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MBIO 1010 > Lecture 2: Cell Structure and Function > Flashcards

Lecture 2: Cell Structure and Function Flashcards

Cell Structure and Function

1
Q

four types of light microscopy:

A

bright-field
phase contrast
dark-field
fluorescence

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2
Q

________ scope
Specimens are visualized because of differences in contrast between specimen
and surroundings

Two sets of lenses form the image
* Objective lens (usually 10x -100x mag.) & ocular lens (usually 10x – 20x mag.)

A

Bright-field

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3
Q

how to calculate total magnification?

A

Total magnification = objective
magnification ✕ ocular magnification

  • Maximum magnification is ~2,000X
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4
Q

_______: the ability to make an object larger

A

Magnification

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5
Q

_______: the ability to distinguish two adjacent objects as separate and distinct

A

Resolution

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6
Q

what is the limit of resolution for a light microscope?

A

0.2 μm (wavelength of light source can’t fit through anything smaller)

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7
Q

every light source produces a ____

A

wavelength

low wavelength = high energy
high wavelength = low energy

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8
Q

as wavelength ____, resolution improves

A

decreases

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9
Q

improving contrast results in a better final image, how do we improve contrast?

A

staining! we use organic dyes (contain Carbon) that bind to specific cellular materials, common stains are methylene blue, safranin, and crystal
violet

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10
Q

________ – One dye used to color specimen

A

Simple staining, sticks to everything possible! (non-specific)

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11
Q

________: coloured portion of a dye

A

Chromophore

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12
Q

what are the two types of simple stains?

A

Basic dye – positively charged chromophore
* Binds to negatively charged molecules on cell
surface
Crystal violet – basic

Acidic dye – negatively charged chromophore
* Repelled by cell surface
* Used to stain background
* Negative stain

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13
Q

what charge does the cell surface have?

A

negative charge

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14
Q

what are the three types of differential stains?

A

gram stain, acid fast stain, endospore stain

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15
Q

______: Separates bacteria into 2 groups based on cell wall
structure

A

The gram stain

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16
Q

_______ – cells that
retain a primary stain, crystal violet
* Purple

A

Gram positive

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17
Q

_______ – cells that
lose the primary stain
* Take color of counterstain, safranin
* Red or pink

A

Gram negative

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18
Q

gram negative cells have how many membranes?

A

2

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19
Q

gram positive cells have how many membranes?

A

1

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20
Q

what are the four steps of a gram stain?

A

Step 1: Flood a heat-fixed smear with crystal violet for 1 minute (all cells are stained purple)
Step 2: Add iodine solution for 1 min (helps crystal violet stick)
Step 3: decolourize with alcohol briefly, washes of crystal violet that is on outer membrane of gram negative cells to make them colourless, gram positive cells remain purple
Step 4: Counterstain with safranin for 1-2 minutes, all cells will be dyed pink but Purple overshadows Pink…
this results in gram positive cells being purple, and gram negative cells being pink-red

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21
Q

_________:
* Detects mycolic acid in the cell wall of the genus Mycobacterium
* Mycobacterium– retains primary stain (Fuchsia (pink))
* Anything else on slide – colour of counterstain
* Blue

A

Acid fast stain

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22
Q

what does an acid fast stain detect in cell wall of Mycobacterium?

A

mycolic acid, dyes it pink!

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23
Q

_________:
* Endospores retain primary stain (Green)
* Cells counterstained (Pink)

A

Endospore stain

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24
Q

_______:
* 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 the visualization of live samples
  • Resulting image is dark cells on a light background
A

Phase-contrast microscopy

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25
Q

________:

  • Specimen is illuminated with a hollow cone of
    light
  • Only refracted light enters the objective
  • Specimen appears as a bright object on a dark
    background
  • Used to observe bacteria that don’t stain well
A

Dark field microscopy

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26
Q

_______:
* Used to visualize specimens that fluoresce
* Emit light of one color when illuminated with
another color of light

A

Fluorescence microscopy,
higher wavelength absorbed, lower wavelength emitted

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27
Q

true/false: cells may fluoresce naturally, or after staining with fluorescent dye

A

true!

