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MBIO1010 > Chapter 2 - Microbial Cell Structure and Function > Flashcards

Chapter 2 - Microbial Cell Structure and Function Flashcards

1
Q

What kind of light does a compound light microscope use?

A

Visible light

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2
Q

How does a bright-field microscope work?

A

Specimens are visualized in contrast between specimen and surroundings

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3
Q

What are the lenses a bright-field microscope uses?

A

Objective and ocular lens

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4
Q

Magnification

A

The ability to make an object larger

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5
Q

Resolution

A

The ability to distinguish two adjacent objects as separate and distinct

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6
Q

Limit of resolution for a light microscope

A

0.2 μm

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7
Q

As wavelength decreases

A

Resolution improves

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8
Q

Two points are viewed as separate objects when

A

Light passes between them

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9
Q

What are dyes?

A

Organic compounds that bind to specific cellular materials

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10
Q

Simple Staining

A

One dye used to color specimen

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11
Q

Chromophore

A

Colored portion of dye

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12
Q

Basic dye

A

Positive charged chromophore

Binds to negatively charged molecule on cell surface

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13
Q

Acidic dye

A

Negatively charged chromophore
Repelled by cell surface
Used to stain background
Negative stain

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14
Q

Example of basic dye

A

Crystal violet

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15
Q

Example of acidic dye

A

Nigrosin

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16
Q

Gram positive

A

Cells that retain a primary stain - purple

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17
Q

Gram negative

A

Cells that lose the primary stain and take color of counterstain - red or pink

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18
Q

Acid fast stain

A

Detects mycolic acid in the cell wall of the genus Mycobacterium - pink, anything else will be blue

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19
Q

Endospore stain

A

Endospores retain primary - green, cells counterstained - pink

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20
Q

Phase-contrast microscopy

A

Phase ring amplifies differences in the refractive index of cell and surroundings

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21
Q

Advantages of phase-contrast microscopy

A

Improves the contrast of sample without the use of stain

Live samples can be seen

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22
Q

Phase-contrast appearance

A

Dark cells on a light background

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23
Q

Dark field microscopy

A

Specimen is illuminated with a hollow cone, only refracted light enters the objective

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24
Q

Dark field appearance

A

Specimen is bright and background is dark

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25
Q

Advantages of dark field microscopy

A

Observe bacteria that don’t stain well

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26
Q

Fluorescence microscopy

A

Used to visualize specimens that fluoresce

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27
Q

Fluorescence microscopy appearance

A

Emit light of one color when illuminated with another color of light. Some cells fluoresce naturally

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28
Q

Chlorophyll fluoresce

A

Absorbs light at 430 nm (blue-violet)

Emits at 670 nm (red)

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29
Q

DAPI

A

Fluorescent dye that binds to DNA

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30
Q

Differential interference contrast microscopy

A

Uses a polarizer to create two distinct beams of polarized light

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31
Q

DIC microscopy appearance

A

Structures appear three-dimensional

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32
Q

DIC structures that can be seen

A

Endospores, vacuoles, and granules

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33
Q

Confocal scanning laser microscopy

A

Uses a computerized microscope coupled with a laser source to generate a three-dimensional image

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34
Q

Advantaged of CSLM

A

Can focus on a single layer
Layers can be compiled for a three-dimensional image
Resolution is 0.1 μm

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35
Q

Wavelength of electrons

A

Much shorter than light (better resolution)

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36
Q

Transmission electron microscope

A

Electron beam focused on specimen by condenser. Electrons pass through the specimen are focused by two sets of lenses. Electrons strike a fluorescent viewing screen.

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37
Q

What is used for a lens on a TEM?

A

Magnet

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38
Q

Advantages of TEM

A

High magnification and resolution (0.2 nm)

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39
Q

Specimen requirements for TEM

A

Must be very thin (20-60 nm)

Must be stained with metal - lead or uranium

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40
Q

Why must a cell be stained with a metal?

A

To make them more electron dense

Enables visualization of structures at molecular level

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41
Q

Scanning electron microscopy

A

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.

