Microbial Cell Structure and Function Flashcards
1
Q
uses visible light to illuminate cells
A
Compound light microscope
2
Q
Many different types of light microscopy:
A
Bright-field
Phase-contrast
Dark-field
Fluorescence
3
Q
the ability to make an object larger
A
Magnification
4
Q
Maximum magnification is
A
~2,000✕
5
Q
the ability to distinguish two adjacent objects as separate and distinct
A
Resolution
6
Q
is determined by the wavelength of light used and numerical aperture of lens
A
Resolution
7
Q
Limit of resolution for light microscope is about
A
0.2 μm
8
Q
Specimens are visualized because of differences in
contrast (density) between specimen and surroundings
A
Bright-field scope
9
Q
improves contrast
A
Staining
10
Q
are organic compounds that bind to specific cellular materials
A
Dyes
11
Q
Examples of common stains are
A
methylene blue, safranin, and crystal violet
12
Q
separate bacteria into groups
A
Differential stains
13
Q
Bacteria can be divided into two major groups:
A
gram-positive and gram-negative
14
Q
appear purple
A
Gram-positive bacteria
15
Q
appear red after staining
A
gram-negative bacteria
16
Q
Phase-contrast microscopy was invented in ______________ by ________________________
A
1936 by Frits Zernike
17
Q
Improves the contrast of a sample without the use of a stain
A
Phase-contrast microscopy
18
Q
Phase ring amplifies differences in the refractive index of cell and surroundings
A
Phase-contrast microscopy
19
Q
Allows for the visualization of live samples
A
Phase-contrast microscopy
20
Q
Light reaches the specimen from the sides
A
Dark-field microscopy
21
Q
Light reaching the lens has been scattered by specimen
A
Dark-field microscopy
22
Q
Image appears light on a dark background
A
Dark-field microscopy
23
Q
Excellent for observing motility
A
Dark-field microscopy
24
Q
Used to visualize specimens that fluoresce
A
Fluorescence microscopy
25
Specific on staining DNA
DAPI
26
use electrons instead of photons to image cells and structures
Electron microscopes
27
Two types of electron microscopes:
Transmission electron microscopes (TEM)
Scanning electron microscopes (SEM)
28
- Electromagnets function as lenses
- System operates in a vacuum
- High magnification and resolution (0.2 nm)
- Enables visualization of structures at the molecular level
- Specimen must be very thin (20–60 nm) and be stained
(osmic acid,permanganate, uranium lanthium or lead
salts)
Transmission electron microscopy (TEM)
29
- Specimen is coated with a thin film of heavy metal (e.g., gold)
- 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 15✕–100,000✕
Scanning electron microscopy (SEM)
30
cell shape
Morphology
31
Major cell morphologies
- Coccus (pl. cocci)
- Rod
- Spirillum
32
spherical or ovoid
Coccus (pl. cocci)
33
cylindrical shape
Rod
34
spiral shape
Spirillum
35
Cells with unusual shapes
Spirochetes, appendaged bacteria, and filamentous bacteria
36
Size range for prokaryotes
0.2 µm to >700 µm in diameter
37
Examples of very large prokaryotes
* Epulopiscium fishelsoni
* Thiomargarita namibiensis
38
Size range for eukaryotic cells:
10 to >200 µm in diameter
39
Thin structure that surrounds the cell
Cytoplasmic membrane
40
Vital barrier that separates cytoplasm from environment
Cytoplasmic membrane
41
Highly selective permeable barrier; enables concentration of specific metabolites and excretion of waste products
Cytoplasmic membrane
42
Firmly embedded in the membrane
Integral membrane proteins
43
One portion anchored in the membrane
Peripheral membrane proteins
44
Ether linkages in phospholipids of Archaea
Archaeal membranes
45
Major lipids are
glycerol diethers and tetraethers
46
Holds transport proteins in place
Protein anchor
47
Generation of proton motive force
Energy conservation
48
What are used for magnification?
Objective lens and ocular lens
49
Total magnification =
objective magnification ✕ ocular magnification
50
Differential stains:
the Gram stain
51
Resulting image is dark cells on a light background
Phase-contrast microscopy
52
Dark-field microscopy is excellent for observing __________________
motility
53
Emit light of one color when illuminated with another color
of light
fluoresce
54
Cells fluoresce naturally..example
Chlorophyll
55
Widely used in microbial ecology for enumerating
bacteria in natural samples
Fluorescence microscopy
56
Can stain both live (less efficient) and fixed cells
DAPI
57
Excited by an ultraviolet light (358nm) emit blue
color (461nm).
