Ch 4 - Functional Anatomy Of Prokaryotic And

8/28/2016Prokaryotic cellsFunctional Anatomy of Prokaryoticand Eukaryotic CellsChapter 4BIO 220 DNA circular (usually) and not enclosed withina nucleus DNA not associated with histones Generally lack membrane-enclosed organelles Cell wall contains peptidoglycan (usually) Divide by binary fissionBinary fissionFig. 6.12Fig. 10.11

8/28/2016Size, shape, and arrangement ofbacterial cells Shape coccus (cocci)Fig. 4.1Size, shape, and arrangement ofbacterial cells Shape bacillus (bacilli)Fig. 4.2Size, shape, and arrangement ofbacterial cells Shape spiral Vibrio – curved rods– Vibrio cholerae Spirilla – use flagellaBacterial cell shape is dependent on Genetics– Most bacteria are monomorphic – keep sameshape– Some are pleomorphic – can change shape– Campylobacter jejuni Spirochetes – axialfilaments– Borrelia burgdorferiFig. 4.42

8/28/2016Prokaryotic cell structure Structures external to cell wallStructures external to cell wall Cell wall Structures internal to cell wallGlycocalyx “Sugar coat” of cell The glycocalyx is a viscous, gelatinous layerlocated outside the cell wall that is composedof polysaccharides and/or polypeptides If it appears organized and firmly adheres to theoutside of the cell wall it is called a capsule If instead it is unorganized in appearance andmore loosely attached to the cell wall it is calleda slime layerFig. 4.63

8/28/2016Glycocalyx functions Allows certain bacteria to resist phagocyticengulfment– Blocks the ability of phagocytes to recognizeantigenic cell wall components (LPS, peptidoglycan)– i.e. Streptococcus pneumoniae, Bacillus anthracisGlycocalyx functions Helps protect cells against dehydration Helps trap nutrients in bacterial cells Allows some bacteria to adhere toenvironmental surfaces– Biofilm formation– i.e. Streptococcus mutans, Vibrio choleraeFlagella Used for motility Flagellar arrangements include atrichous,peritrichous, polar (monotrichous,lophotrichous, amphitrichous)Parts of a flagellum Filament– Composed of globular protein (flagellin)– H antigens help distinguish between serovars(variations within a species) of gram (-) bacteria Hook– Attaches filament to cell Basal body– Anchors flagellum to cell wall and plasmamembraneFig. 4.74

8/28/2016Prokaryotic flagella Move like a propeller (rotates from basalbody), whereas eukaryotic flagella move like awhip Not covered by membrane Motility patterns– Runs – bacterium moves in one direction for aperiod of time (moves 10-20 times its length)– Tumbles – periodic, abrupt, random changes indirectionFig. 4.8Runs and tumblesTaxis Movement of a bacterium toward or awayfrom a particular stimulus is called taxis Chemotaxis PhototaxisFig. 4.9a5

8/28/2016Axial filamentsFimbriae Spirochetes use axialfilaments for motility Axial filaments aresimilar to flagella,except that theywrap around the cellbeneath an outersheath Spirochetes move ina spiral fashion Some gram-negative bacteria have hair-likeappendages (pilin) arranged around a centralcore Fimbriae can occur on cell poles or along cellsurface, may be few to several hundred Fimbriae adhere to each other and to surfacesin and out of the body Neisseria gonorrhoeae,Escherichia coliFig. 4.11Pili Longer than fimbriae and only a few per cell Involved in motility– Twitching (grappling hook) and gliding motilityCell wall Involved in DNA transfer– Conjugation6

8/28/2016Cell wall functions Prevent osmotic lysis of bacterial cells Helps maintain shape of bacterium Point of anchorage for flagella (when present)Fig. 4.6Cell wall compositionPeptidogycan (murein)Peptidoglycan –composed of repeatingdisaccharide subunitsconnected bypolypeptidesFig. 4.12Fig. 4.13a7

8/28/2016Cell wall: gram – positive bacteriaGram – positive cell wall Thick peptidoglycan layer (many layers) Contain teichoic acids (alcohol phosphate)– Lipoteichoic acid – spans the peptidoglycan layerand is linked to the plasma membrane– Wall teichoic acid – linked to peptidoglcan– May regulate transport of cations in/out of cells,role in cell growth, provide much of the cell wall’santigenic specificity Granular layer contains lipoteichoic acid,enzymesFig. 4.13bCell wall: gram – negative bacteria Thin peptidoglycan layer and an outermembraneOuter membrane (OM) Lipopolysaccharides (LPS), lipoproteins,phospholipids LPS has three parts:– Lipid A – embedded in outer layer of OM– Core polysaccharide – structural role– O polysaccharide – antigenic Lipoproteins – anchor peptidoglycan to OM Porins permit the passage of molecules such asnucleotides, disaccharides, peptides, amino acids,B12 and iron Presence of OM helps bacteria evade complementand phagocytosisFig. 4.13c8

