Ch 2 Flashcards
1
Q
___ ___ microscopes uses visible light to illuminate cells.
A
Compound light
2
Q
Many different types of light microscopy:
A
- bright-field
- phase-contrast
- dark-field
- flourescence
3
Q
Bright-field scope:
A
Specimens are visualized because of differences in contrast between specimen and surroundings
4
Q
Two sets of lenses form the image:
A
Objective lens
Ocular lens
5
Q
Total magnification=
A
Objective magnification x ocular magnification
6
Q
Magnification:
A
The ability to make an object larger
7
Q
Resolution:
A
The ability to distinguish two adjacent objects as separate and distinct
8
Q
___ is determined by the wavelength of light used and numerical aperture of lens.
A
Resolution
9
Q
Limit of resolution for light microscope is about ___.
A
2 um
10
Q
Improving ___ results in a better final image.
A
Contrast
11
Q
___ improves contrast.
A
Staining
12
Q
___ are organic compounds that bind to specific cellular materials.
A
Dyes
13
Q
Examples of common stains are:
A
- methylene blue
- safranin
- crystal violet
14
Q
Differential stains:
A
The gram stain
- separate bacteria into groups
15
Q
Bacteria can be divided into two major groups:
A
Gram-positive and gram-negative
16
Q
Gram-positive bacteria appear ___, and gram-negative bacteria appear ___ after staining.
A
Purple, red
17
Q
Phase-contrast microscopy
A
- phase ring amplifies differences in the refractive index of cell and surroundings
- improves the contrast of a sample without the use of a stain
- allows for visualization of live samples
- resulting image is dark cells on a light background
18
Q
Dark-field microscopy
A
- light reaches the specimen from the sides
- light reaching the lens has been scattered by specimen
- image appears light on a dark background
- excellent for observing motility and spirochaetes
19
Q
Fluorescence microscopy
A
- used to visualize specimens that flouresce
20
Q
Fluoresce
A
Emit light of one color when illuminated with another color of light
21
Q
Autofluorescence
A
Cells fluoresce naturally or after they have been stained with a fluorescent dye such as DAPI
22
Q
Electron microscopes uses ___ instead of ___ to image cells and structures
A
Electrons, photons
23
Q
Two types of electron microscopes:
A
Transmission electron microscope
Scanning electron microscope
24
Q
Transmission electron microscope (TEM)
A
- electromagnets function as lenses
- system operates in a vacuum
- high magnification and resolution (.2nm)
- enables visualization of structures at the molecular level
- specimen must be very thin and be stained
25
Scanning electron microscopy (SEM)
- specimen is coated with a thin film of heavy metal
- an electron beam scans the object
- scattered electrons are collected by a detector, and an image is produced
- even very large specimens can be observed
- magnification range of 15X-100,000X
26
Morphology:
Cell shape
27
Coccus
Spherical or ovoid
28
Rod
Cylindrical shape
29
Spirillum
Spiral shape
30
Size range for prokaryotes:
.2 um to 700 um in diameter
31
Size range for eukaryotic cells:
10 to 200 um in diameter
32
Cytoplasmic membrane
- thin structure that surrounds the cell
- vital barrier that separates cytoplasm from environment
- highly selective permeable barrier; enables concentration of specific metabolites and excretion of waste products
33
Composition of membranes
General structure is ___ ___
Phospholipid bilayer
34
Can exist in many different chemical forms as a result of variation in the groups attached to the ___ ___.
Glycerol backbone
35
Fatty acids point inward to form ___ ___; hydrophilic portions remain exposed to ___ ___ or the cytoplasm.
Hydrophobic environment; external environment
36
Integral membrane proteins
Firmly embedded in the membrane
37
Peripheral membrane proteins
One portion anchored in the membrane
38
___ linkages in phospholipids of archaea.
Ether
39
Bacteria and Eukarya that have ___ linkages in phospholipids.
Ester
40
Archaeal lipids lack ___ ___; have ___ instead.
