Exam 1 Lecture Prep

What are the 7 characteristics of life?

-Homeostasis
-Organization
-Metabolism*
-Growth
-Adaptation
-Response to stimuli
-Reproduction*

If something is alive, then it must _

-be made of one or more cells
-have a cell membrane
-have a double stranded DNA genome
-be prokaryotic or Eukaryotic

Why are viruses not considered living?

They lack a cell membrane, have varying genomes, either double or single stranded, can have RNA or DNA.

Which characteristics of life do viruses poses?

Adaptation and reproduction

Why can RNA based viruses reproduce faster?

They lack the proofreading protections that DNA reproduction has.

Why are prions not considered living?

They lack a cell membrane, Genome, and are ODD--

what is a plasmid?

a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are much used in the laboratory manipulation of genes.

When was the LUCA?

3.9 billion years ago

What are the 3 domains of life?

Bacteria, Archaea, Eukarya

Who created the microscope?

Zacharias Janssen

Who was the first person to observe and describe microorganisms accurately?

Antonie Van Leeuwenhoek

Who is the father of microbiology?

Anton van Leeuwenhoek

Describe Cell theory

1. All living organisms are composed of one or more cells
2. Cells are the basic functional units of all living organisms
3. All cells arise from preexisting cells (biogenesis)
4.

what is the Miasma theory

Diseases are caused by bad air.

what was the theory of spontaneous generation?

Abiogenesis, living organisms can arise spontaneously from non-lving material, eg frogs from mud and maggots from meat.

What did Francesco Redi do?

He had 2 jars both which contained meat. One was covered and the other was uncovered. the uncovered jar had maggots while the covered jar had none.

what did Agostini Bassi do?

showed that a disease of silkworms was caused by a fungus

Germ Theory of Disease

idea that infectious diseases are caused by microorganisms

Describe the Swan neck experiment

-An experiment done by Louis Pasteur in which a nutrient broth is heated in a flask with a swan neck, after one year, the nutrient broth remains free of microorganisms. When the curved neck is removed, the nutrient broth begins to teem with microorganisms

What did Louis Pasteur develop?

Pasteurization- allowed preservation of wine for storage. Demonstrated alcohol fermentations and other fermentations were the result of microbial activity.
-Yeast causes fermentation, converts sugars to alcohol in the absence of air.

How did Louis Pasteur overcome the spoilage problem?

He recommended heating alcohol just enough to kill bacteria- pasteurization

Describe HTST pasteurization

milk is heated at 72 degrees Celsius for 15 seconds.

Describe UHT pasteurization

milk is treated at 140 degrees Celsius for 3 seconds then cooled quickly in a vacuum chamber.

What did John Tyndall do?

Demonstrated dust carries microorganisms, proved existence of exceptionally heat-resistant forms of bacteria.

What did Joseph Lister do?

howed microorganisms were causal agents of disease, developed a system of sterile surgery

What did Robert Koch do?

-identified the bacterium that causes tuberculosis
-Led to the discovery or development of Agar, the petri dish, nutrient broth and nutrient agar, methods for isolating microorganisms

What is agar isolated from?

Algae

What are Koch's postulates?

1.The organism should be present in all animals suffering from the disease and absent from all healthy animals
2. The organisms must be grown in pure culture outside the diseased animal- anthrax, caused by Bacillus anthracis
3. When the culture is inoculated into a healthy susceptible animal, the animal must develop the symptoms of the disease
4. The organism must be re-isolated from the experimentally infected animal and shown to be the same as the original isolate.

What is Edward Jenner known as?

the father of immunology

Who developed the first attenuated vaccine against chicken cholera in 1880?

Louis Pasteur

When did antibiotic resistant bacteria emerge?

Shortly after Alexander Fleming discovered penicillin

Magnification

makes objects look larger (not limited)

resolution

the ability to see two items as separate and distinct (limited)

Resolving power

the measure of clarity of an object

Refraction

bending of light when it changes medium, eg immersion oil

transmission

light rays pass through an object

fluorescence

the use of UV light... absorb light at one wavelength and emit light at a different wavelength almost instantaneously

Absorption

light rays are taken in by an object and absorbed

The _ the magnification, the _ the NA

higher, higher

the _ magnification, the _ light is needed

more, more

NA (numerical aperture)

AAThe light gathering ability of a lens

resolving power formula

(wavelength of light)/(2x numerical aperture)
-the shorter the wavelength, the greater the resolving power

Light microscopy

use of any kind of microscope that uses visible light to observe specimens
-Uses photons
-low magnification

What are the 5 main subtypes of light microscopy?

-Bright-field
-phase contrast
-differential interference contrast
-Dark-field
-Fluorescence

what are the 2 main types of electron microscopy?

Transmission electron (TEM)
Scanning electron (SEM)

Electron microscopy

Uses electrons scattered by objects for visualization
-high magnification capability

How is resolution affected by wavelengths?

It is limited by this, as this goes down, Frequency increases, power increases, clarity is improved.

How can you improve image quality?

Using contrast or dimensionality

What is one issue that occurs when staining a specimen?

The stain used most likely will kill the specimen

What are ways to improve light to increase contrast?

Use of :
-phase contrast
-Fluorescent
-Dark field microscopy
-differential interference
-confocal scanning laser microscopy

What is a way to improve the image via dimensionality?

microtome sections

A 2 step Gram procedure is an example of what type of staining?

Differential staining

2 step gram procedure:

1) flood the heat-fixed smear with crystal violet for 1 min
2) add iodine solution for 1 minute
3)decolorize with alcohol briefly - 20 seconds
4)counterstain with safranin for 1-2 minutes

What are three types of microscopes?