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42
Q

SEM image

A

3D image of a specimen’s surface

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43
Q

Bacteria

A

Diverse metabolism
Live in a broad range of ecosystems
Pathogens and non-pathogens

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44
Q

Archaea

A

Diverse metabolism
Live in extreme environments
Non-pathogens

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45
Q

Coccus

A

Roughly spherical

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46
Q

Bacillus

A

Rod shaped

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47
Q

Spirillum

A

Spiral shaped

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48
Q

Spirochete

A

Spiraled and more flexible

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49
Q

Budding and appendaged bacteria

A

Have a stalk or hyphae

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50
Q

Filamentous bacteria

A

Appear like hyphae

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51
Q

Morphology does not predict

A

Physiology, ecology, phylogency

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52
Q

What shape of cells promote gliding motility?

A

Filamentous

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53
Q

What shape of cell allows swimming motility?

A

Helical or spiral-shaped

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54
Q

Advantages of small cells or those with high surface-to-volume ratio

A

Optimization for nutrient intake

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55
Q

Size range for prokaryote cells

A

0.2 μm to >700 μm

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56
Q

Size range for eukaryote cells

A

10 μm to >200 μm

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57
Q

Advantages of small cells

A

Higher surface area relative to cell volume
Support greater nutrient exchange per unit cell volume
Tend to grow faster

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58
Q

Lower limits of cell size

A
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59
Q

Small cells are found in

A

Open oceans

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60
Q

Cytoplasmic membrane

A

Thin structure that surround the cell, it separates the cytoplasm from the environment
Highly selective permeable barrier
Enables concentration of specific metabolites and excretion of waste products

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61
Q

General structure of membranes

A

Phospholipid bilayer

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62
Q

Phospholipid bilayer

A

Hydrophobic (fatty acids) and hydrophobic (glycerol-phosphate) components

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63
Q

Location of fatty acids and hydrophilic portions

A

Fatty acids point inward to form hydrophobic environment; hydrophilic portion remains exposed to external environment

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64
Q

Ester phospholipids

A

Glycerol, 2 fatty acids, phosphate, and optional side chain

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65
Q

Amphipathic

A

Has both polar and non-polar characteristics

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66
Q

Polar

A

Molecule carries a charge

Hydrophilic

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67
Q

Non-polar

A

Molecule is uncharged

Hydrophobic

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68
Q

Gram negative membrane proteins

A

Interacts with a variety of proteins (periplasmic proteins) that bind substrates or process large molecules for transport

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69
Q

Inner surface of cytoplasmic membrane

A

Interacts with proteins involved in energy-yielding reactions and other cellular functions

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70
Q

Integral membrane proteins

A

Firmly embedded in the membrane

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71
Q

Peripheral membrane proteins

A

One portion anchored in the membrane

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72
Q

Archaeal membrane linkages

A

Ether linkages in phospholipids

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73
Q

Bacterial and Eukarya membrane linkages

A

Ester linkages

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74
Q

Archaeal lipids lack and have what instead

A

Fatty acids; have isoprenes

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75
Q

Archaeal major lipids

A

Glycerol diethers and triethers

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76
Q

Structure of archaeal lipid

A

Monolayers, bilayers, or mixture

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77
Q

Advantage of monolayer lipid

A

Extremely heat resistant

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78
Q

Where are monolayer lipids usually found?

A

Hyperthermophilic archaea

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79
Q

Permeability barrier

A

Polar and charged molecules must be transported

Transport proteins accumulate solutes against the concentration gradient

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80
Q

Protein anchor

A

Holds transport proteins in place

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81
Q

Energy conservation

A

Site of generation of proton motive force

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82
Q

Carrier-mediated transport systems

A

Show saturation effect

Highly specific

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83
Q

Three major classes of transport systems in prokaryotes

A

Simple transport
Group translocation
ABC system

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84
Q

Simple transport

A

Driven by the energy in the proton motive force

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85
Q

Group translocation

A

Chemical modification of the transported substance driven by PEP (phosphoenolpyruvate)

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86
Q

What does all transport systems require?

