Lecture 2 Microscopy Cell Morphology Flashcards
What are the two types of cells?
Prokaryotic, eukaryotic
What is an example of prokaryotic cells?
Bacteria
archaea
What is an example of eukaryotic cells?
Eukarya
Which cell is larger?
Eukaryotic
Which cell is smaller?
Prokaryotic
What is eukaryotic cells defined by?
Presence of a nucleus
What is light microscopes magnification?
1,000x
What is electron microscopes magnification?
more than 100,000x
Scanning probe microscope can produce images of what?
Individual atoms on a surface
What are the three concepts of a bright field microscope?
Magnification, resolution, contrast
What is resolution?
Ability to distinguish two objects that are very close together
What are the two lens types in a compound microscope?
Objective and ocular
What are the magnifications of objective lenses?
4x, 10x, 40x, 100x
What is the magnification of the ocular lens?
10x
What does the condenser lens do?
focuses light on specimen
Which lens does not magnify?
Condenser lens
What is maximum resolving power of the light microscope?
0.2 micrometers
What is the point of the immersion oil on the 100x objective?
Prevents refraction of light, keeps rays from missing openings in objective lens
What do stains do in contrast?
They increase contrast but kill microbes
Electron microscopes use _______ lenses
_______
and _______ screen to replace glass lenses
Electromagnetic lenses
electrons
fluorescent
Resolving power of electron microscope
1,000 or greater
TOTAL power = 100,000x
In an electron microscope, lenses and specimen must be in _______
vacuum
Two types of electron microscopes
Transmission Electron Microscope TEM
Scanning Electron Microscope SEM
TEM is beam of electrons that pass ________ specimen or scatters
Through
TEM depends on the ________ of the region
________ is used to view internal details
density
thin-sectioning
what microscopy is a newer method that reduces damage to cells and creates 3-D images
Cry-electron microscopy
SEM is beam of electrons that scans ________ of specimen
Surface
in SEM, electrons are ________ from specimen
Released
What is a drop of liquid specimen that is overlaid with a coverslip?
Wet mount
What is simple staining?
uses a single dye to stain specimen
in a simple stain, what carries the positive charge? what carries the negative charge?
Basic dyes
acidic dyes
What are methylene blue and crystal violet?
basic dyes
An acidic dye can be done as a ________ ________
wet mount
What is differential staining
used to distinguish different groups of bacteria
What do gram positive and negative distinguish?
difference in cell wall structure
Steps of gram staining
- crystal violet (primary stain)
- iodine (mordant)
- alcohol (decolonizers)
- Safranin (counterstain)
In what step will gram + cells remain purple and gram - cells become colorless?
step 3 (alcohol)
What happens to cells in step 3 of gram stian?
gram positive: purple
Gram negative: clear
What happens in step 4 of gram stain?
gram positive: purple
gram negative: turns pink
What does the success of a gram stain depend on?
The length of time of the decolorizing step (step 3) and the age of culture
What is the acid fast stain?
used to detect organisms that do NOT readily take up dyes
What does acid fast stain detect?
Mycobacterium species such as causative agents of tuberculosis and Hansen’s disease (leprosy)
What do the cell walls of mycobacterium contain?
High concentrations of mycolic acids
Procedure of the acid fast stain
- Primary stain is concentrated red dye
- Acid fast cells retain red dye after being flooded with acid alcohol
- Methylene blue used as COUNTERSTAIN
What is the capsule stain?
Allows observation of gel-like layer that surrounds some microbes
What is stained in capsule staining?
The background
What is added to the wet mount in capsule stain?
India ink
What is endospore stain?
Allows visualization of endospores, resistant dormant cells often formed by Bacillus and Clostridium
What do endospores resist?
Gram stain, appears as clear object
Endospores stain use what to facilitate the uptake of the primary dye
Heat
What is the primary stain of endospore stain
Malachite green
What does the counterstain color in endospore stain?
Colors other cells pink that aren’t endospores
What is the counterstain of endospore stain?
Safranin
What is the flagella stain?
uses a substance that makes the dye adhere to thin flagella, making them visible
What is peritrichous cell?
Flagella surrounds the cell
What is polar cell?
Flagellum on one end
immunofluorescence uses what to tag a unique microbe protein?
Fluorescent dye-antibody labels
What shape is coccus
Spherical
What shape is rod?
Cyclindrical
Rod is also called
Bacillus
What is short rods called
Coccobacillus
Where is great diversity found?
in low nutrient environments
list other shapes from least curly to most curly
Vibrio (bent shape)
Spirillum (3 curls)
Spirochete (very curly)
Most prokaryotes divide by
Binary fission
What shape is staphylococcus
Grape like clusters
What shape is sarcina
Cubical packets
What shape is streptococcus
Chains
What shape is Neisseria gonorrhoeae
Diplococci
What layers are in the cell wall of the prokaryotic cell?
cytoplasmic membrane, cell wall, capsule (if present)
Where is chromosome located in a prokaryotic cell?
Nucleoid
What are the things on the surface of the prokaryotic cell that help with motoin?
pilus
What defines the boundary of a prokaryotic cell?
Cytoplasmic membrane
What layer is embedded with proteins?
Phospholipid bilayer
What tails face in?
Hydrophobic tails
What tails face out?
Hydrophilic tails
What are the functions of proteins?
Selective gates, sensors of environmental conditions, enzymes
What is the fluid mosaic model?
Proteins drift about in lipid bilayer
The cytoplasmic membrane is how permeable?
Selectively permeable
What passes through the cytoplasmic membrane?