8/28/2016Gram staining Why do we see differences in how gram ( )and gram (-) bacteria appear with the gramstaining protocol? Gram stain protocol– Primary stain – crystal violet– Grams iodine– Decolorizer– Counterstain – safraninMycoplasma (pneumoniae)Fig. 11.249

8/28/2016Acid-fast cell walls Used to identify the bacteria of the genus . . .Structures internal to the cell wall Cell walls contain a high concentration of ahydrophobic waxy lipid (mycolic acid)surrounding a thin layer of peptidoglycanPlasma membranePlasma membrane functions Selective permeability Breakdown of nutrients and the production ofenergyFig. 4.14Fig. 4.1510

8/28/2016Simple diffusionPM transport Passive transport– Simple diffusion– Facilitated diffusion– Osmosis Active transport– Group translocationFig. 4.16Facilitated diffusionFig. 4.17OsmosisFig. 4.1711

8/28/2016Active transport Requires the use of energy In group translocation, as a substance istransported across the wall of a prokaryoticcell, the substance is chemically altered whicheffectively traps it within the cellFig. 4.18CytoplasmCytoplasm Thick, aqueous, semitransparent, and elastic Nucleoid Mostly water, but also contains proteins,CHOs, lipids, inorganic ions Ribosomes Inclusions Cytoskeleton present, but made of differentproteins from those found in eukaryotic cells(MreB and ParM, cresetin, FtsZ)12

8/28/2016Nucleoid Lacks a nuclearenvelope Contains bacterialchromosome Plasmids – small,circular dsDNA thatreplicatesindependently ofbacterial chromosomeRibosomes What is the function of ribosomes? Ribosomal subunitsFig. 4.6Fig. 4.19Inclusions Metachromatic granules (volutin)– Reserve of inorganic phosphate for ATP synthesis– Corynebacterium diphtheriae Polysaccharide granules Lipid inclusions– Mycobacterium, Bacillus, SpirillumInclusions Carboxysomes– Ribulose 1,5-diphosphate carboxylase Gas vacuoles Magnetosomes– Fe3SO4– Magnetospirillum Sulfur granules– AcidithiobacillusFig. 4.2013

8/28/2016Sporulation (sporogenesis)Endospores Members of Clostridium and Bacillus can formendospores, which are essentially dehydrated,stripped-down, “resting” bacterial cells When released into the environment,endospores can survive extremes in heat,hydration, toxic chemical and radiationexposureFig. 4.21Endospores Contain a large amount of dipicolinic acid(DPA), which may serve to protect bacterialDNA Endospore core contains DNA, a little RNA,ribosomes, enzymes, small molecules Germination is the process by which anendospore returns to its vegetative state Germination is triggered by high heat ormolecules called germinants (alanine &inosine)Endospores – Why should I care? Home canning – botulism– Clostridium botulinum14

8/28/2016Eukaryotic cells DNA organized into chromosomes containedwithin a nucleus DNA is associated with histones Do have membrane-enclosed organelles Cell walls lack peptidoglycan Cell division by mitosis/meiosis andcytokinesisFig. 4.22Cilia and FlagellaCell wall and glycocalyx When present, tend to be simpler thanprokaryotic cell walls and have a differentcomposition Algae & plants – cellulose Fungi – cellulose or chitin Yeasts – polysaccharides (mannan and glucan) Protozoa have an outer protein covering calleda pellicle GlycocalyxFig. 4.2315

8/28/2016Plasma membrane Similar to prokaryotes Eukaryotic membranes contain carbohydratesand sterols Plasma membrane transport– No group translocationCytoplasm Everything inside the plasma membrane withthe exception of the nucleus Cytosol vs. cytoplasm Cytoskeleton Cytoplasmic streamingRibosomesNucleus Sites of protein production 80S (60S & 40S) vs 70S May be free or attached to ER PolyribosomesFig. 4.2416

8/28/2016Endoplasmic reticulumFig. 4.25Golgi complex & LysosomesFig. 4.26Vacuoles (Plants) MitochondriaDerived from Golgi complexMay serve as temporary storage organellesHelp bring food into the cellStorage of wastesMay accumulate waterFig. 4.2717

8/28/2016Peroxisomes and centrosomesChloroplasts (Algae green plants)Fig. 4.28Fig. 4.22Endosymbiotic theory Origin of eukaryotic cells Ancestral eukaryotic cell developed a“nucleus” when PM folded around DNA This cell likely ingested aerobic bacteria Support– Mitochondria/chloroplasts resemble bacteria– These organelles contain circular DNA– Organelles reproduce independently– Ribosomes resemble those of prokaryotes– Antibiotic action18

Functional Anatomy of Prokaryotic and Eukaryotic Cells Chapter 4 BIO 220 Prokaryotic cells DNA circular (usually) and not enclosed within a nucleus DNA not associated with histones Generally lack membrane-enclosed organelles Cell wall contains peptidoglycan (usually) Divide by binary fission Binary fission Fig. 6.12 Fig. 10.1