A

Energy in some form, usually proton motive force or ATP

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87
Q

ABC system

A

Chaperone protein is used to lead the protein to the port (periplasmic binding)

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88
Q

Three transport events

A

Uniport, symport, antiport

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89
Q

Uniport

A

One direction across the membrane

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90
Q

Symport

A

Co-transporters (two molecules moves across membrane in same direction)

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91
Q

Antiporters

A

One molecule into the membrane, one molecule out

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92
Q

Example of simple transport

A

Lac permease of E. coli

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93
Q

Lac permease

A

Helps transport lactose and H+ into E. coli

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94
Q

Group translocation

A

Sugar is phosphorylated during transport across the membrane
Moves glucose, fructose, mannose
Phosphoenolpyruvate (PEP) donates a P to a phosphorelay system
P is transferred through a series of carrier proteins and deposited onto the sugar as it is brought into the cell

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95
Q

ABC transport systems

A

Involved in uptake of organic compounds (sugars, amino acids), inorganic nutrients (sulfate, phosphate), and trace metals

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96
Q

ABC transport systems display

A

High substrate specificity

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97
Q

ABC transport systems (gram-negative)

A

Employ periplasmic-binding proteins and ATP-driven transport proteins

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98
Q

ABC transport systems (gram positive)

A

Employ substrate-binding lipoproteins (anchored to external surface of cell membrane) and ATP driven transport proteins

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99
Q

ABC transports

A

Solute binding proteins, integral membrane proteins, ATP-hydrolyzing proteins

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100
Q

Solute binding protein

A

Periplasm

Binds specific substrate

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101
Q

ATP-hydrolyzing proteins

A

Supply energy for the transport event

102
Q

Cell walls of bacteria and archaea

A

Rigid - help maintain cell shape
Porous to most small molecules
Protects cell against osmotic changes

103
Q

Role of cell wall

A

Prevent cell expansion - protects against osmotic lysis
Protects against toxic substances - large hydrophobic molecules (detergents, antibiotics)
Pathogenicity
Partly responsible for cell shape

104
Q

Pathogenicity

A

Helps evade host immune system

Helps bacterium stick to surfaces

105
Q

Gram-negative cell wall

A

Two layer: LPS (lipopolysaccharide) and peptidoglycan

106
Q

Gram-positive cell wall

A

One layer: peptidoglycan

107
Q

Peptidoglycan

A

Rigid layer that provides strength to cell wall

108
Q

Polysaccharide composed of

A

N-acetylglucosamine and N-acetylmuramic acid (NAG and NAM sugars)
Amino acids
Lysine or DAP

109
Q

Polysaccharide form

A

Glycan tetrapeptide

110
Q

Number of peptidoglycan structures identified

A

More than 100

111
Q

How do peptidoglycan differ?

A

In peptide cross-links and/or interbridge

112
Q

Where are interbridges found?

A

In gram-positive bacteria, none in gram-negative

113
Q

How many interbridges does S. aureus have?

A

5 glycine residues

114
Q

How much peptidoglycan do gram-positive cell walls have?

A

Up to 90%

115
Q

What do gram positive bacteria have in their cell wall?

A

Teichoic acid

116
Q

Lipoteichoic acid

A

Teichoic acids covalently bound to membrane lipids

117
Q

Backbone of peptidoglycan

A

NAM and NAG connected by glycosidic bonds

118
Q

Glycoside bonds

A

Crosslinks formed by peptides

119
Q

Shape of peptidoglycan strand

A

Helical

120
Q

Why is the peptidoglycan strand helical?

A

Allows 3-dimensional crosslinking?

121
Q

How many layers of peptidoglycan does E. coli have?

A

1

122
Q

How many layers of cell walls does Bacillus species have?

