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MICROPARA [LEC] > Microbial Cell Structure and Function > Flashcards

Microbial Cell Structure and Function Flashcards

1
Q

__________ uses visible light to
illuminate cells.

A

Compound light microscope

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2
Q

Many different types of light microscopy:

A

• Bright-field
• Phase-contrast
• Dark-field
• Fluorescence

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3
Q

It is the ability to make an object larger

A

Magnification:

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4
Q

Total magnification formula

A

objective magnification + ocular magnification

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5
Q

Maximum magnification

A

2,000+

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6
Q

It is the ability to distinguish two adjacent objects as
separate and distinct

A

Resolution

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7
Q

Resolution is determined by __________ and __________.

A

wavelength of light used and
numerical aperture of lens

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8
Q

Limit of resolution for light microscope

A

0.2 μm

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9
Q

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

A

Bright-field scope

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10
Q

Improving contrast results in __________.

A

better final image

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11
Q

Staining improves __________.

A

contrast

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12
Q

__________ are organic compounds that bind to specific
cellular materials

A

Dyes

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13
Q

Examples of common stains:

A

methylene blue
safranin
crystal violet

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14
Q

Differential stains

A

Gram stain

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15
Q

Differential stains separate bacteria into __________.

A

groups

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16
Q

Bacteria can be divided into two major groups:

A

gram-positive and gram-negative

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17
Q

Gram-positive bacteria appear __________, and gram-negative bacteria appear __________ after staining.

A

Purple; red

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18
Q

• Improves the contrast of a
sample without the use of a
stain
• Allows for the visualization of
live samples
• Resulting image is dark cells
on a light background

A

Phase-contrast microscopy

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19
Q

Phase-contrast microscopy was Invented in 1936 by __________.

A

Frits Zernike

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20
Q

Phase-contrast microscopy :

__________ amplifies differences in the refractive
index of cell and surroundings

A

Phase ring

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21
Q

• 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

A

Dark-field microscopy

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22
Q

__________ used to visualize specimens that fluoresce
• Emit light of one color when illuminated with another color of light

A

Fluorescence microscopy

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23
Q

__________ use electrons instead of photons to image cells and structures

A

Electron microscopes

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24
Q

Two types of electron microscopes:

A

• Transmission electron microscopes (TEM)
• Scanning electron microscopes (SEM)

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25
Q

• 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

A

Transmission electron microscopy (TEM)

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26
Q

• 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+ to 100,000+

A

Scanning electron microscopy (SEM)

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27
Q

Morphology :

A

Cell Shape

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28
Q

Major cell morphologies

A

• Coccus (pl. cocci): spherical or ovoid
• Rod: cylindrical shape
• Spirillum: spiral shape

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29
Q

Cells with unusual shapes:

A

Spirochetes, appendaged bacteria, and filamentous
bacteria

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30
Q

Morphology typically does not predict physiology,
ecology, phylogeny, etc. of a __________.

A

prokaryotic cell

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31
Q

May be selective forces involved in setting the
morphology:

A

• Optimization for nutrient uptake (small cells and those with high surface-to-volume ratio)
• Swimming motility in viscous environments or near
surfaces (helical or spiral-shaped cells)
• Gliding motility (filamentous bacteria)

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32
Q

Size range for prokaryotes

A

0.2 µm to >700 µm in diameter

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33
Q

Most cultured rod-shaped bacteria are between:

A

0.5 and 4.0 µm wide and < 15 µm long

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34
Q

Size range for eukaryotic cells:

A

10 to >200 µm in diameter

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35
Q

Surface-to-volume ratios, growth rates, and evolution:

Advantages to being small :

A

• Small cells have more surface area relative to cell volume than large cells (i.e., higher S/V)
• Support greater nutrient exchange per unit cell
volume
• Tend to grow faster than larger cells

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36
Q

Membrane Structure:

• 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

A

Cytoplasmic membrane

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37
Q

Composition of membranes:

General structure is phospholipid bilayer

A

Contain both hydrophobic and hydrophilic components.

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38
Q

Composition of membranes:

Can exist in many different chemical forms as a result of variation in the groups attached to the __________.

A

the glycerol backbone

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39
Q

Fatty acids point inward to form ___________; __________ portions remain exposed to external environment or the cytoplasm

A

hydrophobic environment; hydrophilic

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40
Q

Cytoplasmic membrane are __________nm wide.

A

8–10 nm wide

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41
Q

Protiens firmly embedded in the membrane

A

Integral membrane proteins

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42
Q

Protein with one portion anchored in the membrane

A

Peripheral membrane proteins

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43
Q

__________ surface of cytoplasmic membrane can interact with a variety of proteins that bind substrates or process large molecules for transport.

