Active Transport In active transport, carrier proteins in the membrane hydrolysis ATP (ATP→ADP) to move molecules against their concentration gradients Types of carrier proteins – Uniporters – single-molecule transport – Antiporters – coordinated transport of multiple molecules in opposite directions – Symporters – coordinated transport of molecules in the same direction 27 8  Cytoplasm of Prokaryotes Consists of all intracellular materials confined within the cell membrane The term “cytosol” refers to the liquid portions of the cytoplasm Key components... – Biological Molecules - Carbohydrates, Lipids, Proteins… – Inclusions – may include reserve deposits of chemicals – Ribosomes – sites of protein synthesis (more later) – Cytoskeleton – plays a role in forming the cell’s basic shape (This is NOT similar to eukaryote cells) – Enzymes- catalysts chemical reactions – DNA/RNA - genetic information (more later) – Metabolic cycles – TCA, Glycolysis, TXC, TXL…….. 28 Eukaryotes Larger; 10-100 μm in diameter More complex structure Have membrane surrounding DNA; have a nucleus Have internal membrane-bound organelles Comprised of algae, protozoa, fungi, animals, and plants 31 Features of Eukaryotic Cells 32 9  Eukaryotic cells: Structure & Function Component: Structure & Function Extracellular Matrices: anchor to surface/ strengthens cell surface Flagella: Movement Cilia: Movement/ move substances past the surface of the cell Cell Walls: polysaccharides/ with a rigid structure Cell Membranes: Same as bacterial cells, but different lipids. Nucleus: Houses DNA Ribosomes: Sites for protein synthesis (Larger than prokaryotic ribosomes 80S versus 70S) Endoplasmic Reticulum (ER): Synthesis platform, preliminary processing plant, and transport system for proteins and lipids Mitochondria: produce most of the cell’s ATP Chloroplasts: Light-harvesting structures for making ATP 33 External Structures of Eukaryotes Extracellular Matrix (ECM) Flagella Cilia 45 Extracellular Matrices Comparable to prokaryotic glycocalyces, but never as organized as bacterial capsules Helps animal cells anchor themselves to substrates and/or adhere to each other Strengthens cell surface and protects the underlying fluid cell membrane Provides protection against dehydration (desiccation) Play important roles in cell-to-cell recognition and communication 46 10  Structure of Eukaryotic Flagella and Cilia 47 Flagella In all flagellated eukaryotes, flagellar shaft composed of “9 + 2” arrangement of microtubule filaments Microtubules are composed of tubulin protein Eukaryotic flagella lack a hook; microtubule filaments instead are anchored directly to the cell by basal body Basal body has a “9 + 0.” arrangement of microtubules May be single or multiple Do not rotate but undulate rhythmically Eukaryotic flagella actually reside inside the cell 48 Flagella Comparisons Prokaryotes Eukaryotes Filament is a hollow tube Shaft is a solid “9 + 2” array composed of helical chains of of microtubule filaments flagellin protein made of tubulin protein Hook structure anchors No hook – shaft is anchored filament to the basal body directly to the basal body Basal body is series of one or Basal body is a special “9 + 0” more protein disks array of microtubules Reversible, rotational motion Undulatory “wave-like” that determines run versus motion, not rotation tumble behaviors Reside inside the cell due to True external structures cell membrane sheath 49 11  Cilia Shorter and more numerous than flagella Composed of both “9 + 2” and “9 + 0” arrangements of microtubules Coordinated beating functions to propel cells through their environment Ciliary action also functions to move substances past the surface of the cell for nutrient uptake (feeding) 50 Eukaryotic Cell Walls Fungi, algae, and plants have cell walls but no extra- cellular matrices (ECMs) Composed primarily of polysaccharides that vary by cell type... – Plant cell walls mostly contain cellulose – Fungal cell walls composed of chitin, cellulose, and/or glucomannan – Algal cell walls composed of cellulose, agar, carrageenan, silicates, algin, calcium carbonate, or a combination of these Permeable to water and most small metabolites, but not organic macromolecules (e.g., antibodies) Provide multicellular eukaryotes with a rigid structure that counteracts gravity (think cellular exoskeleton) 51 Eukaryotic Cell Membranes Fluid mosaic boundary composed of phospholipids and peripheral and integral proteins Contains cholesterol and other steroid-derived lipids for dynamic maintenance of membrane fluidity Controls movement of materials into and out of the cell through... – Passive and facilitated diffusion, osmosis, and