A

50-100

123
Q

Prokaryotes that lack cell walls

A

Mycoplasmas

Thermoplasmas

124
Q

Mycoplasmas

A

Group of pathogenic bacteria

Have sterols in cytoplasmic membrane - adds strength and rigidity to membrane

125
Q

Thermoplasma

A

Species of archaea

Contain lipoglycans in membrane that have strengthening effect

126
Q

How much peptidoglycan do gram negative bacteria have?

A

10%

127
Q

What does the lipopolysaccharide layer consist of?

A

Core polysaccharide and O-polysaccharide

128
Q

What does LPS replace?

A

Most of phospholipids in outer half of outer membrane

129
Q

Endotoxin

A

Toxic component of LPS

130
Q

Periplasm

A

Space located between cytoplasmic and out membrane

131
Q

Size of periplasm

A

~15 nm wide

132
Q

Consistency of periplasm

A

Gel-like

133
Q

What does the periplasm contain?

A

Proteins

134
Q

Porins

A

Channels for movement of hydrophilic low-molecular weight substances

135
Q

Gram-positive bacteria cell walls

A

Thick consisting mainly of peptidoglycan

136
Q

What happens to gram-positive bacteria cell walls during alcohol step of staining?

A

Pores in wall close and prevent crystal violet from escaping

137
Q

What happens to gram-negative bacteria cells wall during alcohol step of staining?

A

Alcohol penetrates outer membrane, crystal violet is extracted out, and cells appear invisible until counterstained with second dye

138
Q

Archael cell walls

A

No peptidoglycan and typically no outer membrane

139
Q

Pseudomurein

A

Polysaccharide similar to peptidoglycan

140
Q

What is pseudomurein composed of

A

NAG and N-acetylalosaminuronic acid (NO NAM)

141
Q

Where is pseudomurein found?

A

Certain methanogenic archaea

142
Q

S-layers

A

Most common cell wall type among archaea

143
Q

S-layers consist of

A

Protein or glycoprotein

144
Q

S-layer structure

A

Paracrystalline structure

145
Q

True/false: some archaea only have S-layer (no other cell wall components)

A

True but most have additional cell wall elements

146
Q

Cell wall structure function in archaea

A

Prevent osmotic lysis and give shape

147
Q

Lack of peptidoglycan means archaea are resistant to

A

Lysozome and penicillin

148
Q

Cytoplasm

A

Material bounded by plasma membrane

149
Q

Protoplast

A

PM and everything within:

Macromolecules, soluble proteins, DNA and RNA, ribosomes, inclusions

150
Q

Enzymes

A

Catalyze chemical reactions

151
Q

Transport proteins

A

Move other molecules across membranes

152
Q

Structural proteins

A

Help determine shape of cell and are involved in cell division

153
Q

Proteins are made of

A

Polypeptides

154
Q

Polypeptides

A

A long polymer of amino acids joined by peptide bonds

155
Q

Nucleoid

A

Region that contains the genome

156
Q

Typical bacterial genome

A

Single circular double stranded DNA chromosome and may have one or more plasmids

157
Q

Plasmid

A

Small circular double stranded DNA that is self-replicating and carry non-essential genes

158
Q

DNA

A

Carries genetic info of all living cells

Polymer of deoxyribonucleotides

159
Q

Bacterial ribosomes

A

Site of protein synthesis

160
Q

What are the parts of the 70S ribosome?

A

30S subunit - 16S rRNA

50S subunit - 23S and 5S rRNA

161
Q

Cytoplasmic ribosomes

A

Cytoplasmic proteins

162
Q

PM associated ribosomes

A

Membrane proteins

Proteins to be exported from the cell

163
Q

Capsules and slime layers

A

Polysaccharide/protein layers that assist in attachment to surfaces

164
Q

Capsule and slime layer appearance

A

Thin or thick, rigid or flexible

165
Q

Benefits of capsule and slime layer

A

Protect against phagocytosis and resist desiccation

166
Q

Fimbriae

A

Filamentous protein structure that enable organisms to stick to surfaces or form pellicles

167
Q

Pili

A

Filamentous protein structure that assist in surface attachment

168
Q

Which is longer fimbriae or pilli

A

Pili

169
Q

What does the pili facilitate?

