MICRO Block 3

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what features do all cells have in common

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154 Terms

1

what features do all cells have in common

cytoplasm; cytoplasmic cell membrane; ribosomes; cell wall (some microbes- strength)

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properties of all cells

structure, metabolism, growth (proteins convert nutrients into new cells) , evolution (chance mutations in the DNA)

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metabolism in all cells

all cells use information in DNA to produce RNA and protein. via catabolism and anabolism

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catabolism

transforming molecules to produce energy

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anabolism

synthesising macromolecules

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properties of certain cells

communication; motility, horizontal gene transfer; differentiation

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size range of prokaryotes

0.2 µm to >600 µm in diameter and between 0.5 µm and 10 µm long

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size range of eukaryotes

5-100 micrometers

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how is surface area to volume ratio an advantage in smaller cells

small cells have a higher SA:V ratio and support greater nutrient and waste product exchange per unit cell volume, making them more efficient than larger cells.

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coenocytic fungi

aseptate fungi- no septa; continuous cell mass with 100 000s nuclei

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Four Kingdoms of Eukarya

Protista, Fungi, Plantae, Animalia

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characteristics of algae

  • cell walls with cellulose

  • can photosynthesize

  • many conformations

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fungi

Unicelllular/ multicelllular

  • cell walls contain chitin -derive nutrients from environment

  • non motile usually

  • asexual (budding/fission)/ sexual (meiosis derived spores) reproduction

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protozoa

unicellular asexual/sexual reproduction nutrition from organic substances movement through cilia, flagella, pseudopods

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viruses

obligate parasites; only replicate in host cell do not carry out metabolism small genomes of DNA /RNA

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extremophiles

live in extreme environments

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beginning of microscopy

Robert hooke- first to describe microbes Antoni van leeuwenhook- first to see bacteria

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light microscopy

passing visible light transmitted or reflected from the sample through one or multiple lenses to magnify the sample.

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bright field microscopy

simplest of all light microscopy which uses white light to illuminate the object

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three main parts of compound microscope

mechanical- base, arm stage magnifying- objective and ocular lens illuminating - substage condenser, iris, diaphragm, light source

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total maginification formula

ocular x objective lens

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spherical abberation

found in systems that use spherical lenses; light rays striking off centre are ore or less refracted than those at the centre blurring of the image

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chromatic aberrations

fringes of colour around the image caused by dispersion of lens material

  • variation of refractive index with wavelength of light

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resolving power

ability to measure separation of images close together

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numerical aperture

the ability of a lens to gather light

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how does oil change the RI of transmitted light

-increases resolving power of a microscope -oils have high RI

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Resolution limit

minimum angular separation between two points that can be perceived

  • d=0.5 x λ/ NA

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NA for dry and oil immersion

Dry-0.95 Oil- 1.5

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basic dyes

stain cation

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acidic dyes

stain anions

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simple stains

single basic dye -highlights entire microorganism -crystal violet, safranin, methylene blue

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mordant

additive that increases affinity of stain to sample

  • eg grams iodine stain, forms crystal violet-iodine complex which clumps and is contained in layers of peptidoglycan

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differential stains

react differently with different kinds of microorganism eg gram stain, gram+ purple, gram - pink

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four steps of gram staining

  1. apply basic dye eg crystal violet to stain gram + bacteria

  2. apply mordant- iodine

  3. decolourize with 95% ethanol to destain gram - bacteria

  4. apply counterstain of safranin to stain decolourized cells pink

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35

why does gram + bacteria retain crystal violet stain

the thick peptidoglycan layer retains the primary stain

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36

capsule stain

india ink

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flagella staining

leifson stain

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phase contrast mircroscopy

improves contrast of unstained life cells phase ring- amplifies contrast between RI of cell and surroundings

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dark field microscopy

used to observe flagella light enters from the side, does not go through the slide

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fluorescence microscopy

cells glow on black background due to filter naturally fluorescent or dyed cells

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electron microscopy

uses electrons instead of light, the shorter wavelength of electrons gives greater resolution