Visible light
Ultraviolet rays
electron beam

How does the magnification difference between UV rays, Visible light, and electron beam microscopes?

Visible light and UV ray microscopes have a magnification up to 2000x while electron beam has a magnification range between 5000x - 1,000,000x

How do you calculate for magnification?

Occular * Objective

How does the 2 step gram stain work?

bacteria is negatively charged, adding positively charge die allows the two to bind.

What type of gram charge does gut E.coli have?

gram -

what type of gram charge does skin E.coli have?

gram +

What are lenses?

Curved, transparent surfaces that bend light waves (refraction)

describe bright-field microscopy

-Forms its image when light is transmitted through the specimen
-specimens are visualized because of slight differences in contrast that exist between them and their surrounding
-can be used with live, unstained, and preserved, stain specimens
-most widely used

Describe dark-field microscopy

-Light reaches the specimen from the sides
-the only light reaching the lens is scattered by the specimen
-does NOT use stain
-specimen appears light on a dark background
-effective for visualizing living cells that would be distorted by drying or heat that can't be stained with usual methods
-does not allow for visualization of fine internal details of cells
-the stop blocks all light from entering the objective lens except for peripheral light

How can a bright field microscope be adapted as a dark field microscope

By the addition of a stop to the condenser

Describe phase contrast microscopy

-Used for live specimens, observes motility and response to stimuli
-Used to observe unstained/lice cells and thin specimens
-specimen is contrasted against a GRAY background
-excellent for internal cell details
-more expensive than other methods

What type of microscopy would be used to observe a light sensitive organism?

dark field microscopy

how does differential interference contrast microscopy improve depth?

A polarizer is used in the condenser, polarised light splits into 2 out of phase beams, 2 beams of polarized light that are not in phase pass through the object

how does a confocal scanning laser microscope improve depth?

The image is built in stages using the ability to precisely adjust the laser focal phase

What is Differential-interference contrast microscopy useful for?

-Allows detailed view of live, unstained specimens
-provides a colorful 3D image (includes 2 prisms that add contrasting colors to the image

What source does a fluorescence microscope use?

UV radiation

Describe fluorescence microscopy

-Ultraviolet light is used to excite electrons in molecules
* Most organisms observed in this way must first be treated with a fluorescent dye or fluorochrome.
-Forms a colored image against a black field

what is fluorescence microscopy used for?

Diagnosing infections caused by specific bacteria, protozoa, and viruses using fluorescent antibodies

How do electrons avoid refraction?

by traveling in a vacuum

How are electrons able to have increased resolving power compared to visible light waves?

They travel in wavelike patterns 1000x shorter than Vis light

Describe a transmission electron microscope (TEM)

An electron beam passes through the unstained areas of the specimen, focused by electromagnets, and reflects off stained areas
lengthy preparation process = specimen undergoes lengthy dehydration process before being embedded in resin
produces 2d, black and white images
-has up to 100,000x
-electromagnets function as lenses
-operates in a vacuum
-capable of viewing structures of cells and viruses
-REQUIRES 20-100 nm thick specimens that also must be stained

what do the dark areas of TEM image represent?

Thicker/denser parts

Describe a Scanning Electron Microscope (SEM)

electron beam bombards the surface of specimen (not through it) ad scans back and forth across it.
specimen is coated in a thin layer of gold or platinum before placing in vacuum chamber.
-Has up to 650,000x magnification
-deflected electrons are picked up by a detector
-creates extremely detailed 3-D view of all kinds of objects

Which microscopy type condenses the light source into parallel rays?

Bright-field microscopy

Which microscopy type(s) can contrast samples via staining

Bright-field microscopy and Fluroescence

Which microscopy techniques require unstained cells?

Phase contrast, Differential interference contrast, and Dark-field

What type of source does a fluorescence microscope have?

a UV radiation source

What type of image is formed by a fluorescence microscope?

a colored image against a black field

what type of image results from a DIC microscope?

-detailed views of live unstained species and a colorful three dimensional image.

What size must specimens be for phase-contrast microscopy to be effective?

Thin specimens

What size must specimens be for Dark-field microscopy to be effective?

THICK

What is phase contrast microscopy used for?

-examining live specimens and their motility in response to stimuli
-examining internal cell details

What is dark field microscopy most affective for?

visualization of living cells that would be distorted by drying or heat that can't be stained with usual methods.

Does dark field microscopy allow for visualization of fine internal details of cells?

no

Which microscopes can improve the image by improving the light?

Bright-field
Phase-contrast
Dark-field

Which microscopes improve the image by improving depth?

DIC and confocal scanning laser microscopy

In what way do the stains for TEM and SEM differ?

TEM stains are thick like resin while SEM stains are specialized to repel electrons

What is the usual size of bacteria?

1x2 micrometers

Would a small cell have a larger surface area to volume ratio?

yes

Between red and blue light, which would have a higher resolving power?

blue light because resolving power increases as wavelength decreases

As cell size increases, what happens to the surface area ration?

It decreases

Cell volume impacts what?

Chemical rxn activity, as _ increases, chemical rxn activity increases

cell surface area impacts what?

the rate of exchange

What happens to surface area as cell size increases?

surface area does not increase at the same rate or extent.

As cube size increases, the surface volume ratio __

decreased

What happens when the Surface area to volume ratio decreases?

substances cannot enter the cell fast enough
waste cannot be removed fast enough-- accumulation
the cell cannot lose heat fast enough --- overheating

What can be achieved by staining specimens?

increased visibility of specimen
accentuated morphological features
preservation