DAPI
58
Enables visualization of structures at the molecular level
Transmission electron microscopy (TEM)
59
Surface area:
increased 4x
60
Volume:
increased 8x
61
Composition of membranes
* General structure is ___________________________
phospholipid bilayer
62
how wide is cytoplasmic membrane
8–10 nm wide
63
Cytoplasmic membrane is stabilized by
hydrogen bonds and hydrophobic interactions
64
help stabilize membrane by forming ionic
bonds with negative charges on the phospholipids
Mg2+ and Ca2+
65
Ether linkages in phospholipids of Archaea
Archaeal membranes
66
Bacteria and Eukarya that have ester linkages in
phospholipids
Archaeal membranes
67
Archaeal lipids lack ________________; have ________________ instead
fatty acids; isoprenes
68
contains 4 5 carbon cyclopentyl and 1 6 carbon cylohexyl
Crenarcheol
69
Functions of the cytoplasmic membrane
- Permeability barrier
- Protein anchor
- Energy conservation
70
- Show saturation effect – capacity of the carrier proteins
- Highly specific – accommodate specific or closely (ex.
Amino acid) related molecules
- Highly regulated
Carrier-mediated transport systems
71
Three major classes of transport systems in prokaryotes
- Simple transport
- Group translocation
- ABC system
72
Driven by the energy in the proton motive force
Simple transport
73
Chemical modification of the transported substance driven by phosphoenolpyruvate
Group translocation
74
Periplasmic binding proteins are involved and energy comes from ATP
ABC transporter
75
Three transport events are possible:
uniport, symport, and antiport
76
transport in one direction across the membrane
uniport
77
function as co-transporters
symport
78
transport a molecule across the membrane while simultaneously transporting another molecule in the opposite direction
antiport
79
Gram-negative cell wall
Two layers:
LPS and peptidoglycan
80
Gram-positive cell wall
One layer:
peptidoglycan
81
Rigid layer that provides strength to cell wall
Peptidoglycan
82
Gram-positive cell walls can contain up to ___________ peptidoglycan
90%
83
Gram-positive cell walls are common to have ______________________ (acidic substances) embedded in their cell wall
teichoic acids
84
teichoic acids covalently bound to membrane lipids
Lipoteichoic acids
85
Prokaryotes that lack cell walls
- Mycoplasmas
- Thermoplasma
86
Group of pathogenic bacteria
Mycoplasmas
87
Species of Archaea
Thermoplasma
88
have sterols on their cell membrane
Mycoplasma
89
have lipoglycans in their cell membrane
Thermoplasma
90
Most of cell wall composed of ________________________, aka
_______________________
outer membrane; lipopolysaccharide
91
LPS consists of
core polysaccharide and O-polysaccharide
92
the toxic component of LPS
Endotoxin
93
space located between cytoplasmic and outer
membranes
Periplasm
94
Houses many proteins including those filtered by the outer
membrane
Periplasm
95
channels for movement of hydrophilic low-molecular-weight substances
Porins
96
Facilitates the entry of materials needed by the cell that by the outer membrane
Porins
97
water filled channels where small substances can pass through
Non-specific Porins
98
contain binding site for specific or structurally related
substances
Specific Porins
99
- No peptidoglycan
- Typically no outer membrane
Archaeal Cell Walls
100
Polysaccharide similar to peptidoglycan
Pseudomurein
101
Cell walls of some Archaea lack
pseudomurein
102
Found in cell walls of certain methanogenic Archaea
Pseudomurein
103
- Most common cell wall type among Archaea
- Consist of interlocking protein or glycoprotein
S-Layers
104
Allows the archea to withstand strong osmotic pressure
S-Layers
105
Serves as a filter to only allow solutes of lower molecular
weight
S-Layers
106
Resistant to lysozyme
S-Layers
107
thin sheets of cells on a liquid surface
pellicles
108
Enable organisms to stick to surfaces or form pellicles
(thin sheets of cells on a liquid surface) or biofilm
Fimbriae
109
Also enhances bacterial virulence as it assist disease
process (attachment to tissue)
Fimbriae
110
Typically longer than fimbriae
Pili
111
Facilitate genetic exchange between cells (conjugation)
Pili
112
genetic exchange between cells
conjugation
113
involved in twitching motility
Type IV pili
114
Receptor for certain viruses
Pili
115
lipid compose of 3-18 carbons
Poly-β-hydroxybutyric acid (PHB)
116
glucose polymer
Glycogen
117
accumulations of inorganic phosphate
Polyphosphates
118
composed of elemental sulfur stored in the periplasm
Sulfur globules
119
Carbonate minerals: composed of
barium, strontium, and magnesium
120
magnetic storage inclusions (iron oxide mineral magnetite Fe3O4 )
Magnetosomes
121
Allows the bacterial cells to orient themselves within a
magnetic field. Not observed in archea
Magnetosomes
122
Confer buoyancy in planktonic cells