A

Genetic exchange between cells (conjugation)

170
Q

What type of pili are involved in twitching motility?

A

Type IV

171
Q

Cell inclusion bodies

A

Visible aggregates in cytoplasm

172
Q

Types of cell inclusion bodies

A

Carbon storage polymers: poly-beta-hydroxybutyric acid, glycogen
Polyphosphates
Sulfur globules
Magnetosomes

173
Q

What are carbon storage polymers?

A

poly-beta-hydroxybutyric acid (lipid) and glycogen (glucose polymer)

174
Q

Polyphosphates

A

Accumulations of inorganic phosphate

175
Q

Sulfur globules

A

Composed of elemental sulfur

176
Q

Magnetoaomes

A

Magnetic storage inclusions

177
Q

Inorganic inclusions

A

Polyphosphate granules and sulfur golbules

178
Q

Polyphosphate granules

A

Volutin - storage of phosphate and energy

179
Q

Sulfur globules

A

Storage of sulfur used in energy generation

180
Q

Magnetosomes

A

Intracellular granules of Fe3O4 or Fe3S4

181
Q

Magnetosomes ability

A

Gives the cell magnetic properties that allow it to orient itself in a magnetic field

182
Q

Magnetotaxis

A

Bacteria migrate along Earth’s magnetic field

183
Q

Gas vesicles

A

Confer buoyancy in planktonic cells

184
Q

Gas vesicle appearance

A

Spindle-shaped, gas-filled structures made of proteins

185
Q

Gas vesicle function

A

Decreasing cell density

186
Q

Endospores

A

Highly differentiated cells resistant to heat, harsh chemicals, and radiation

187
Q

What stage are endospores for a bacterial life cycle?

A

Dormant

188
Q

How do endospores travel?

A

Wind, water, or animal gut

189
Q

Bacterial endospores are only produced by

A

Gram positives

190
Q

Vegetative cell

A

Capable of normal growth - metabolically active

191
Q

Endospore

A

Dormant cell, formed inside of a mother cell

192
Q

Endospore: metabolically active or inactive

A

Inactive

193
Q

How are endospores triggered?

A

By lack of nutrients

194
Q

How long does it take for an endospore to form?

A

8-10 hours

195
Q

Layers of endospore

A

Spore coat and cortex and two membranes

196
Q

Spore coat and cortex

A

Protect against chemicals, enzymes, physical damage, and heat

197
Q

Two membranes of endospores

A

Permeability barriers against chemicals

198
Q

Endospore core

A

Dehydrated - protects against heat

199
Q

Endospore core is made of

A

Ca-dipicolinic acid and SASPs that protect against DNA damage

200
Q

Endospores can resist

A 
Boiling for hours
UV, gamme radiation
Chemical disinfectants
Dessication
AGe
201
Q

First stage of spore forming bacterium

A

Assymetric cell division - DNA replicates and identical chromosomes are pulled to opposites end of the cell

202
Q

Second stage of spore forming bacterium

A

Septation - divides into 2 unequal compartments: the forespore and mother cell

203
Q

Third stage of spore forming bacterium

A

Mother cell engulfs the forespore - the forespore is now surrounded by two membranes

204
Q

Fourth stage of spore forming bacterium

A

Formation of cortex - thick layers of peptidoglycan form between the two membranes

  • highly cross-linked layer - core wall
  • loosely cross-linked layer - cortex
205
Q

Fifth stage of spore forming bacterium

A

Coat synthesis - protein layers surround the core wall (spore coat and exosporium) to help protect the spore from chemicals and enzymes

206
Q

Sixth stage of spore forming bacterium

A

Endospore matures
- core is dehydrated
~ 10-30% of vegetative cell’s water content