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28
Q

__________ microscopy:
* Uses a polarizer to create two distinct beams of polarized light

  • Gives structures such as endospores, vacuoles, and granules a three-
    dimensional appearance
  • Structures not visible by bright-field microscopy are sometimes visible by _____
A

Differential interference contrast (DIC)

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29
Q

what are the two ways to image a cell in 3D?

A

Differential interference contrast (DIC) and Confocal scanning laser microscopy
(CSLM)

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30
Q

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

  • Computer can focus the laser on single
    layers of the specimen
  • Different layers can then be compiled for a
    three-dimensional image
  • Resolution is 0.1 μm
A

Confocal scanning laser microscopy
(CSLM)

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31
Q

Electron microscopes use electrons instead of ______ to image cells and structures

A

photons

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32
Q

Two types of electron microscopes?

A
  • Transmission electron microscopes (TEM)
  • Scanning electron microscopes (SEM)
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33
Q

_______:
Electron beam focused on
specimen by a condenser
* Magnets used as lenses

Electrons that pass through
the specimen are focused by
two sets of lenses
* Compound microscope

Electrons strike a fluorescent
viewing screen

A

Transmission Electron Microcope (TEM)

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34
Q

________: provided high magnification and resolution (0.2 nm) but the specimen but be very thin (20-60 nm) and must be stained with metals (lead or uranium)

A

TEM

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35
Q

how does staining specimen with metals help with visualization using TEM?

A

Bind to cell structures to make them more electron dense

Enables visualization of structures at molecular level

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36
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
* Allows an accurate 3D image of specimen’s surface.

A

Scanning Electron Microscopy (SEM)

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37
Q

what is a big difference between bacteria and archaea?

A

archaea are ALWAYS non-pathogens, bacteria can be pathogens OR non-pathogens

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38
Q

what are the three types of cell morphology? shapes?

A

coccus (roughly spherical)
bacillus (rod shaped)
spirillum (spiral shaped)

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39
Q

what are the other three forms of cell morphology?

A

cells with unusual shapes (spirochete)
budding and appendaged bacteria
filamentous bacteria

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40
Q

true/false: Morphology typically does not predict physiology, ecology,
phylogeny, etc. of a prokaryotic cell

A

true!

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41
Q

what are the selective forces that can set cell 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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42
Q

________ size:
Average:
* E. coli ~ 1.0 x 3.0 µm
* Staphylococcus aureus ~ 1.0 µm diameter

Very small:
* Mycoplasma genitalium~ 0.3 µm

Very large:
* Epulopiscium fishelsonii~ 80 x 600 µm.

A

prokaryote

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43
Q

what is the advantage to cells being very 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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44
Q

________:
* 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 (cell or plasma membrane)

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45
Q

Composition of ________:
* General structure is phospholipid bilayer

  • Contain both hydrophobic (fatty acid) and hydrophilic (glycerol-phosphate)
    components
  • Can exist in many different chemical forms as a result of variation in the
    groups attached to the glycerol backbone
  • Fatty acids point inward to form hydrophobic environment; hydrophilic
    portions remain exposed to external environment or the cytoplasm
A

membranes

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46
Q

ester phospholipids contain:

A

glycerol
2 fatty acids
phosphate
side chain (optional)

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47
Q

phospholipids are…

A

Amphipathic – has both polar
and non-polar characteristics

Polar: molecule carries full or partial charge
* Hydrophillic

Non-polar: molecule is
uncharged
* Hydrophobic

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48
Q

_________:
* 8–10 nm wide
* Embedded proteins
* Stabilized by hydrogen bonds and hydrophobic interactions
* Mg2+ and Ca2+ help stabilize membrane by forming ionic bonds with
negative charges on the phospholipids
* Somewhat fluid

A

Cytoplasmic membrane

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49
Q

In gram-negative bacteria, _______ interacts with a variety of proteins (periplasmic proteins) that bind substrates or process large molecules for transport

A

cytoplasmic membrane

because gram (-) have a double membrane, lots of space between membranes to interact!

