Cell Structure and Function 2024 PDF

CELL STRUCTURE & FUNCTION CHARACTERISTICS OF LIFE & THEIR DISTRIBUTION IN MICROBES TWO TYPES OF CELLS IN THE WORLD Prokaryotes: Eukaryotes: (No nucleus) (Have a nucleus) Bacteria Fungi Archaea Protozoa Helminths Animals...

CELL STRUCTURE & FUNCTION CHARACTERISTICS OF LIFE & THEIR DISTRIBUTION IN MICROBES TWO TYPES OF CELLS IN THE WORLD Prokaryotes: Eukaryotes: (No nucleus) (Have a nucleus) Bacteria Fungi Archaea Protozoa Helminths Animals Plants, Algae SIMILARITIES BETWEEN PROKARYOTES & EUKARYOTES Similar in their chemical composition cellular entities nucleic acids (DNA and RNA) Proteins similar chemical reactions  metabolism  protein production  energy storage may use flagella for motility  DIFFERENCES BETWEEN PROKARYOTES & EUKARYOTES Prokaryotes Eukaryotes DNA is NOT enclosed by DNA IS enclosed by nuclear membrane membrane  NO NUCLEUS  NUCLEUS IS PRESENT DNA = single circular multiple linear chromosomes chromosome contain various membrane- lack membrane-enclosed enclosed organelles organelles  mitochondria, endoplasmic cell walls (almost always) reticulum, Golgi apparatus, contain peptidoglycan lysosomes, chloroplasts cell division by binary fission if a cell wall is present it DOES NOT contain peptidoglycan  less complex than eukaryotic cell division cell division by mitosis THE PROKARYOTIC CELL  There are 1000’s of species of bacteria!!!  species are identified by: chemical nutritional morphology composition requirements (staining) biochemical energy activities source THE PROKARYOTIC CELL: MORPHOLOGY  Morphology: appearance (morpho = form) size:  0.2-2.0 μm diameter  2.0-8.0 μm length  Most common shapes: cocci, bacilli, spiral  Possible to have other shapes (pleomorphic)  Morphology is hereditary -bacteria are generally monomorphic ↳ Shape a change COCCI Bacilli Spiral (b/wl bacilli + cocci TYPICAL BACTERIAL CELL  GLYCOCALYX Polysaccharide a  Made up of sugar, protein or both  Slime layer: Loosely Polysaccharide Capsule : more virulentl antigenist attached to cell surface ↓ , body Prod entibodies  Sticky layer that allows. Pathogenic  Two types: Icauses disease virulence factor : factors Causing Virulence prokaryotes to attach to surfaces  Water soluble; protects  Capsule: Firmly attached to cell cells from desiccation surface  Protects cells from desiccation S  May prevent bacteria from antiagocutic being recognized & destroyed by host virulent  important in bacterial ↓ virulence (encapsulated vs. unencapsulated)  Presence can be determined by staining (gram ( stain K-Antigen : Capsule bacteria & Prod Capsule, but con to prod Capsule. goin genes from other. bacteria  PROKARYOTIC FLAGELLA  whip-like structures used for motility  filament, hook, basal body  movement by rotation of hook  rotation will push the cell  no membrane/sheath  some bacteria can be identified by their flagellar proteins  eg. E. coli O157:H7  H protein = flagellar protein  eukaryotic flagella: more complex BASIC ARRANGEMENTS OF BACTERIAL FLAGELLA monotrichous amphitrichous lophotrichous peritrichous 1 swarming motility MOTILITY & TAXIS  motility = self-directed movement  series of “runs” and “tumbles” Movement in  chemotaxis, phototaxis response to  Chemicals and light as attractants or repellents a stimulus is termed Positive taxis: Movement toward an attractant “Taxis” Negative taxis: Movement away from a repellent  AXIAL FILAMENTS  Similar to flagella but wrap around the cell  found only on spirochetes  “corkscrew”-like movement *  also called “endoflagellum” corkskrew movement lyme disease · Axial Silaments  FIMBRIAE & PILI  short, hairlike appendages  shorter, straighter & thinner than flagella  Fimbriae: Sticky, bristle-like projections used by bacteria to adhere to one another, to hosts, and to environment substances  Shorter than flagella; >100s/cell  Serve important function in biofilms for adherence to various surfaces  N. gonorrhoeae: attach to mucous membranes  Pili: Tubules composed of pilin, adhesins  Longer than fimbriae, shorter than flagella  Bacteria typically only have 1-2 per cell  mediate the transfer of DNA from one cell to another (conjugation) used to transfer genetic materials biwl bacteria  F pili as conjugation or sex pili  The ordinary pili mediate adhesion to mucous membranes  CELL WALL  surrounds plasma membrane  semi-rigid, responsible for cell shape  complex structure: Peptidoglycan  shields cell interior from environmental changes  protects against changes in water pressure (osmosis)  Significance of bacterial cell wall: good drugs harm the invader but not the host bacterial cell wall very different from host cell  PEPTIDOGLYCAN  Peptidoglycan composed of