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Microbiology 1010 > Lecture 2- Cell Structure and Function > Flashcards

Lecture 2- Cell Structure and Function Flashcards

1
Q

how does the compound light microscope work?

A

uses visible light to illuminate

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2
Q

what are the 4 different types of light microscopy?

A

bright- field
phase- contrast
dark- field
fluorescence

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3
Q

how do specimens get visualized/ seen using a bright- field microscope?

A

visualized because of differences in contract between specimen and surroundings

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4
Q

the bright- field microscope uses 2 lenses, what are they?

A

objective lens
ocular lens

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5
Q

what is the maximum magnification of a bright- field microscope?

A

~2,000x

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6
Q

how does the bright- field microscope work?

A

light source passes through the specimen, then through the objective lens, then we see the image through the ocular lens

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7
Q

why might we add oil on top of our specimen?

A

oil changes the diffraction of light and allows us to see the image clearer

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8
Q

what is magnification?

A

the ability to make an object larger

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9
Q

how do you calculate total magnification?

A

objective magnification x ocular magnification = total magnification

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10
Q

what happens in magnification is increased a lot?

A

we wont necessarily have a more clear image, resolution plays a part aswell

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11
Q

what is resolution?

A

ability to distinguish two adjacent objects as separate and distinct.
ability of a lens to distinguish small objects that are close together
when you’re walking and you see something in the horizon, it takes you a while to see it, that is resolution

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12
Q

what is the limit of resolution for a light microscope?

A

0.2µm (micrometer), therefore, two points can be distinguished if they are at least 0.2µm apart

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13
Q

as wavelength decreases, what happens to resolution?

A

increases

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14
Q

what can we use to improve contrast and result with a better final image?

A

staining!!!

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15
Q

what are characteristics of dyes that we use?

A

organic compounds
bind to specific cellular materials

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16
Q

what is simple staining?

A

one dye used to color specimen

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17
Q

what is chromophore?

A

colored portion of a dye

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18
Q

what are two types of simple staining?

A

basic dye
acidic dye

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19
Q

how does basic dye work?

A

its positively charged chromophore so it binds to negatively charged molecules on cell surface

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20
Q

how does acidic dye work?

A

its negatively charged chromophore (negative stain) so its repelled by cell surface

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21
Q

what is acidic dye used for?

A

stain background
with basic due we dye the organisms purple, therefore, the background is white
with acidic dye we dye the background purple, therefore, the light shines through the organisms

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22
Q

how do you prepare samples for staining? (6)

A
  1. spread some culture in thin film over slide using a loop
  2. dry in air
  3. pass slide over flame gently to melt specimen to slide (without killing them!)
  4. flood slide with stain
  5. rinse and dry
  6. put under microscope
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23
Q

what are 3 types of differential staining?

A

the gram stain
acid fast stain
endospore stain

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24
Q

what is the goal of the gram stain?

