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BIMM 120 > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

How does a Bright-Field microscope work

A

Specimens are visualized because of differences in contrast (optical density) between specimen and surroundings

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2
Q

Which two sets of lenses form the image

A

The objective and ocular lens

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3
Q

What is total magnification

A

(Objective magnification) x (Ocular magnification)

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4
Q

What is the light source of a miroscope

A

At the bottom of the microscope, provides a way of illuminating your sample

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5
Q

What is the condenser of a microscope

A

Focuses the light from the light source onto the sample

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6
Q

What is the stage of a microscope

A

Used to move the sample around

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7
Q

What is the typical magnification of the eye piece?

A

10X

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8
Q

What is resolution

A

The ability to distinguish two adjacent objects as separate and distinct. It determines useful magnification limit

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9
Q

How is resolution determined

A

Resolution is determined by the wavelength of light used an numerical aperture lens

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10
Q

What is the typical limit of resolution for a light microscope

A

0.2 um

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11
Q

How big are bacterial cells on average

A

Often around 1 to 5 um

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12
Q

How big are viruses on average

A

Often 0.02 um to 0.3 um, so they are too small to be resolved in light microscopes

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13
Q

What happens when you improve contrast

A

Results in a better final image

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14
Q

How do you improve contrast

A

By staining, many bacterial cells lack pigments and are very pale

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15
Q

What do you use to stain bacterial cells

A

Dyes-inorganic compounds that bind to specific cellular materials (methylene blue, safranin, and crystal violet). Most staining procedures kill cells :(

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16
Q

How do you stain a cell

A
  1. Prepare a smear by spreading a culture on a slide, then letting it air dry
  2. Pass the slide through the flame to heat fix it
  3. Flood slide with stain, rinse and dry
  4. Look at it under a microscope
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17
Q

What are differential stains

A

Used to separate bacteria into groups (gram stain)

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18
Q

What are gram stains widely used in bacteriolology

A

Bacteria can be divided into two major groups: Gram + and Gram -. Gram + appear purple and Gram - appear red

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19
Q

What is the gram stain procedure

A
  1. Flood the heat fixed smear with crystal violet (all the cells are purple)
  2. Add iodine solution (all cells remain purple)
  3. Decolorize with alcohol (Gram + cells are purple, Gram - cells are colorless)
  4. Counterstain with safranin (Gram + cells are purple and Gram - cells are pink/red)
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20
Q

What is phase-contrast microscopy

A

It optically produces contrast, phase rings in light path amplify differences in the refractive index of cell and surroundings. Resulting image is DARK cells on a LIGHT background

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21
Q

What is the advantage of phase-contrast microscopy

A

Improves the contrast of a sample without the USE of a stain, allows the visualization of LIVE samples.

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22
Q

What is dark-field microscopy

A

The light reaches the specimen from the sides, the light reaching the lens has been scattered by the specimen, the image appears LIGHT on a DARK background. Good for observing the motility of cells

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23
Q

What is fluorescence microscopy

A

Use to visualize specimens that fluoresce (emit light of one color when illuminated with shorter wavelength) and cells that autofluorescence (chlorophyll in cyanobacteria. Can be used to see subcellular parts of a cells that are normally too small to see

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24
Q

What is a fluorescent dye used on cells

A

Cells can be stained with a fluorescent dye such as DAPI, which stains DNA. DAPI does not kill cells, can be used to visualize living cells and see where in the cell DNA is.