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50
Q

Inner surface of cytoplasmic membrane interacts with proteins involved in
_______ and other important cellular functions

A

energy-yielding reactions
ex: ETC

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51
Q

______ membrane proteins
* Firmly embedded in the membrane

________ membrane proteins
* One portion anchored in the membrane

A

Integral
Peripheral

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52
Q

archaeal membranes have ____ linkages between phospholipids

bacteria/eukarya have ____ linkages in phospholipids

A

ether

ester

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53
Q

true/false: based on climate, archaea adjust their membrane structure

A

true!

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54
Q

what do archaeal lipids have instead of fatty acids?

A

isoprenes

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55
Q

what are the two types of major lipids

A

glycerol diethers
glycerol tetraethers

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56
Q

T/F: archaeal membranes can exist as lipid monolayers, bilayers, or mixtures

A

true! variation in thermal stability

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57
Q

what is the difference between a lipid bilyaer and monolayer?

A

there’s space between phsopholipids in a bilayer, no space in a monolayer

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58
Q

In contrast to lipid bilayers, lipid monolayer membranes are extremely _________

A

heat resistant

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59
Q

T/F: in extreme temperatures, DNA has less G-C content to increase thermal stability by increasing # of H-bonds

A

FALSE! G-C content would INCREASE if we were to increase # of H-bonds

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60
Q

_________ function:
Permeability barrier
* Polar and charged molecules must be transported
Transport proteins accumulate solutes against the concentration gradient

Protein anchor
* Holds transport proteins in place (cytoskeleton)

Energy conservation
* Generation of proton motive force

A

membrane

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61
Q

three major classes of transport systems in prokaryotes

A

simple transport
group translocation
ABC system

All require energy in
some form, usually
proton motive force
or ATP

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62
Q

________:
Driven by the energy
in the proton motive
force

A

Simple transport

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63
Q

__________:
Chemical modification
of the transported
substance driven by
phosphoenolpyruvate

A

Group translocation

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64
Q

________:
Periplasmic binding
proteins are involved
and energy comes
from ATP.

A

ABC transporter

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65
Q

_______ transport in one direction across the membrane

A

Uniporters

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66
Q

_______ function as co-transporters

A

Symporters

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67
Q

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

A

Antiporters

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68
Q

Simple transport:

Lac permease of Escherichia coli

  • Lactose is transported into E. coli by the simple transporter lac
    permease, a _______ – two molecules move across membrane in
    same direction
  • Activity of lac permease is energy-driven
  • Transports lactose and a H+ into the cell simultaneously
A

symporter

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69
Q

Group Translocation - e.g. __________ in E. coli

  • Sugar is phosphorylated during transport across the membrane
  • Moves glucose, fructose, and 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
A

phosphotransferase system

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70
Q

_________ transport systems

  • Involved in uptake of organic compounds (e.g., sugars, amino acids),
    inorganic nutrients (e.g., sulfate, phosphate), and trace metals
  • Typically display high substrate specificity
  • Gram-negatives employ periplasmic-binding proteins and ATP-driven
    transport proteins
  • Gram-positives employ substrate-binding lipoproteins (anchored to external surface of cell membrane) and ATP-driven transport proteins
A

ABC (ATP-binding cassette)

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71
Q

Outside the cell membrane

Rigid

Helps determine cell shape

Not a major permeability barrier

Porous to most small molecules

Protects the cell from osmotic
changes

A

cell walls of Bacteria and Archaea

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72
Q

______: prevents cell expansion – protects against osmotic lysis

  • Protects against toxic substances – large hydrophobic molecules
    Ex) detergents, antibiotics