O2, CO2, N2, water, small HYDROPHOBIC molecules
Some cells facilitate water passage with ________
Aquaporins
How do other molecules that can’t permeate the membrane move?
Transport systems
What does not pass through the membrane?
Sugars, ions, amino acids, ATP, macromolecules
What is simple diffusion?
Movement from high to low concentrations until equilibrium is each
What does the speed of diffusion depend on?
concentration
The greater the difference in concentration on either side of a membrane, what happens to the rate of the diffusion?
It’s higher, increases
What is osmosis?
the diffusion of water across a selectively permeable membrane due to UNEQUAL solute concentrations
Water diffuses from what areas to what areas?
high water (low solute) concentration to low water (high solute) concentration
Water flows from what solution to what solution?
hypotonic to hypertonic
There is no net water flow between what soluteions?
isotonic
Environment of prokaryotes are typically ________
Dilute/hypotonic
Water flows into the cell where the cytoplasm is a ________ solution
Concentrated/hypertonic
What prevents the cell from bursting during osmosis?
Cell wall
The electron transport chain is embedded in what?
Cytoplasmic membrane
The ETC uses energy from ________ to move ________ out of cell
Electrons, protons
ETC creates ________ gradient across membrane
Electromechanical
Energy in ETC is called
Proton motive force
Proton motive force is harvested to drive ________ and some forms of transport/motilify
ATP synthesis
Most molecules must pass through proteins functioning as ________
Selective gates
Transport systems have
Permeases or carriers
What system is highly specific?
Transport system
What is the cell wall like in a prokaryotic cell?
strong, somewhat rigid, prevents cell from bursting
Cell wall distinguishes what two types of bacteria?
Gram positive, gram negative
What is ONLY found in bacteria?
Peptidoglycan
What is peptidoglycan shaped like?
alternating series of subunits form glycan chains
What are the subunits in glycan chains
N-acetylmuramic acid (NAM)
N-acyetylglucosamine (NAG)
What are the chains that link glycan chains?
Tetrapeptide chains
What are tetrapeptide chains?
peptide interbridge in gram POSITIVE cells
Tetrapeptide only in gram….
Positive
The gram positive cell has a thick ________ layer
Peptidoglycan
What extends above peptidoglycan layer?
teichoic acids
What material is BELOW the peptidoglycan layer?
Gel-like
What is the gram negative cell wall have?
Thin peptidoglycan layer
Outside the peptidoglycan layer of the gram negative cell is a
unique outer membrane
What is the unique outer layer membrane of a gram negative cell made of
Lipopolysaccharide (LPS)
What is the function of LPS
Signals immune system of invasion by gram neg cell
- small levels elicit response to eliminate invader
What is LPS also called?
Endotoxin
What happens when large amounts of endotoxin are accumulating in the blood stream?
Can be deadly
What does LPS include?
Lipid A and O antigen
Lipid A
Recognized by immune system
O antigen
Can be used to identify species or strains
Outer membrane of gram neg cell blocks passage of many molecules like
Antibicrobial medications
Small molecules and ions can cross the outer membrane via
Porins
What is between cytoplasmic membrane and outer membrane?
Periplasmic space
What periplasmic space filled with?
gel-like periplasm
What happens in the periplasmic space?
Exported proteins accumulate unless specifically moved across outer membrane
What part of cell does crystal violet stain?
inside of cell
Gram ? cell wall prevents crystal violet-iodine complex from being washed out
positive
What dehydrates the thick layer of peptidoglycan
Decolorizing agent
What does the decolorizing agent do to the gram neg cell wall?
Damages outer membrane of the cell wall, because thin layer of peptidoglycan can’t retain dye complex
What bacteria lacks a cell wall?
Mycoplasma
What is different about mycoplasma?
It is unaffected by penicillin and lysozyme
cytoplasmic membrane contains sterols that increase strength
What is the cell walls of archaea like?
- No peptidoglycan, pseudopeptidoglycan instead
- S-layers that self assemble; built from sheets of flat protein or glycoprotein subunits
What is the description of the capsule?
distinct, gelatinous
What is the description of slime layer?
Diffuse, irregular
Most composed of glycolyx
sugar shell but some are polypeptides
Once attached to a surface, cells can grow as _______
biofilm
What is a biofilm?
Polymer encased community like dental plaque
Some capsules allow bacteria to evade ______-
Host immune system
What involves motility?
Flagella
What is an important disease related to flagella?
helicobacter pylori
What are the three parts of the bacterial flagellum
Basal body
Hook
Filament
What is different about archael flagella?
Chemically distinct, use energy from ATP instead of proton motive force
What is chemotaxis?
Bacteria sense a chemical and move toward it if its a toxin
Movement is a series of what two movements due to coordinated rotation of flagella?
Runs: straight lights
Tumbles: changes in direction
Which is longer, pili or flagella?
Flagella
Pili that allow surface attachment are called
Fimbriae
What movements involve pili?
Twitching motility, gliding motility
What do sex pilus do?
joins bacteria for DNA transfer
What is endospores?
unique type of DORMANT cell
What is endospores produced by
Bacillus, Clostridium
What is endospores resistant?
Heat, desiccation, chemicals, UV light, boiling water
Endospores can _______ to become _______ cells that can multiply
Germinate, vegetative cells
_______ is triggered by limited or nitrogen in endospores
Sporulation
What do endospore layers do?
Prevent damage
What protects the core of an endospore in dehydrates state and protects from heat?
Cortex
what plays an important protective role in endospores sporulation?
Calcium dipicolinate
_______ is triggered by heat, chemical exposure
Germination
Is germination and sporulation a means of reproduction?
No
