ch 2 - how we see invisible world

what is visible light made of?

electromagnetic waves

what is wavelength?

distance between one peak of a wave & the next peak

what is amplitude?

height of each peak

what is frequency?

rate of vibration of wave or number of wavelengths within a specified time period

what are the different interactions of light?

• reflection - wave bounces off of a material

• transmission - wave travels through material, ex” light through glass

• refraction - light waves change direction as they enter new medium

transparency vs opaque

• transparency

  • more see through; allows large population of light to be transmitted

• opaque

  • less see through'; minimizes transmission of light

what is focal point?

image point when light entering lens is parallel

what is magnification?

defined as ability of a lens to enlarge image of object when compared to real object

what is resolution?

ability to tell that two separate points or objects are separate

what is contrast?

difference in light intensity or color between microscopic specimen & its surrounding background

what is lens?

• curved optical glass surface inside microscope

  • refracts light to magnify & focus images of tiny microorganisms like bacteria & cells

who created the first microscope (aka simple microscope)?

Antonie van Leeuwenhoek

what are light microscopes?

• uses light to visualize images

• total magnification = objective x ocular

what is a Brightfield microscope?

• most common

• produces image on bright background

what are the different types of light miscroscopy?

• dark

• phase-contrast

• fluorescence

• confocal

what is a dark light miscroscope?

• increases contrast w/o staining by producing bright mage on darker background

• good for viewing live specimen

what is a phase contrast light miscroscope?

• uses refractino & interference caused by structures in specimen to create high-contrast, high-resolutino images wo staining

• good for live specimen & structures

what is a fluorescence light microscope?

• uses fluorescent stains to produce image

• used to ID pathogens, find particular species, distinguish living from dead cells, or find locations of specific molecules within a cell

what is a confocal light microscope?

• uses laser to scan multiple z-planes successively, producing many 2D, high-resolution images of diff depths

  • can be constructed into 3D image by computer

• good for viewing thick specimens

what is a transmission electron microscope (TEM)?

• uses electron beams that pass through specimen to visualize small images

• useful to observe small, thin specimens such as tissue sections & subcellular structures

what is a scanning electron microscope (SEM)?

• uses electron beams to visualize surfaces

• useful to observe 3D surface details of specimens

what is biofilm?

complex community of 1 or more microorganism species, typically forming as a slimy coating attached to surface or at interface between surfaces

which type of microscopy would work best to visualize microbes in a biofilm?

confocal microscopy

what are wet mounts?

the specimen is placed on the slide in a drop of liquid

what is a fixation?

• process of attaching cells to a slide

• often achieved either by heating or chemically treating the specimen

• also kills microorganism in specimen

what is a basic dye?

stain classified as basic dye if chromophore (colored ion) is positively charged ion

what is an acidic dye?

stain classified if negative ion is the chromophore

positive stain

• dye that will be absorbed by cells or organisms being observed

• adds color to objects of interest to make them stand out against background

negative stain

• absorbed by background but not cells or organisms in specimen

• produces an outline or silhouette of organisms against colorful background

simple staining

• single dye used to emphasize particular structures in specimen

• generally makes all organisms in a sample appear to be same color even if it contains more than one type of organism

differential staining

• distinguishes organisms based on their interactions w multiple stains

  • 2 diff organisms may be seen w diff colors

what are some examples of the simple stains?

• basic stains

• acidic stains

• negative stains

what are some examples of differential stains?

• gram stain

• acid-fast stain

• endospore stain

• flagella stain

• capsule stain

what are some examples of gram stain?

• crystal violet

• iodine

• alcohol

• safranin