sugars:  N-acetylglucosamine (NAG)  N-acetylmuramic acid (NAM) Chains of NAG and NAM attached to other chains by tetrapeptide crossbridges I – bridges may be covalently bonded to one another – bridges held together by short connecting chains of amino acids enzymes Penicillin interferes W/ Crosslinking WI NAG & NAM A A.. Only Onests to nam GRAM POSITIVE & GRAM-NEGATIVE BACTERIA  Cell wall composition is important in differentiating bacteria  Scientists describe 2 main types of bacterial cell walls based on cell wall characteristics:  Bacteria are generally Gram positive or Gram negative Bacteria Gram- Gram- positive negative *  Gram stain is usually the first test used to help narrow down possible Gram stain is used only for bacteria  GRAM-POSITIVE CELL WALL  Contain many layers of peptidoglycan  Contain teichoic acids and lipoteichoic acids  Wall is thick and rigid  less sensitive to mechanical damage than Gram -ve  more sensitive to penicillin than Gram -ve GRAM-NEGATIVE CELL WALL “Peptidoglycan sandwich”: – Outer membrane + Peptidoglycan (thin layer) + Plasma membrane Outer Membrane: negative charge, avoid host cell phagocytosis barrier against antibiotics, lysozyme, other chemicals porins allows nutrients in lipopolysaccharide (LPS) = endotoxin 3 components fever, shock Causes : Opntigen > - endotoxin only in Gram-ve > - core antigen ↓ (toxic Lipid A ATYPICAL CELL WALLS (EXCEPTIONS)  Mycoplasma: Bacterial genus that naturally lacks cell walls  Cannot be Gram stained  Mycobacteria: Bacterial genus that has an abundance of mycolic acids in the cell wall Cannot be Gram stained  Corynebacterium and Nocardia also produce mycolic acids Weakly Acid fast  Archaea: Lack peptidoglycan, instead have pseudomurein  ↑ gram stain 62 d absorbestal Violet Grant bacteria appears blue/purple CO2 they retain Crystal Violet Co2 of their thick cen was Gram-2 Due to a cen wall ↓ l yes use , gram stain appears test is retain Violet Pink/red Pigment  PLASMA MEMBRANE  cytoplasmic membrane, inside of cell wall, encloses cytoplasm  phospholipid bilayer: composed of lipids and proteins  Fluid mosaic model describes membrane structure  approximately half composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels  integral proteins, peripheral proteins, glycoproteins  Main Functions: controls what enters cell by selective permeability, pores, transporters home of machinery for energy production, nutrient breakdown  MOVEMENT ACROSS PLASMA MEMBRANE Passive processes: Simple diffusion, facilitated diffusion, osmosis  SIMPLE & FACILITATED DIFFUSION  It is easier to move substances from areas of HIGH concentration to areas of LOW concentration  down a concentration gradient Simple Diffusion Facilitated Diffusion transported outside substance (solute) transporter protein plasma membrane inside  OSMOSIS  net movement of SOLVENT molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher of higher solute concentration.  solvent (H2O) moves from high  low concentration TONICITY Isotonic solution: Hypertonic solution: Hypotonic solution: Solution with Solution has a Solution has a equal osmotic higher [solute] than lower [solute] than pressure across an isotonic solution an isotonic solution cell membrane  ACTIVE TRANSPORT Material moves from low to high concentration by transporter proteins Useful when bacterial cell is in environment with low [nutrients]  cell uses an active process to gain needed substances Cell expends energy to go against the concentration gradient  CYTOPLASM  cytosol = liquid portion of cytoplasm  80% H2O  proteins, enzymes, carbohydrates, lipids, inorganic ions, low MW compounds, inorganic ions include:  nucleoid area: DNA  ribosomes: sites of protein synthesis  inclusions: reserve chemical deposits  NUCLEOID Not membrane enclosed nuclear area contains genetic information  bacterial chromosome: single circular dsDNA, no proteins (d histones( 3e complex into organization chromosomes  compare: eukaryotes have multiple linear chromosomes carries all information required for the cell’s structure and function up to 20% of cell volume in actively growing bacteria  PLASMIDS  “extrachromosomal” genetic elements  replicate independently of main chromosome plasmid  contain genes not crucial to survival  antibiotic resistance > - production of enzymes Ce lactamase destroy. g. :  tolerance to toxic elements Penicillin = enterotoxin neurotoxin alphatoxin , etc , ,.  