Pathogenicity
* Helps evade host immune system
* Helps bacterium stick to surfaces

Partly responsible for cell shape

A

cell wall

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73
Q

gram (-) cell wall has…

A

two layers: outer membrane and peptidoglycan

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74
Q

gram (+) cell wall has…

A

one layer: peptidoglycan

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75
Q

_______:
Rigid layer that provides
strength to cell wall

Polysaccharide composed of:
* N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
* Amino acids
* Lysine or diaminopimelic acid
(DAP)
* Cross-linked differently in gram-
negative bacteria and gram-
positive bacteria
* Form glycan tetrapeptide

A

peptidoglycan

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76
Q

____ & ____ form disaccharide, creating lattice with amino acids to stabilize it

A

NAG and NAM

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77
Q

which one cross-links out of NAG and NAM?

A

only NAM

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78
Q

T/F: gram (+) have more layers of Nag/Nam

A

true! thicker peptidoglycan layer!

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79
Q

T/F: gram (-) have more layers of Nag/Nam AND an outer membrane

A

false! they have LESS because their layer of peptidoglycan is smaller due to the outer membrane being present

80
Q

T/F: More than 100 different PG structures identified, Vary in peptide cross-links
and/or interbridge

A

True!

81
Q

Gram-______ cell walls
* 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

A

positive

82
Q

________: teichoic
acids covalently bound to
membrane lipids

A

Lipoteichoic acids

83
Q

how are Nam and Nag connected in the backbone?

A

by glycosidic bonds

84
Q

peptidoglycan strand is _____

A

helical, allows for 3-dimensional cross-linking

85
Q

how many layers of peptidoglycan does E. Coli have?

A

One! because of presence of outer membrane (gram -)

86
Q

why don’t humans have cell walls/peptidoglycan if they provide so much protection?

A

we’re multicellular, it would take SO much energy to build cell walls around everything

87
Q

Prokaryotes that lack cell walls:
_______:
* Group of pathogenic bacteria
* Have sterols in cytoplasmic membrane – adds strength and rigidity to
membrane

_________:
* Species of Archaea
* Contain lipoglycans in membrane that have strengthening effect

A

Mycoplasmas
Thermoplasma

88
Q

LPS stands for…

A

lipopolysaccharide (LPS) layer
OR the outer membrane

89
Q

in gram negative bacteria, ~____% of cell wall contains peptidoglycan

A

10%

90
Q

LPS consists of _______ and ______
* LPS replaces most of phospholipids in outer half of outer membrane
* Endotoxin (lipid A): the toxic component of LPS

A

core polysaccharide and O-polysaccharide

91
Q

_______ (lipid A): the toxic component of LPS

A

Endotoxin

92
Q

endotoxin (lipid A) is a…

A

potent immune activator, causes a massive immune response which causes inflammation/vasodilation which leads to sepsis and organ failure

93
Q

_______: space located between cytoplasmic and outer membranes
* ~15 nm wide
* Contents have gel-like consistency
* Houses many proteins

A

Periplasm

94
Q

______: channels for movement of hydrophilic low-molecular-weight
substances

A

Porins

95
Q

how does alcohol wash prevent crystal violet stain from exiting peptidoglycan in gram (+) bacteria?

A

alcohol dehydrates cell walls so pores in wall close, trapping CV complex inside

96
Q

________ cell walls:
No peptidoglycan

Typically no outer membrane

Pseudomurein
* Polysaccharide similar to peptidoglycan
* Composed of N-acetylglucosamine and N-acetyltalosaminuronic acid
* Found in cell walls of certain methanogenic Archaea

A

archaeal

97
Q

T/F: Cell walls of some Archaea lack pseudomurein

A

true!

98
Q

why do archaea use pseudomurein instead of peptidoglycan?

A

their environment may not support peptidoglycan structure (extreme living conditions) so they use pseudomurein instead!