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25
What is differential interference contrast (DIC) microscopy
Improves contrast and produces high-quality image, uses a polarizer and prism to create two distinct beams of polarized light. Gives structures such as endospores, vacuoles, and granules a 3D appearance
26
What is atomic force microscopy (AFM)
A tiny stylus is placed close to a specimen and scanned over it's surface to measure weak repulsive forces between it and the specimen's surface. A computer generates an image based on the data from the stylus and can be used to image samples from live whole cells down to isolated proteins bound to DNA, can achieve almost atomic resolution
27
What is confocal scanning laser microscopy (CSLM)
Uses computerized microscope coupled with laser source to generate a 3D fluorescence image, computer can focus the laser on single optical layers of the specimen (top, middle, bottom). The different layers can then be compiled to produce a 3D image
28
What is electron microscopy
Uses electrons instead of light (photons) to image cells and structures
29
What are the 2 types of electron microscopy
Transmission Electron Microscopes (TEM) and Scanning Electron Microscopes (SEM)
30
What is Transmission Electron Microscopy
Electromagnets function as lenses. The system operates in a vacuum (cells must be dehydrated, fixed, and stained so killed). Has a high magnification and resolution of 0.2 nm. Allows the visualization of structures inside cells at the molecular level. Specimens must be thing and stained with heavy metals
31
What is Scanning Electron Microscopy
Specimen is coated with a thin film of heavy metal (kills cells) and an electron beam scans the object's surface. The scattered electrons are collected by a detector and an image is produced
32
What do ALL cells have in common
A cytoplasmic membrane, cytoplasm containing metabolites, enzymes, ribosomes and tRNA for translation, and a DNA genome
33
Describe a Eukaryotic cell
DNA genome enclosed in a membrane-bound complex, cells are generally larger and more complex than prokaryotes, and contain membrane-obound organelles
34
Describe a Prokaryotic cell
No membrane-enclosed organelles, no nucleus, and generally smaller than eukaryotic cells
35
In a prokaryote what is a nucleoid
Region of DNA bound with proteins in a prokaryote, there is no membrane surrounding it like a nucleus in a eukaryote
36
What are viruses
They are not cells, often just DNA (or RNA) genome associated with a protein coat. They have no metabolic activities on their own and rely completely on biosynthetic machinery of infected host cell (obligate parasites). All types of cells are infected by viruses and smallest virus is only 10 nm in diameter
37
What is a genome
A cell's full complement of genes
38
What is a chromosome
An organized structure of DNA and proteins in cells. In prokaryotes they are circular and in humans they are linear
39
What are plasmids
Prokaryotes also may have small amounts of extra-chromosomal DNA (circular) called plasmids that confer special properties (antibiotic resistance)
40
What is evolution
The process of genetic change over time that results in new varieties and species of organisms. A result of reproduction, genetics, and ecology.
41
What evolves over time
Populations evolve over time, not individual cells or organisms
42
What is phylogeny
Evolutionary (genetic) relationships between organisms. Relationships can be deduced by comparing genetic information in different specimens
43
What is useful for determining phylogeny
rRNA sequences are good for determining phylogeny because ALL organisms have rRNA
44
How can you tell if two organisms are evolutionary closely related
If there are less evolutionary differences between the organisms then they may be closer evolutionary related
45
What are the 3 distinct lineage of cells
Bacteria (prokaryotic), Archaea (prokarytic) and Eukarya (eukaryotic). Archaea and Bacteria are NOT closely related even though they are both prokaryotes, Archaea is more closely related to Eukarya than Bacteria
46
What do mitochondria and chlororplasts have in common
They contain their own genomes and ribosomes. These organelles are related to a specific lineage of Bacteria. The ancestors of mitochondria and chloroplasts took up residence in Eukarya eons ago
47
What is endosymbiosis
When the mitochondria and chloroplasts started living in Eukarya and they both benefited from one another
48
Where do Archaea tend to live
They tend to live in extreme environments
49
What are chemoorganotrophs
Humans. Obtain their energy from the oxidation of organic molecules/chemicals
50
What are aerobes
They use oxygen to obtain energy
51
What are anaerobes
They obtain energy in the absence of oxygen
52
What are chemolithotrophs
Obtain their energy from the oxidation of inorganic molecules/chemicals (litho=rock,mineral)
53
What are phtotrophs
Contain organic pigments that allow them to use light as an energy source and can perform oxygenic or anoxygenic photosynthesis
54
What is oxygenic photosynthesis
Produces oxygen as a byproduct of splitting water to obtain electrons. Electrons are needed to reduce CO2 and make organic sugars. Done by plant chloroplast and cyanobacteria
55
What is anoxygenic photosynthesis
Does not produce oxygen, electrons come from other molecules other than water (H2S). Performed by green sulfur bacteria
56
What do all cells require as a major nutrient
Carbon
57
What are Autotrophs
Use CO2 as their carbon source (carbon fixation) and are referred to as primary producers
58
What are Heterotrophs
Require one or more organic molecules for their carbon source (sugars, proteins fats) and they feed directly on autotrophs or live off products produced by autotrophs
59
What are extremophiles
Organisms that inhabit extreme environments are extremeophiles. Boiling hot springs, glaciers, extremely salty bodies of water. They can't grow in "normal" conditions because their enzymes won't be able to function
60
What is the domain of all known pathogenic prokaryotes
Bacteria
61
What makes up the largest phylum of bacteria
Proteobacteria - they are Gram - (E. Coli, Pseudomonas, and Salmonella)
62
Whats another large group of bacteria but not the largest
Gram + (Bacillus, Clostridium, and Streptomyces)
63
What are cyanobacteria relatives of
They are relatives of Gram + bacteria but have a Gram - cell wall
64
What is the Deinococcus phyla of bacteria
They are extremely resistant to radioactivity, can survive dessication, and have a DNA repair process to fix DNA
65
What is the Chlamydia phyla of bacteria
They are obligate intracellular parasites and can cause disease (STD), will only grow in associated with other organisms
66
The domain Archaea contains which 2 Phyla
Euryachaeota and Crenarchaeota
67
What are the Euryachaeota
They contain methanogens, extremehalophiles and thermoacidophiles
68
What are methanogens
Degrade organic matter anaerobically to produce methan
69
What are extremehalophiles
Require high salt concentrations for metabolism and reproduction
70
What are thermoacidophiles
Grow in moderately high temperatures and low pH (acidic) environments
71
What are the Crenarchaeota
A vast majority of them are hypderthermophiles - organisms that grow at extremely high temperatures
72
What is metagenomics
A process of isolating DNA from organisms you want, sequencing the DNA of the rRNA and comparing them to a database full of other sequences DNA
73
What are Spirochetes
They cause syphillis and lyme disease
74
What are Eukaryotic macroorganisms
Animals, plants, and fungi
75
What are Eukaryotic microorganisms
Protists (algaea and protozoa), fungi, and slime molds

BIMM 120 (17 decks)

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