toxin production  can be transferred from one bacteria to another  RIBOSOMES  site of protein synthesis  prokaryotic and eukaryotic ribosomes ribosomes are different  Prokaryotic = 70S  some antibiotics inhibit prokaryotic ribosomes  with no effect on eukaryotic ribosomes 50s 30s Gros  ENDOSPORES  Unique resting structures produced by some bacteria  a defensive strategy for survival against unfavorable adverse environmental conditions  not metabolically active  Highly durable, dehydrated cells, thick walls  Survive heat (boiling), dehydration, toxic chemicals, radiation, etc  problem in food industry (under processing)  Located terminally, sub-terminally or centrally in cells Unique to certain bacteria tetoni - Clostridium sp. - - botulinum perfringens - difficile Anthracis ~ Bacillus sp. & cereus (reneated rice ( Formation of Endospores by Sporulation Produce toxin ! State into body thru trauma (wound) a get out of Vegetative + Con get , Tetanus , onthrax : THE EUKARYOTIC CELL  actin filament : flagellum microtubule : Flagella FLAGELLA & CILIA  Flagella: few, long relative to cell size  shaft composed of arranged tubulin (microtubules)  “9+2” microtubule arrangement in flagellated eukaryotes  may be single or multiple; generally found at one pole of cell  Cilia: numerous, short (like hairs)  shorter and more numerous than flagella  composed of tubulin: “9+2” & “9+0” arrangements  coordinated beating propels cells through their environment  also used to move substances past the cell surface with wave-like movement  ciliated cells in respiratory tract ↳: Flagella  CELL WALL AND GLYCOCALYX  No peptidoglycan in eukaryotic cell walls!  clinically significant  much simpler than prokaryotic cell wall  made of carbohydrates (sugars)  algae: cellulose  fungi: chitin  yeast: glucan and mannan  protozoa: no typical cell wall; flexible outer coating called a pellicle  animal cells: glycocalyx – layer of sticky carbohydrates to strengthen cells and provide means of adherence to other cells PLASMA MEMBRANE  see prokaryotic plasma membrane  like prokaryotic plasma membrane has a phospholipid bilayer containing proteins  contain carbohydrates attached to proteins and sterols  have similar passive and active processes to move materials across plasma membrane  CYTOPLASM & ORGANELLES  Cytoplasm: inside of plasma membrane, outside of nucleus  Very complex internal structure: Cytoskeleton  Important functions: support, shape, intracellular transport, cellular movement, phagocytosis  Contains ribosomes that are larger and denser (80S) than prokaryotic ribosomes  Contains membrane-bound organelles  Organelles: characteristic of eukaryotic cells  Structures w/ specific shapes and specialized functions  Nucleus, Smooth and Rough Endoplasmic Reticulum, Golgi, Lysosomes, Peroxisomes, Mitochondria  NUCLEUS  characteristic of eukaryotes  often largest cellular structure  contains DNA  DNA associated with proteins  Chromatin = DNA + proteins  linear chromosomes  surrounded by nuclear envelope:  double membrane composed of two phospholipid bilayers  nuclear envelope contains nuclear pores  ENDOPLASMIC RETICULUM network of flattened sacs/ tubules connected to nuclear envelope rough ER:  coated in 80S eukaryotic ribosomes  protein synthesis and transport smooth ER:  no ribosomes  functions: lipid synthesis, glycogen breakdown, store Ca2+, detoxification RIBOSOMES  GOLGI COMPLEX  proteins from rough ER are sorted in Golgi  Golgi complex consists of flattened sacs called cisterns  Functions in membrane formation and protein secretion VESICLES, LYSOSOMES & PEROXISOMES  Vesicles: store and transfer substances within cells  May store nutrients in cell  Lysosomes: contain catabolic enzymes capable of digesting bacteria  important in host immune response  WBC have lots of lysosomes  Peroxisomes: contain enzymes that degrade poisonous wastes  MITOCHONDRIA Have two membranes composed of phospholipid bilayer Produce most of cell’s energy (ATP): “powerhouses” of the cell Interior matrix contains their own DNA & ribosomes: 70S ribosomes more like prokaryotic than eukaryotic circular molecule of dsDNA reproduce like bacterial cells by binary fission COMPARISON: PROKARYOTIC & EUKARYOTIC CELLS Which of the following is not a function of a glycocalyx? a. It forms pseudopods for faster mobility of an organism. b. It can protect a bacterial cell from drying out. c. It hides a bacterial cell from other cells. d. It allows a bacterium to stick to a host Which of the following statements is true? a. The cell walls of bacteria are composed of peptidoglycan. b. Peptidoglycan is a fatty acid. c. Gram-positive bacterial walls have a relatively thin layer of peptidoglycan anchored to the cytoplasmic membrane by teichoic acids. d. Peptidoglycan is found mainly in the cell walls of fungi, algae, and plants Which of the following is not associated with prokaryotic organisms? a. nucleoid b. glycocalyx c. cilia d. circular DNA