99
Q

_______:
* Most common cell wall type among
Archaea
* Consist of protein or glycoprotein
* Paracrystalline structure
* Some Archaea have only ______ (no other cell wall components)
* Most have additional cell wall elements

A

S-Layers

100
Q

T/F: Because they lack peptidoglycan, Archaea are resistant to
lysozyme and penicillin

A

true!

101
Q

______ – material bounded by plasma membrane (PM)

A

Cytoplasm

102
Q

_______ – PM and everything within
* Macromolecules – amino acids, nucleotides, etc
* Soluble proteins
* DNA and RNA (nucleoid)

A

Protoplast

103
Q

Proteins are made of polypeptides…
Polypeptide?

A

a long polymer of amino acids joined by peptide bonds

104
Q

_______:
Region that contains the genome

The typical bacterial genome:
* Single circular double stranded (ds) DNA
chromosome
* May have one or more plasmids
* Smaller circular dsDNA
* Self-replicating
* Carry non-essential genes
* Selective advantage
* Ex) Genes for antibiotic resistance

A

the Nucleoid

105
Q

______:
* Carries genetic info of all living cells
* Polymer of deoxyribonucleotides

A

DNA

106
Q

T/F: everything alive is single-stranded

A

FALSE! everything living is double-stranded…
viruses are single-stranded and are NOT living

107
Q

more evolved organisms have this type of ribosome

A

Plasma-membrane associated ribosomes

they’re membrane proteins that make proteins to be exported from the cell

108
Q

__________:

  • Polysaccharide / protein layers
  • May be thick or thin, rigid or flexible
  • Assist in attachment to surfaces
  • Protect against phagocytosis
  • Resist desiccation
A

Capsules and slime layers

109
Q

capsules and slime layers ae outside of…

A

EVERYTHING! plasma membrane AND cell wall

110
Q

T/F: capsule bacteria can’t be consumed by phagocytes

A

true! phagocytes have a standard for initial attachment that must be met- doesn’t include capsules

111
Q

______:
* Filamentous protein structures
* Enable organisms to stick to surfaces or form pellicles

A

Fimbriae

112
Q

_____:
* Filamentous protein structures
* Typically longer than fimbriae
* Assist in surface attachment
* Facilitate genetic exchange between cells (conjugation)
* Type IV ___ involved in twitching motility (by polymerizing/depolymerizing)

A

Pili

113
Q

____ are SUPER generous with genetic information which is not so good for humans, since they give away harmful information to pathogens that want to harm us!

A

pili

114
Q

pili can only give information using ______ transmission, not passed down to offspring

A

horizontal

115
Q

HOW do pili pass information?

A

using their hollow channel (pilus), connnects cytoplasmic environment of one cell to another

116
Q

_______:
Visible aggregates in cytoplasm

Carbon storage polymers
* Poly-β-hydroxybutyric acid (PHB): lipid
* Glycogen granules: glucose polymer

Polyphosphates: accumulations of inorganic phosphate

Sulfur globules: composed of elemental sulfur

Magnetosomes: magnetic storage inclusions

A

cell inclusion bodies

117
Q

_______: accumulations of inorganic phosphate

A

Polyphosphates

118
Q

_______: composed of elemental sulfur

A

Sulfur globules

119
Q

______: magnetic storage inclusions

A

Magnetosomes

120
Q

elemental sulfur is at what stage?

A

intermediate reduction stage

121
Q

we use carbon storage polymers for…

A

fight/flight! quick source of energy for blood glucose glycolysis from glycogen granules

122
Q

we use polyphosphates for….

A

storage of phosphate and energy

123
Q

we use sulfur globules for…

A

energy generation, oxidzied sulfur can be food for other molecules and sulfate can be an electron acceptor (ETC)

124
Q

we use magnetosomes…

A

to give the cell magnetic properties and allow it to orient itself in a magnetic field

125
Q

_______: magnetic movement

A

magnetotaxis

126
Q

________:
Confer buoyancy in planktonic cells

Spindle-shaped, gas-filled
structures made of protein

Function by decreasing cell density

Impermeable to water

A

Gas vesicles

127
Q

_______:
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

A

endospores

128
Q

only gram _____ can make endospores

A

positive

129
Q

T/F: endospores can survive extreme environments, only go into active form when conditions are ideal to them

A

true!