Gas vesicles
123
Spindle-shaped, gas-filled structures made of protein
Gas vesicles
124
Gas vesicles are composed of two proteins
GvpA and GvpC
125
water tight vesicle shell
GvpA
126
strengthen the shell of the gas vesicle
GvpC
127
Highly differentiated cells resistant to heat, harsh
chemicals, and radiation
Endospores
128
- Ideal for dispersal via wind, water, or animal gut
- Present only in some gram-positive bacteria
Endospores
129
Endospore structure
- Core contains
small acid-soluble spore proteins (SASP)
130
structure that assists in swimming
Flagella
131
Different arrangements of Flagella:
- peritrichous (everywhere)
- polar (on side)
- lophotrichous (many flagella on one side)
132
everywhere
peritrichous
133
on side
polar
134
many flagella on one side
lophotrichous
135
flagella shape is
helical
136
Flagellar structure of Bacteria
- filament composed of different types of protein called
flagellin
137
Flagellar structure of Bacteria
- Move by
rotation- like a propeller
138
Flagellar structure of Archaea
- Move by
rotation
139
increase or decrease rotational speed in
relation to strength of the proton motive force
Flagella
140
move slowly in a straight line
Peritrichously flagellated cells
141
move more rapidly and typically spin around
Polarly flagellated cells
142
- Flagella-independent motility
- Slower and smoother than swimming
Gliding motility
143
- Movement typically occurs along long axis of cell
- Requires surface contact
Gliding motility
144
Mechanisms of gliding motility
- Excretion of polysaccharide slime
- Type IV pili
- Gliding-specific proteins
145
directed movement in response to chemical or physical gradients
Taxis
146
response to chemicals
Chemotaxis
147
response to light
Phototaxis
148
response to oxygen
Aerotaxis
149
response to ionic strength
Osmotaxis
150
response to water
Hydrotaxis
151
Chemotaxis is best studied on
E.coli
152
“Run and tumble” behavior
Chemotaxis
153
Chemotaxis
Attractants and receptors sensed by
chemoreceptors
154
contain a membrane-enclosed nucleus and other
organelles
Eukaryotes
155
contains the chromosomes
Nucleus
156
DNA is wound around
histones
157
Visible under light microscope without staining
Nucleus
158
Within the nucleus is the
nucleolus
159
Site of ribosomal RNA synthesis
nucleolus
160
- Normal form of nuclear division in eukaryotic cells
- Chromosomes are replicated and partitioned into two
nuclei
Mitosis
161
Mitosis results in
two diploid daughter cells
162
- Specialized form of nuclear division
- Halves the diploid number to the haploid number
Meiosis
163
Meiosis results in
four haploid gametes
164
All specialize in energy metabolism
Mitochondria, Hydrogenosomes, and Chloroplast
165
* Respiration and oxidative phosphorylation
* Bacterial dimensions (rod or spherical)
* Over 1,000 per animal cell
* Surrounded by two membranes
Mitochondria
166
Mitochondria has folded internal membranes called
cristae
167
Contain enzymes needed for respiration and ATP
production
cristae
168
Innermost area of mitochondrion called
matrix
169
Contains enzymes for the oxidation of organic compounds
matrix
170
* Similar size to mitochondria; however, lack TCA cycle
enzymes and cristae
* Oxidation of pyruvate to H2 , CO2 , and acetate
* Trichomonas and various protists have hydrogenosomes
Hydrogenosome
171
Chlorophyll-containing organelle found in phototrophic
eukaryotes
Chloroplast
172
Flattened membrane discs are
thylakoids
173
Lumen of the chloroplast is called the
stroma
174
Stroma contains large amounts of
RubisCO
175
RubisCO is key enzyme in
Calvin cycle
176
Two types of ER
smooth and rough ER
177
participates in the synthesis of lipids
Smooth ER
178
is a major producer of glycoprotein
Rough ER
179
stacks of membrane distinct from, but functioning in concert with, the ER
Golgi complex
180
Modifies products of the ER destined for secretion
Golgi complex
181
- Membrane-enclosed compartments
- Contain digestive enzymes used for hydrolysis
Lysosomes
182
Allow for lytic activity to occur within the cell without
damaging other cellular components
Lysosomes
183
25 nm in diameter; composed of α- and β-tubulin
Microtubules
184
Function in maintaining cell shape, in motility, in chromosome movement, and in movement of organelles
Microtubules
185
7 nm in diameter; polymers of actin
Microfilaments
186
Function in maintaining cell shape, motility by pseudopodia,
and cell division
Microfilaments
187
8–12 nm in diameter; keratin proteins
Intermediate filaments
188
Function in maintaining cell shape and positioning of
organelles in cell
Intermediate filaments
189
Organelles of motility allowing cells to move by swimming
Flagella and cilia
190
are short flagella
Cilia
191
is attached to the microtubules and uses ATP
Dynein
192
Flagella and cilia propel the cell using a
whiplike motion