207
Q

Seventh stage of spore forming bacterium

A

Mother cell is lysed

  • mother cell disintegrates
  • mature spore is released
208
Q

Flagella

A

Hollow protein filaments

209
Q

Flagella can be viewed

A

Only when stained

210
Q

Monotrichous

A

Single flagellum - polar or subpolar

211
Q

Amphitrichous

A

Flagella at opposite ends

212
Q

Lophotrichous

A

Multiple flagella in a single tuft

213
Q

Peritrichous

A

Flagella distributed around cell

214
Q

Flagella structure

A

Filament, hook, and basal body

215
Q

Flagella filament

A

Rigid helical protein - 20 micrometers long

Composed of identical protein subunits - flagellin

216
Q

Flagella hook

A

Flexible coupling between filament and basal body

217
Q

Basal body

A

Consist of central rod that passes through series of rings

218
Q

Basal body rings

A

L ring - LPS layer
P ring - peptidoglycan
MS ring - membrane
C ring - cytoplasm

219
Q

Where does the energy comes from to turn the flagella?

A

Proton motive force

220
Q

Proton motive force

A

Gradient of protons across the cytoplasmic membrane

  • high [H+] outside
  • low [H+} inside
221
Q

Mot proteins

A

Form a channel that allows H+ to move into the cytoplasm

Provides the energy to turn the flagellum

222
Q

How does the flagellum turn?

A

Like a propeller to drive the cell forward

223
Q

Flagellar synthesis

A

MS ring is made first, other proteins and hook are made next, filament grows from tip

224
Q

Peritrichously flagellated cell movement

A

Slowly in a straight line

225
Q

Polarly flagellated cell movement

A

Rapidly and typically spin around

226
Q

Gliding motility

A

Flagella-independent motility that is slower and smoother than swimming

227
Q

Gliding motility requires

A

Surface contact

228
Q

Mechanisms of gliding motility

A

Excretion of polysaccharide slim
Type IV pili
Gliding-specific proteins

229
Q

Taxis

A

Directed movement in response to chemical or physical gradients

230
Q

Chemotaxis

A

Response to chemicals

231
Q

Phototaxis

A

Response to light

232
Q

Aerotaxis

A

Response to oxygen

233
Q

Osmotaxis

A

Response to ionic strength

234
Q

Hydrotaxis

A

Response to water

235
Q

Chemotaxis is best studied in

A

E. coli

236
Q

Chemotaxis response

A

To temporal not spatial differences in chemical concentration

237
Q

Chemotaxis behaviour

A

Run and tumble behaviour

238
Q

Chemoreceptors

A

Used to sense attractants and repellants - biased random walk

239
Q

What happens if E. coli senses that glucose is increasing?

A

Tumble is delayed and the run lasts longer

240
Q

Chemotaxis is measured by

A

Inserting a capillary tube containing an attractant or a repellent in a medium motile bacteria
It can be seen under a microscope

241
Q

Eukaryotic cell size

A

Lower surface area to volume ratio

  • Need more sophisticated transport mechanisms
  • Grow slower
242
Q

Eukaryote nucleus

A

True nucleus that houses the genetic material

243
Q

Eukaryote internal structures

A

Membrane bound organelles
Intracytoplasmic membranes used for transport
Cytoskeleton

244
Q

Nucleus DNA

A

Multiple linear dsDNA chromosomes

245
Q

Chloroplasts

A

Site of photosynthesis for chlorophyll

246
Q

How many membranes is the chloroplast surrounded by?

A

2 membranes

247
Q

Mitochondria

A

Site of respiration and oxidative phosphorylation

248
Q

Endosymbiotic hypothesis

A

Mitochondria and chloroplasts evolved from bacteria

249
Q

What is the evidence for the endosymbiotic hypothesis?

A 
Semi-autonomous
Circular chromosomes - lack histones
70S ribosomes
Two membranes
Outer membrane has porins
250
Q

Mitochondria are most related to

A

Rickettsia - proteobacteria (obligate intracellular pathogens)

251
Q

Chloroplasts are most closely related to

A

Cyanobacteria - blue-green algae

MBIO1010 (13 decks)

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