130
Q

a ______ cell is capable of normal growth, is metabolically active

A

vegetative

131
Q

an _____ is a dormant cell, formed inside of a mother cell

A

endospore

132
Q

endospores are triggered by….

A

lack of nutrients, takes about 8-10 hours

133
Q

Protective features of the endospore
______:
* Spore coat and cortex – protect against chemicals, enzymes, physical
damage, and heat
* Two membranes – permeability barriers against chemicals
_______:
* Dehydrated – protects against heat
* Ca-dipicolinic acid and SASPs
* Protect against DNA damage

A

Layers
Core

134
Q

T/F: endospores can resist
Boiling for hours
UV, g radiation
Chemical disinfectants
Dessication
Age

A

true!

135
Q

what are the seven stages of the lifecycle of a spore forming bacterium?

A

Stage 1: Asymmetric cell division
* DNA replicates
* Identical chromosomes pulled to opposite ends of the cell

Stage 2: Septation
* Divides cell into 2 unequal compartments:
* Forespore (prespore)
* Mother cell

Stage 3: Mother cell
engulfs the forespore
* Forespore surrounded by
two membranes

Stage 4: Formation of the cortex
* Thick layers of peptidoglycan form between the two membranes
* Highly cross-linked layer – core wall
* Loosely cross-linked layer – cortex (~½ of spore volume)

Stage 5: Coat synthesis
* Protein layers surround the core wall
* Spore coat
* Exosporium
* Protect the spore from chemicals and enzymes

Calcium, dipicolinic acid and small acid soluble proteins (SASPs) accumulate in
the core
* Help stabilize DNA

Stage 6: Endospore matures
* Core is dehydrated
* ~ 10 – 30% of a vegetative cell’s water
content

Stage 7: Mother cell is lysed
* Mother cell disintegrates
* Mature spore is released

136
Q

______:
hollow protein filaments
must be stained to view

A

flagella

137
Q

T/F: flagella can be used to support evidence for identification of bacteria

A

true! can be used for identification

138
Q

_______ – single flagellum
* Polar or subpolar

A

Monotrichous

139
Q

_________ – Flagella at opposite ends

A

Amphitrichous

140
Q

________ – Multiple flagella in a single tuft

A

Lophotrichous

141
Q

________ – Flagella distributed around cell

A

Peritrichous

142
Q

flagellar structure:

  1. ________
    * Rigid helical protein ~ 20 µm long
    * Composed of identical protein subunits –
    flagellin
  2. _______
    * Flexible coupling between filament and
    basal body
  3. ________ (motor)
    * Consists of central rod that passes through
    series of rings:
    * L ring – LPS layer
    * P ring – Peptidoglycan
    * MS ring – Membrane
    * C – ring – Cytoplasm (associated
    with membrane).
A

Filament
Hook
Basal Body

143
Q

T/F: flagella have different basal body structures for gram (+) vs. gram (-)

A

true!

144
Q

Energy to turn the flagella comes from the _________
* Gradient of protons (H+) across the
cytoplasmic membrane
* High [H+] outside
* Low [H+] inside

A

proton motive force (PMF)

145
Q

_____ proteins form a channel that allows H+ to move into the cytoplasm
* Provides the energy to turn the flagellum

A

Mot

146
Q

flagellum turn like a ______ to drive the cell forward

A

propeller

147
Q

steps of flagella synthesis:

A

several genes are required…

MS ring is made first
then other proteins and hook are made next
filament grows from tip and pushes cap upwards

148
Q

________
flagellated cells move
slowly in a straight line

A

Peritrichously, filaments are all over circumference of cell

149
Q

______ flagellated cells
move more rapidly and
typically spin around

A

Polarly

150
Q

_______ : Flagella-independent motility

A

gliding motility

151
Q

________ is…
Slower and smoother than swimming
* Requires surface contact
* Mechanisms
* Excretion of polysaccharide slime
* Type IV pili (twitching)
* Gliding-specific proteins

A

gliding motility

152
Q

why does gliding motility require surface contact?