A

Outer

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44
Q

__________ surface of cytoplasmic membrane interacts with proteins involved in energy-yielding reactions and other important cellular functions

A

Inner

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45
Q

Can exist as lipid monolayers, bilayers, or mixture

A

Archaeal membranes

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46
Q

Archaeal membranes:
Major lipids are _________ and __________.

A

glycerol diethers and tetraethers

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47
Q

A monolayer (Extremely resistant to
heat)

A

Glycerol tetraether

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48
Q

This contains 4 5 carbon cyclopentyl and 1 6
carcon cylohexyl

A

Crenarcheol

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49
Q

Permeability barrier :
Polar and charged molecules must be __________.

A

transported

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50
Q

Permeability barrier:
Water pass through the membrane freely: __________ accelerate its movement

A

Aquaporins

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51
Q

Holds transport proteins in place

A

Protein anchor

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52
Q

Generation of proton motive force

A

Energy conservation

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53
Q

• Show saturation effect – capacity of the carrier proteins
• Highly specific – accommodate specific or closely (ex.
Amino acid) related molecules
• Highly regulated

A

Carrier-mediated transport systems

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54
Q

Three major classes of transport systems in prokaryotes:

A

• Simple transport
• Group translocation
• ABC system

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55
Q

All require energy in some form, usually _________ or _________

A

proton motive force or ATP

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56
Q

Driven by the energy in the proton motive
force

A

Simple transport

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57
Q

Chemical modification of the transported substance driven by phosphoenolpyruvate

A

Group translocation

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58
Q

Periplasmic binding proteins are involved and energy comes from ATP.

A

ABC transporter

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59
Q

Nutrient Transport
Three transport events are possible

A

uniport,
symport
antiport

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60
Q

transport in one direction across the membrane

A

Uniporters

61
Q

function as co-transporters

A

Symporters

62
Q

transport a molecule across the membrane while simultaneously transporting another molecule in
the opposite direction.

A

Antiporters

63
Q

Species of Bacteria separated into two groups
based on Gram stain

A

Gram-positives and gram-negatives

64
Q

Gram-positives and gram-negatives have different
cell wall structure

A

• Gram-negative cell wall
Two layers: LPS and peptidoglycan

• Gram-positive cell wall
One layer: peptidoglycan

65
Q

• Rigid layer that provides strength to cell wall

Polysaccharide composed of:
• N-acetylglucosamine and N-acetylmuramic acid
• Amino acids
• Lysine or diaminopimelic acid (DAP)
• Cross-linked differently in gram-negative bacteria and
gram-positive bacteria (Figure 2.26)

A

Peptidoglycan

66
Q

• Can contain up to 90% peptidoglycan
• Common to have teichoic acids (acidic substances)
embedded in their cell wall
• Lipoteichoic acids: teichoic acids covalently bound to
membrane lipids
• Responsible for the negative electrical charge of the cell surface.
• Bind to Ca2+ and Mg+

A

Gram-positive cell walls

67
Q

These are teichoic acids covalently bound to membrane lipids

A

Lipoteichoic acids

68
Q

Prokaryotes that lack cell walls

A

Mycoplasmas
Thermoplasma

69
Q

Prokaryotes that lack cell walls:

Group of pathogenic bacteria

A

Mycoplasmas

70
Q

Prokaryotes that lack cell walls:

Species of Archaea

A

Thermoplasma

71
Q

Reasons of survival
1. Have tough cytoplasmic membrane
__________ – have sterols on their cell membrane
__________ – have lipoglycans in their cell membrane

  1. They live in an osmotically protected habitats
A

Mycoplasma; Thermoplasma

72
Q

Total cell wall contains ___________ % peptidoglycan

A

10%

73
Q

Most of cell wall composed of outer membrane, aka __________ layer.

A

lipopolysaccharide (LPS)

74
Q

the toxic component of lipopolysaccharide (LPS) layer

A

Endotoxin

75
Q

space located between cytoplasmic and outer
membranes

A

Periplasm

76
Q

Periplasm is ___________ wide.

A

~15 nm wide

77
Q

• Contents have gel-like consistency
• Houses many proteins including those filtered by the outer membrane.
• Hydrolytic enzymes, binding proteins, chemoreceptors

A

Periplasm

78
Q

channels for movement of hydrophilic
low-molecular-weight substances

A

Porins

79
Q

• Facilitates the entry of materials needed by the cell that by the outer membrane.
• Non-specific – water filled channels where small substances can pass through
• Specific – contain binding site for specific or structurally related substances.

A

Porins

80
Q

Structural differences between cell walls of
gram-positive and gram-negative Bacteria are
responsible for differences in the __________.