Fatty acids; isoprenes
41
Permeability barrier
- polar and charged molecules must be transported
| - transport proteins accumulate solutes against the concentration gradient
42
Protein anchor
Holds transport proteins in place
43
Energy conservation
Generation of proton motive force
44
Three transport events are possible:
Uniport, symport, and antiport
45
Uniporters
Transport in one direction across the membrane
46
Symporters
Function as co-transporters
47
Antiporters
Transport a molecule across the membrane while simultaneously transporting another molecule in the opposite direction
48
Gram-negative cell wall
Two layers: LPS and peptidoglycan
49
Gram-positive cell wall
One layer: peptidoglycan
50
Peptidoglycan
Rigid layer that provides strength to cell wall
51
Polysaccharide composed of:
- N-acetylglucosamine and N-acetylmuramic acid
- amino acids
- cross-linked differently in gram-negative bacteria and gram-positive bacteria
52
Gram-positive cell walls can contain up to ___ peptidoglycan
90%
53
Teichoic acids
Acidic substances
54
Lipoteichoic acids
Teichoic acids covalently bound to membrane lipids
55
Common to have ___ ___ embedded in gram-positive cell walls
Teichoic acids
56
Prokaryotes that lack cell walls
- mycoplasmas
| - Thermoplasma
57
Mycoplasmas
Group of pathogenic bacteria
58
Thermoplasma
Species of archaea
59
Most of cell wall composed of ___ ___, aka lipopolysaccharide (LPS) layer
Outer membrane
60
LPS consists of ___ ___ and ___
Core polysaccharide and O-polysaccharide
61
Endotoxin
The toxic component of LPS
62
Periplasm
Space located between cytoplasmic and outer membrane
63
Porins
Channels for movement of hydrophilic low-molecular-weight substances
64
Capsules and slime layers
- assist in attachment to surfaces
- protect against phagocytosis
- resist desiccation
65
Fimbriae
- filamentous protein structures
| - enable organisms to stick to surfaces, form pellicles, or biofilms on solid surfaces
66
Pellicles
Thin sheets of cells on a liquid surface
67
Pili
- filamentous protein structures
- typically longer than Fimbriae
- assist in surface attachment
- facilitate genetic exchange between cells
68
Conjugation
Exchange between cells
69
Endospores
- highly differentiated cells resistant to heat, harsh chemicals, and radiation
- "dormant" stage of bacterial life cycle
- ideal for dispersal via wind, water, or animal gut
- present only in some gram-positive bacteria
70
Flagella
Structure that assists in swimming
- peritrichous, polar, lophotrichous
- helical in shape
71
Flagellar structure of bacteria
- filament composed of Flagellin
| - move by rotation
72
Peritrichously flagellated cells
Move slowly in a straight line
73
Polarly flagellated cells
Move more rapidly and typically spin around
74
Chemotaxis
Best studied in E. coli
"Run and tumble" behavior
Bacteria respond to temporal difference in chemical concentration
75
Attractants and receptors sensed by ___.
Chemoreceptors
76
Bright-field used to look at..
Dead, stained organisms
77
Phase contrast and dark field used to look at..
Living organisms
78
Basic stain/dye
+ charge
79
Acidic stain/dye
- charge
80
___ ___ will allow us to see the capsule
Negative stain
81
Simple stain
Stains cells all one color
82
Thick peptidoglycan layer
Gram +
83
Thin peptidoglycan layer
Gram -
84
Streptococcus
Chain
85
Staphylococcus
Cluster
86
Vibrio usually ..
Curve shaped rod
87
Monotrichous or polar flagellum
One single flagella
88
Lophotrichous
Few flagella on one side
89
Amphitrichous
Few flagella on opposite ends
90
Peritrichous
Flagella all around
91
Largest we will look at
Bacillus sabtilis
| Large gram - rod
92
Smallest we will look at
Streptococcus
| Gram + cocci
93
Passive transport
High -> low
| Doesn't need ATP
94
Active transport
Low -> high
| ATP is required
95
Bacillus and Claustrudium
Both gram + rods
Bacillus needs oxygen
Claustrudium hates oxygen