  • operates in vacuum produces electron micrograph

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TEM

transmission electron microscope -cut bacterium into slices to view internal structure of the cell -0.2nm resolving power

  • specimen stained with high atomic weight substances that scatter electrons and improve contrast

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SEM

-specimen coated with thin film of heavy metal -only visualises surface scattered electrons collected + projected to produce an image

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aseptic technique

A procedure performed under sterile conditions (no living organisms)

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enrichment culture technique

isolates microbes having particular metabolic characteristics from nature

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Louis pasteur

disproved spontaneous generation theory (that life arose spontaneously from non living material)

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Koch's Postulates

  1. Pathogen must be present in all disease cases

  2. Isolate pathogen, cultivate in pure culture

  3. Inoculate into susceptible animal, initiate disease symptoms 4) Re-isolate pathogen, confirm it's the same pathogen

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Sergei Winogradsky

demonstrated that specific bacteria are linked to specific biogeochemical transformations proposed chemolithotrophy

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Martinus Beijerinck

enrichment culture technique

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Carl Woese

rRNA sequences could be used to infer evolutionary relationships (aligned sequences)

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Chemolithotrophy

oxidation of only inorganic compounds to yield energy

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the cell envelope

layered structures surrounding cytoplasm

  • cell wall -cytoplasmic membrane

  • outer membrane

  • s layers

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plasma membrane

surrounds cytoplasm

  • selective permeability; prevents influx of ions and loss of nutrients

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bacterial and eukaryotic cytoplasmic membrane

phospholipid bilayer with embedded proteins

  • fatty acid tails ; hydrophobic

  • glycerol+ phosphate+ other functional group (sugar; ethanolamine, choline) ester linkages in phospholipids

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membrane proteins

embedded- integral transmembrane- extend completely across peripheral- loosely attached/associated with membrane

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archael cytoplasmic membrane

ether linkages in phospholipids isoprenes instead of fatty acids for hydrophobic tails

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function of cytoplasmic membrane

permeability barrier (polar and charged molecules must be transported ) protein anchor energy conservation (proton motor force to drive flagella etc)

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eukaryotic plasma membrane

carbohydrates- attachment and receptor sites glycoproteins (proteins attached to carbs) sterols- role in membrane fluidity humans- cholesterol fungi- ergosterol

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active trasport

simple (driven by energy in proton motor force group translocation (binding proteins and energy from ATP) ABC system (chemical modifications of the substance driven by PEP- phosphoenolpyruvate)

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simple transport

symport- solute and H+ cotransported in one direction antiport- solute and H+ transported in opposite direction

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group translocation

substance chemically modified eg glucose phosphorylated eg phosphotransferase in E.coli -glucose, fructose, mannose (not as specific as ABC)

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ABC transporter system

ATP binding cassette substrate binding proteins have high substrate affinity

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What organisms prefer ABC transporters

extremophiles- as the transporters are very specific, efficient at finding required substances

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64

The cell wall

withstands osmotic and turgor pressure to prevent lysis maintains shape and rigidity

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gram positive and gram negative bacteria

gram positive - thick cell wall make of peptidoglycan and NO outer membrane, purple color gram-negative - thin cell wall made up of peptidoglycan WITH outer membrane, red-pink color

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Bacterial Cell wall

glycan tetrapeptide contains : -sugar backbone (NAG and NAM joined by B-1,4 linkages)

  • peptide attached to NAM

  • amino acids, L-alanine, D-alanine, L-Lysine, D-glutamic acid, DAP

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Acid fast cell walls

eg TB causing bacteria

  • high % mycolic acid (waxy lipid)

  • layer outside thin peptidoglycan layer -cells stick together and stick to surfaces

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Archael Cell walls

no peptidoglycan, no outer membrane, S layer protein shell

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pseudomurein cell wall

  • archaea similar to peptidoglycan -NAG and NAT -B1,3 linkages (lysozyme can't hydrolyse) all AAs are L stereoisomers no D