active transport – Endocytosis – invagination of membrane engulfs extracellular materials for import (e.g., amoebas and macrophages) – Exocytosis – evagination of membrane expels intracellular materials for export 52 12  Cytoplasm of Eukaryotes Consists of all non-nuclear intracellular components, including membrane-bound organelles, confined within the cell membrane Here, “cytosol” refers to the non-organellar liquid portions of the cytoplasm Organelles fall into two categories... – Nonmembranous – ribosomes, cytoskeleton, centrioles, and centrosome – Membranous – nucleus, endoplasmic reticulum, golgi bodies, lysosomes, peroxisomes, vacuoles, vesicles, mitochondria, chloroplasts 53 Cytoskeleton Extensive network of structural filaments and cables that function to... – Provide overall shape and anchor organelles in specific positions – Move organelles and cytoplasmic contents (streaming) – Contract or expand regions of the cell membrane during endocytosis, exocytosis, and amoeboid movement Three main structural elements – Microtubules composed of tubulin protein – Microfilaments composed of actin protein – Intermediate filaments composed of various proteins 54 Cytoskeleton 55 13  Ribosomes Larger than prokaryotic ribosomes (80S versus 70S) – “S” refers to a “Svedberg” or “sedimentation coefficient,” a unit that defines the relative size of a macromolecule based upon how quickly it sediments out of solution in a centrifuge Composed of RNA and protein molecules that assemble into 60S and 40S subunits Critically important sites for protein synthesis – Decoding of genetic information via “translation” – conversion of nucleotide code into a specific string of amino acids – Joining of amino acids into unfolded, immature proteins Many important antibiotics are ribosomal inhibitors!!! 56 Nucleus Usually the largest, most obvious organelle in the cell Contains most of the cell’s DNA Surrounded by the nuclear envelope, a double membrane composed of two phospholipid bilayers Nuclear envelope contains nuclear pore complexes that are large enough to allow passage of intact macromolecules (proteins!) 57 Endoplasmic Reticulum (ER) Mesh-like arrangement of hollow sacs and tubules that are continuous with the nuclear envelope Synthesis platform, preliminary processing plant, and transport system for proteins and lipids Two major forms... – Smooth endoplasmic reticulum (SER) – plays a role in lipid synthesis – Rough endoplasmic reticulum (RER) – ribosomes attached to the outer surface; transports proteins produced by ribo- somes to Golgi bodies 58 14  Golgi Bodies In most cells, consists of flattened hollow sacs that are surrounded by single phospholipid bilayers Receives, processes, and packages immature proteins for transport to the cell membrane and subsequent export from the cell – Processing involves theaddition and subtraction of sugars for glycoprotein synthesis – Packaging involves inserting molecules into secretory vesicles that later fuse with the cell membrane during exocytosis 59 Summary of Endomembrane System Network of membranes that are continuous with the nuclear envelope; includes smooth ER, rough ER, Golgi bodies, and lysosomes. 60 Mitochondria Like nucleus, possess two boundary membranes that are composed of two separate phospholipid bilayers Functions to produce most of the cell’s ATP Interior compartment contains a circular molecule of DNA (mitochondrial chromosome) and 70S ribosomes 61 15  Chloroplasts Possess two boundary membranes that are composed of two separate phospholipid bilayers Light-harvesting structures found in photosynthetic eukaryotes (algae and plants) that function to store light energy as reducing equivalents for ATP synthesis Interior compartment contains a chloroplast chromosome and 70S ribosomes 62 Other Important Organelles Lysosomes contain catabolic enzymes within acidic interiors for breaking down cellular garbage and contaminants Peroxisomes contain enzymes that degrade poisonous wastes; significant in oilseed plants for converting storage oils into energy for post-germinative growth Vacuoles and vesicles respectively store and transfer chemicals and nutrients within cells 63 Passive Transport Implications 64 16  The Cell as a Factory 65 Lecture Task “Process of Life “ What are the monomer units/ building blocks of the following molecules? – Protein – DNA – Lipid – Polysaccharides – Polypeptides – Glycoproteins Martian meteorite ALH 84001 Collection for grade? Possible (5 points) 66 Process of Life How do we know if something is “alive”? – – – – – – Structural components of living organisms must be equipped to perform these “life” functions! Martian meteorite ALH 84001 67 17