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GSU / Biology / BIOL 2300 / What ability does microscope give a person's naked eye?

What ability does microscope give a person's naked eye?

What ability does microscope give a person's naked eye?


School: Georgia State University
Department: Biology
Course: Microbiology and Public Health
Professor: Fuhua lu
Term: Fall 2016
Tags: eukarya, prokaryote, and Microscope
Cost: 25
Name: Microbiology 3
Description: These notes cover the different microscopes and the structures for microbial cells
Uploaded: 09/01/2016
5 Pages 60 Views 2 Unlocks

Chapter 3: Microscopy and Cell Structure  

What ability does microscope give a person's naked eye?

∙ Microscope: device giving an ability to view the microbial  world unseen by the naked eye  

∙ Principles:

o Total magnification: ocular x objective lens

o Resolution: quality of lens/ illuminating source

 Shorter wavelength: better resolution

 Immersion oil: refractive index

∙ Act as glass: enhance resolution

o Contrast:

 Phase-contrast/ interference/ dark-field/  


∙ Light Microscope

o Bright-Field: dark image against a brighter background o Dark-Field: light scattered by the sample

What are the two types of electron microscope?

 Visible objects below resolution/ unstained  


o Fluorescence:  

 Absorb UV-light (short wavelength) and emit lower energy light (long wavelength)

 Helps to see organisms that are fluorescent or  with dye

o Differential Interference: 2 beams of lights and prisms  Image: refractive inexes and thickness

 3D Image

o Scanning Laser

 Sends through sections of an organism

 Computer constructs 3D image

∙ Thicker structures If you want to learn more check out Which changes cause evolution?

∙ Details of internal structures  

Is plasmid required for host growth?

∙ Electron Microscope

o Electromagnetic lenses/ electrons/ and fluroscent screen  Electrons have high frequency and short  If you want to learn more check out How did fossils help darwin further his work and his ideas?


∙ Great resolution

o Sample must be able to absorb electrons

 Coated with heavy metal

o 2 types: Transmission and Scanning

 TEM:  

∙ Fixed sample

∙ Very thin

∙ Stained with metal

 SEM:

∙ Observe surface detail

∙ Coated with heavy metal

o Not slice

o Only examines surface  

∙ Preparation and Staining

 Increases visibility of specimen

 Specific morphological features

o Fixation

 Preserves internal and external features

 Organisms usually are killed and then firmly  

attached  Don't forget about the age old question of Who is the proponent of law of definite proportions?

∙ Heat with prokaryotes; preserves  

morphology not internal

∙ Chemical with larger ; more delicate/  

protects substructure  

o Dyes  

 Chromophore groups: chemical groups with  

conjugated double bonds with ionic, covalent, and hydrophobic

∙ Acidic: (-) ion

∙ Basic: (+) ion

∙ Mordant: increases the affinity  

 Simple stain: basic dye

∙ Determine size, shape, and arrgangement

 Differential Stain: to put microbes into groups

∙ Gram stain: primary – mordant –  

decolorizing- counter stain Don't forget about the age old question of What is required to achieve homeostasis?

o Gram (+): purple Don't forget about the age old question of What does cartesian dualism propose?

o Gram (-): pink

∙ Acid-Fast: primary- heat- decolorizing


o Acid fast: heavy waxy outer area

o Non-Acid Fast: blue  

 Special: stain specific cell structures

∙ Capsule: (india ink)(nigrosin)

o Capsules appear as halos

∙ Endospore: (malachite) w/ heat

o Endospore(green)/ vegetative (pink)

∙ Flagella: mordant and carbofuchsin to build  

the diameter  

o Prokaryotes (size, shape, and arrangement)

 Cocci: spheres

∙ Diplococcic: pairs/ streptococci: chains

∙ Staphylcocci-grape-like clusters/ tetrads- 4

∙ Sacinae- cube configuration of 8

 Bacilli- rods

∙ Coccobacilli: very short; vibrous- resembles  rods

 Spirilla: rigid helices

 Spirochetes: flexible helices

 Mycelium: network of long filaments

 Pleomorphic: variable in size If you want to learn more check out What does astrobiology study?

 Multicellular Associations

∙ Biofilm

∙ Mycobacteria glide over moist surface

o Form a swarm of cells

o Release of enzymes: breakdown  


o No H2O: fruiting bodies w

Basic Shape of a Prokaryotic Cell


d Flagell

Cell a




∙ Cytoplasmic Membrane:

o Phospholipid bilayer with peripheral and integral  proteins

 Selectively permeable

 Can be destroyed by alcohols quaternary  

ammonium, polymyxins

o Fluid Mosaic Model: membrane is viscous like olive oil

 Phospholipids move laterally

o Location: for metabolic processes (ATP)

o Detection and responsive to chemicals  

∙ Cell Wall

o PTG (peptidoglyian)

 Held together by 4 amino acids- tetrapeptide chain

o Provides shape

o Protects the cell from osmoticlysis

o Contributes to pathogenicity

o PTG as a target

 Pencillin prevents cross-linking of glycan  


 Lysozyme breaks bonds of NAG/NAM

o Some have no cell wall

 Mycoplasma: sterols account for strength

o Archaea

 Most are pseudo cell walls

o Gram (-) Cell Wall:

 Outer membrane surrounds a thin (ptg) layer  Membrane is broken: washing out the color o Gram(+) Cell Wall:

 Thick layer of PTG and teichoic acids  

∙ Lipoteichoic acid link to plasma

 The cell membrane packs tighter; cell wall is  broken

∙ External Structures

o Capsules/ slime layer

 Chemical composition varies

∙ Most: polysaccharide

 Protects from most host defense

 Capsule: gelatinous layer/ slime: irregular

o Flagella:

 Motile through sensing chemicals

 Propeller like movements

o Pili

 Shorter/ thinner than flagella

 Attachment: fimbriae

 Movements/ Conjugation

∙ Internal Structures

o Chromosomes

 Nucleoid space

 Typically singular

 Circular-double stranded

o Plasmid

 Not required for host growth

 Circular extra chromosomal DNA

 Independently replicating

 Enhance survival

o Ribosome

 Protein synthesis

 Prokaryote: 70s

 Eukaryote: 80s

o Storage Granules

 Accumulation of polymers synthesized from  excess nutrients

o Gas Vesicles

 Small protein compartments

∙ Endospores

o Resting structure formed by some bacteria for  survival

 Adverse environmental conditions

o Why so resistant?

 Calcium, acid soluble, DNA binding proteins,  dehydrated core, spore coat

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