A

separates bacteria into 2 groups based on cell wall structure

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25
what is the process of the gram stain? slide 12.
flood the heat fixed smear with crystal violet (1min) add iodine solution (1min) decolorize with alcohol (20sec) counterstain with safranin (1min)
26
what color does gram positive turn?
purple
27
what color does gram negative turn?
red or pink
28
what does the acid fast stain do?
detects mycolic acid in the cell wall of the genus mycobacterium
29
what does the mycobacterium do? in acid fast stain
retains primary stain (pink)
30
what color does the rest of the slide turn in acid fast stain?
blue (color of counterstain)
31
what occurs in the endospore stain?
endospores retain primary (green) cells counterstained (pink)
32
what does phase- contrast microscopy do?
improves the contrast of a sample without the use of a stain
33
how does phase-contrast microscopy work?
improves contrast without the use of a stain visualization of live samples
34
what do you see when you use phase- contrast microscopy?
live samples image is dark cells on a light background
35
what do you see with dark field microscopy?
specimen is illuminated with a hollow cone of light specimen appears as a bright object on a dark background
36
how does dark field microscopy work?
only refracted light enters (thats why we see what we do)
37
what is dark field- microscopy used to observe?
bacteria that dont stain well
38
what is fluorescence microscopy used to visualize?
specimens that fluoresce
39
how does differential interference contrast microscopy work?
uses a polarizer to create two distinct beams of polarized light
40
what does interference contrast microscopy do?
gives structures such as vacuoles a three- dimensional appearance
41
if structures are not visible by bright- field microscopy what is the next microscopy to try?
differential interference contrast microscopy
42
how does confocal scanning laser microscopy work?
uses a computerized microscope coupled with a laser source to generate a three- dimensional image
43
how does the three- dimensional image work with confocal scanning laser microscopy?
the computer can focus the laser on single layers of the specimen, therefore, different layers can be compiled for a three dimensional image
44
what is the resolution for confocal scanning laser microscopy?
1µm
45
what is the difference between electron microscopes and light microscopes?
electron microscopes use electrons light microscopes use photons
46
why is it better to use electrons instead of photons?
higher resolution
47
what are the two types of electron microscopes?
transmission electron microscope scanning electron microscope
48
how does the TEM work?
electron beam focused on specimen by a condenser goes through magnets as lenses electrons pass through two magnetic lenses to see the specimen electrons strike a fluorescent viewing screen (the energy of the electrons is converted to visible light, forming an image)
49
what will happen if too many electrons are used?
specimen will get destroyed and diminish (like when you light paper on fire)
50
what is the high resolution of the TEM?
0.2nm
51
how thin does the specimen need to be for the TEM?
20- 60nm
52
why does the sample need to be so thin? tem
so that electrons can pass through it and a clear image is showed
53
what does the TEM sample need to get stained with?
dense metal such as lead or uranium
54
why does the TEM sample need to be stained with a dense metal?
metal binds to cell structures to make them more electron dense and enables visualization of structures at the molecular level
55
what is the big difference between TEM and SEM?
TEM: inside structures are viewed (due to slicing) SEM: surface areas are viewed in 3D
56
how does a scanning electron microscope work?
an electron beam scans the object scattered electrons are collected by a detector and an image is produced
57
what is the specimen coated with? SEM
specimen is coated with a thin film of heavy metal (ex. gold)
58
what is cell morphology?
the different shapes we see in cells
59
what does it mean that morphology does not predict physiology, phylogeny... in prokaryotes?
your shape is just a characteristic of your species. what you look like does not mean who you are. "dont judge a book by its cover"
60
what are the selective forces involved in setting the morphology? 3
optimization for nutrient uptake swimming motility gliding motility
61
what are the 3 more common cell shapes?
coccus (spherical) bacillus (rod shaped) spirillum (spiral shaped)
62
what are the 3 unusual cell shapes?
spirochete budding & appendaged bacteria filamentous bacteria
63
what is the average diameter of a microbe?
1.0µm ex. E. coli
64
what size of a microbe would be considered very small?
0.3µm
65
what size of a microbe would be considered very large?
80 x 600µm
66
does the open ocean normally contain small or large cells?
small! 0.2 to 0.4µm
67
how small can a microbe get? what is an unlikely size?
<0.15µm
68
what are the advantages to being small?
more SA support greater nutrient exchange per unit cell volume tend to grow faster than larger cells
69
what is the cytoplasmic membrane?
thin structure that surrounds the cell and separates the cytoplasm from its environment
70
what does the cytoplasmic membrane allow to enter?
its highly selective so it only enables concentration of specific metabolites and excretion of waste products
71
do we use diffusion across the cytoplasmic membrane?
no, it takes too long so we use channels instead
72
what makes it so that the membrane structure can exist in many different chemical forms?
variation in the groups attached to the glycerol backbone
73
what does the cell membrane contain?
phospholipid bilayer membrane proteins
74
what does a phospholipid consist of?
2 fatty acids glycerol phosphate ethanolamine (R group)
75
what does it mean that phospholipids are amphipathic?
hydrophobic and hydrophilic hydrophobic: polar (tails are inward to form hydrophobic environment) hydrophilic: non- polar (heads are exposed to external environment or the cytoplasm)
76
what linkages do phospholipids contain in bacteria and eukarya?
ester linkages
77
what is a polar molecule? charge
molecule that carries full or partial charge
78
what is a non- polar molecule? charge
molecule is uncharged
79
how tall is the cell membrane?
8-10 nm
80
how is the cytoplasmic membrane stabilized?
hydrogen bonds and hydrophobic interactions Mg^2+ and Ca^2+ help stabilize membrane by forming ionic bonds with negative charges on the phospholipids
81
gram- negative bacteria interact with a variety of proteins including periplasmic proteins, what do these proteins do?
bind substrates process large molecules for transport
82
what does the inner surface of cytoplasmic membrane interact with?
proteins involved in energy- yielding reactions and other important cellular functions
83
what types of linkages do archaeal membranes have?
ether linkages in phospholipids of archaea
84
what do archaeal membranes contain?
no fatty acids, have isoprenes instead major lipids are glycerol diethers and tetraethers
85
what form is the phospholipid in, in archaeal membranes?
lipid monolayers lipid bilayers mixture of both
86
what is unique about lipid monolayers in comparison to lipid bilayers?
lipid monolayer membranes are extremely heat resistant grow best at temperatures above 80°C
87
where are lipid monolayer membranes commonly found?
in hyperthermophilic archaea (normally in real hot places like hot springs)
88
what are the 3 functions of the cytoplasmic membrane?
permeability barrier protein anchor energy conservation
89
what is the function of the permeability barrier?
polar and charged molecules (+) must be transported transport proteins accumulate solutes against the concentration gradient
90
what is the function of the protein anchor?
holds transport proteins in place
91
what is the function of energy conservation?
generation of proton motive force (moves protons out so the cell can be negative)

Microbiology 1010 (19 decks)

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