A

Gram stain reaction

81
Q

Cell Walls that has • No peptidoglycan
• Typically no outer membrane

A

Archaeal Cell Walls

82
Q

• Polysaccharide similar to peptidoglycan (Figure 2.30)
• Composed of N-acetylglucosamine and Nacetylalosaminuronic
acid
• Found in cell walls of certain methanogenic Archaea

A

Pseudomurein

83
Q

Cell walls of some Archaea lack

A

pseudomurein

84
Q

• Most common cell wall type among Archaea
• Consist of interlocking protein or glycoprotein
• Paracrystalline structure (Figure 2.31)
• Allows the archea to withstand strong osmotic pressure
• Serves as a filter to only allow solutes of lowe molecular
weight.
• Retain proteins near the cell surface (similar to gram -
bacteria)
• Resistant to lysozyme

A

S-Layers

85
Q

Cell Surface Structures:

• Polysaccharide layers (Figure 2.32)
• May be thick or thin, rigid or flexible
• Assist in attachment to surfaces- bacterial pathogenicity
- formation of biofilm
• Protect against phagocytosis
• Resist desiccation – enhancing bacterial virulence (ex.
B. anthracis and S. pneumoniae)

A

Capsules and slime layers

86
Q

• Filamentous protein structures (Figure 2.33)
• Enable organisms to stick to surfaces or form pellicles
(thin sheets of cells on a liquid surface) or biofilm
• Also enhances bacterial virulence as it assist disease
process (attachment to tissue)

A

Fimbriae

87
Q

• Filamentous protein structures (Figure 2.34)
• Typically longer than fimbriae
• Assist in surface attachment
• Facilitate genetic exchange between cells (conjugation)
• Type IV pili involved in twitching motility (a type of
gliding motility)
• Receptor for certain viruses

A

Pili

88
Q

Carbon storage polymers:
glucose polymer

A

Glycogen

89
Q

Carbon storage polymers:

accumulations of inorganic phosphate

A

Polyphosphates

90
Q

Carbon storage polymers:
composed of elemental sulfur stored in the periplasm

A

Sulfur globules

91
Q

Carbon storage polymers:
composed of barium, strontium, and magnesium

A

Carbonate minerals

92
Q

Carbon storage polymers:
magnetic storage inclusions (iron oxide mineral
magnetite Fe3O4

• Allows the bacterial cells to orient themselves within a magnetic field. Not observed in archea

A

Magnetosomes

93
Q

• Confer buoyancy in planktonic cells (Figure 2.39)
• Spindle-shaped, gas-filled structures made of protein
(Figure 2.40)
• Impermeable to water

A

Gas vesicles

94
Q

Gas vesicles are composed of two proteins:

A
  • GvpA (water tight vesicle shell)
  • GvpC (strengthen the shell of the gas vesicle)
95
Q

Function by decreasing cell density

A

Gas vesicles

96
Q

• Highly differentiated cells resistant to heat, harsh
chemicals, and radiation (Figure 2.42 )
• “Dormant” stage of bacterial life cycle (Figure 2.43)
• Ideal for dispersal via wind, water, or animal gut
• Present only in some gram-positive bacteria

A

Endospores

97
Q

• Structurally complex
• Contains dipicolinic acid
• Enriched in Ca2+
• Core contains small acid-soluble spore proteins (SASP)

A

Endospore structure

98
Q

• Complex series of events (Figure 2.47)
• Genetically directed

A

The sporulation process

99
Q

structure that assists in swimming

A

Flagella

100
Q

Different arrangements of flagella:

A

• peritrichous (everywhere)
• polar (on side)
• lophotrichous (many flagella on one side)

101
Q

Flagella shape

A

Helical in shape

102
Q

Flagellar structure of Bacteria:
Filament composed of different types of protein called __________.

A

flagellin

103
Q

Flagellar structure of Bacteria:
Move by _________.

A

rotation- like a propeller

104
Q

Flagella increase or decrease rotational speed in
relation to __________.

A

strength of the proton motive force

105
Q

Peritrichously flagellated cells move slowly in a __________.

A

straight line

106
Q

Polarly flagellated cells move more __________ and typically __________.