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Eukaryotic cell walls

Plants- cellulose Fungi (Chitin) -NAG units -arthropod exoskeleton Yeast cells- Glucan and Mannan

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Gram - outer membrane

second lipid bilayer external to cell wall

  • Lipopolysaccharide layer

  • surface recognition, virulence factors, strength

  • porins (transmembrane transport proteins)

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Lipopolysaccharides

-ionic bonds to divalent cations (MG, Ca) -Lipid A: endotoxin, when cell dies it is responsible for fever shock and thrombosis

  • core polysaccharide: structural stability -O polysaccharide: extends outwards; function as an antigen

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S layer

paracrystalline structure of protein/glycoprotein

  • outermost layer -strength, lysis protection, creates periplasmic space, cell surface interactions, protect cell from host defenses some archaea without a cell wall depend on s layer for strength.

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Glycolax layer( capsule/ slime layer)

polysaccharide coat outside cell envelope capsule- visible with india ink, tight matrix, tightly attached slime- loosely attached and easily deformed

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function of slime and capsule

-attachment to surfaces -maintenance of biofilms -infectivity -prevent dessication -macrophage resistant

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fimbrae and pili

composed of pillin -fimbriae: can number in 100s; stick to each other and surfaces -pili: longer than fimbriae, few per cell motility and horizontal DNA transfer

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Hamus/Hami

archaeal grappling hooks, surface attachment and biofilms

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Carbon storage polymers

PHB and PHA synthesized when C in excess glycogen

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polyphosphate granules

inorganic phosphate elemental sulfur accumulates in periplasmic granules

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magnetosomes

magnetotaxis- migration along magnetic field lines biomineralized magnetic iron oxides

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gas vesicles

confer buoyancy (floating bacteria; remain at surface for sun+oxygen) conical shaped gas filled structures

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Enospores

usually gram + dormant, tough, non-reproductive formation triggered by lack of nutrients not metabolically active UV, heat, chemical pasteurisation resistant

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Exosporium

interacts with environment/host contains spore antigens that may trigger immune response triggers germination in favourable environments

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spore coat

resistant to toxic molecules contains enzymes needed for germination

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cortex

peptidoglycan- temp resistance

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core well

UV and harsh chemical resistance

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core

chromosomal DNA encased in SASPs protect DNA from UV and heat DPA stabilises the proteins and DNA ribosomes and other structures

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Mechanisms to destroy endospores

-burning/autoclaving -ionising radiation -10% sodium hypochlorite -ethylene oxide (hospital)

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89

flagella

15-20 nm wide polar, tufts, lophotrichous, amphitrichous etc filament (flagellin) hook Basal body (motor) gram - : 2 sets of rings gram + : inner set of rings (no outer membrane so don't require additional rings to attach to membrane)

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cell movement

Clockwise - tumbles counterclockwise- runs

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Archaella

smaller than flagella rotation driven by ATP hydrolysis proteins unrelated to flagella

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surface motility

millions of cells spread over surface to colonise new area twitching and gliding motility (pili)

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twitching motility

type IV pili extend from one cell pole, attach to surface, retract to pull forward ATP hydrolysis

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gliding motility

smooth, continuous motion along long axis without external structures only bacteria helical protein track, corkscrew movement

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taxis

Movement toward or away from a stimulus.

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phototaxis

phototrophic organisms optimise position for receiving light scotophobotaxis: entering darkness causes cells to tumble and head back to light algae, cyanobacteria

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magnetotacic bacteria

use magnetic fields to remain upright to swim towards or away from O2 saves time display aerotaxis

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Cytoskeleton (eukaryotes)

microtubules, microfilaments, intermediate filaments

move proteins and chemicals/compounds to the correct area speed up movement around cell highly conserved gene sequence

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eukaryotic flagella and cilia

whiplike motion do not rotate dynein protein cilia are short flagella that beat in synchrony

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macronutrients

-carbon -oxygen -hydrogen -nitrogen -sulphur -phosphorous 96% dry weight of the cell

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