A

Rapidly; spin around

107
Q

• Flagella-independent motility (Figure 2.56)
• Slower and smoother than swimming
• Movement typically occurs along long axis of cell
• Requires surface contact
• Mechanisms
• Excretion of polysaccharide slime
• Type IV pili
• Gliding-specific proteins

A

Gliding motility

108
Q

__________ is a directed movement in response to chemical or physical gradients.

A

Taxis

109
Q

directed movement in response to chemicals

A

Chemotaxi

110
Q

directed movement in response to light

A

Phototaxis

111
Q

directed movement in response to oxygen

A

Aerotaxis

112
Q

directed movement in response to ionic strength

A

Osmotaxis

113
Q

directed movement in response to water

A

Hydrotaxis

114
Q

• Best studied in E. coli
• Bacteria respond to temporal, not spatial, difference in
chemical concentration
• “Run and tumble” behavior (Figure 2.57)
• Attractants and receptors sensed by chemoreceptors

A

Chemotaxis

115
Q

Contain a membrane-enclosed nucleus and other organelles (e.g., mitochondria, Golgi complex, endoplasmic reticula, microtubules, and microfilaments.

A

Eukaryotes

116
Q

contains the chromosomes

A

Nucleus

117
Q

DNA is wound around __________.

A

histones

118
Q

Site of ribosomal RNA synthesis

A

nucleolus

119
Q

• DNA is wound around histones
• Visible under light microscope without staining
• Enclosed by two membranes
• Within the nucleus is the nucleolus
• Site of ribosomal RNA synthesis

A

Nucleus:

120
Q

Cell division

• Normal form of nuclear division in eukaryotic cells
• Chromosomes are replicated and partitioned into two
nuclei.
• Results in two diploid daughter cells

A

Mitosis

121
Q

Cell division

• Specialized form of nuclear division
• Halves the diploid number to the haploid number
• Results in four haploid gametes

A

Meiosis

122
Q

All specialize in energy metabolism

A

Mitochondria, Hydrogenosomes, and
Chloroplast

123
Q

• Respiration and oxidative phosphorylation
• Bacterial dimensions (rod or spherical)
• Over 1,000 per animal cell
• Surrounded by two membranes
• Folded internal membranes called cristae
• Contain enzymes needed for respiration and ATP
production
• Innermost area of mitochondrion called matrix
• Contains enzymes for the oxidation of organic
compounds

A

Mitochondria

124
Q

Mitochondria :

Folded internal membranes called __________.

Contain enzymes needed for respiration and ATP
production

A

cristae

125
Q

Mitochondria :

Innermost area of mitochondrion called __________.

Contains enzymes for the oxidation of organic
compounds

A

matrix

126
Q

• 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

A

Hydrogenosome

127
Q

Chlorophyll-containing organelle found in phototrophic eukaryotes

A

Chloroplast

128
Q

Chloroplast :

Flattened membrane discs are __________.

A

thylakoids

129
Q

Chloroplast :

Lumen of the chloroplast is called the __________.

A

stroma

130
Q

Stroma contains large amounts of __________.

A

RubisCO

131
Q

RubisCO is key enzyme in _________.

A

Calvin cycle

132
Q

Chloroplasts and mitochondria suggested as
descendants of ancient prokaryotic cells called _________.

A

endosymbiosis

133
Q

Mitochondria and chloroplasts contain __________. Which is __________ in shape.

A

DNA; circular

134
Q

Eukaryotic nuclei contain genes derived from __________.

A

bacteria

135
Q

Endoplasmic reticulum (ER) Two types:

A

(smooth and rough)

136
Q

__________ ER that contains attached ribosomes;

A

Rough ER

137
Q

__________ ER that participates in the synthesis of lipids

A

Smooth ER

138
Q

__________ ER is a major producer of glycoproteins

A

Rough ER

139
Q

stacks of membrane
distinct from, but functioning in concert with, the
ER
• Modifies products of the ER destined for secretion

A

Golgi complex

140
Q

• Membrane-enclosed compartments
• Contain digestive enzymes used for hydrolysis
• Allow for lytic activity to occur within the cell without
damaging other cellular components

A

Lysosomes

141
Q

• 25 nm in diameter; composed of α- and β-tubulin
• Function in maintaining cell shape, in motility, in chromosome
movement, and in movement of organelles

A

Microtubules

142
Q

• 7 nm in diameter; polymers of actin
• Function in maintaining cell shape, motility by pseudopodia, and cell division

A

Microfilaments

143
Q

• 8–12 nm in diameter; keratin proteins
• Function in maintaining cell shape and positioning of
organelles in cell

A

Intermediate filaments

144
Q

• Organelles of motility allowing cells to move by swimming

A

Flagella and cilia

145
Q

Cilia are short __________.

A

Flagella

146
Q

Flagella and cilia are bundles of __________ pairs of microtubules surrounding the central pair

A

9

147
Q

What are the 6 major morphologies

A

Coccus
Rod
Spirillum
Spirochete
Budding and appendaged bacteria
Filamentous Bacteria

148
Q

What is the Largest Bacteria discovered?

A

Thiomargarita Namibiensis

MICROPARA [LEC] (3 decks)

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