A

for H bonds, Van der Waals interactions and electrostatic interactions

153
Q

______: response to chemicals

A

Chemotaxis, relative to a chemical (could be an attractant or a repellent)

154
Q

______: response to light

A

Phototaxis

155
Q

_____: response to oxygen

A

Aerotaxis

156
Q

______: response to ionic strength
obligate anaerobes must avoid oxygen because its toxic to them!

A

Osmotaxis
hypertonic env. = risk of dehydration
hypotonic env. = risk of bursting
isotonic = ideal

157
Q

______: response to water

A

Hydrotaxis

158
Q

in chemotaxis, bacteria respond to temporal NOT ______ difference in chemical

A

spatial

159
Q

if there’s no attractant chemical present, bacteria move in random movement but if there’s an attractant present…

A

directed movement, chemotaxis

160
Q

bacteria use a ______ walk to move away/towards attractant/repellent

A

biased random walk, they move in the right direction but randomly (still runs and tumbles)

161
Q

how do we measure chemotaxis?

A

by inserting a capillary tube containing an attractant or a
repellent in a medium of motile bacteria
then see how many go into/away from the tube!

162
Q

_______ have:
Lower surface area to volume
ratio

Need more sophisticated
transport mechanisms

Grow slower

A

Eukaryotes

163
Q

________:
Genetic material is housed in
a nucleus

Generally larger than
prokaryotes

Complex internal structure

Membrane bound
organelles

Intra-cytoplasmic membranes used for transport

Cytoskeleton

Divide by mitosis and meiosis

A

Eukaryotes

164
Q

________
* Site of photosynthesis
* Chlorophyll
* Surrounded by 2 membranes
* DNA (single circular) and ribosomes (70S)

A

Chloroplasts

165
Q

chloroplasts used to be a gram ____ bacteria!

A

negative

166
Q

_______
* Site of respiration and oxidative
phosphorylation
* Surrounded by 2 membranes
* DNA (single circular) and ribosomes (70S)

A

Mitochondria

167
Q

mitochondria used to be a gram _____ bacteria!

A

negative!

168
Q

______ evolved from bacteria
* Evidence
* Semi-autonomous
* Circular chromosomes
* Lack histones
* 70S ribosomes
* Two membranes
* Outer membrane has porins

A

Mitochondria and chloroplasts

169
Q

outer membranes of Mitochondria and chloroplasts have porins, this feature in indicative of what bacterial origin?

A

gram negative !

170
Q

_______:
* Most closely related to Rickettsia
* Proteobacteria
* Obligate intracellular pathogens
* Ex) Rocky-mountain spotted fever

A

Mitochondria

171
Q

_______:
* Most closely related to
Cyanobacteria
* Blue-green algae

A

Chloroplasts

172
Q

_______:
Acellular infectious particles

Obligate intracellular pathogens

Reproduce only inside of living
cells

Lack independent metabolism

Composed of at least 2 parts:

Nucleic acid genome (DNA or RNA) and protein coat (capsid)
* Together = Nucleocapsid

A

viruses

173
Q

Some ____ have an envelope – layer of lipid surrounding the
nucleocapsid

A

viruses

174
Q

the envelope surrounding some viruses is NOT a plasma membrane, what is it?

A

phospholipid bilayer

175
Q

what makes an enveloped virus so hard to identify in our systems?

A

the envelope has some of our proteins in it, so he can’t be identified!

176
Q

______ genomes:
DNA or RNA- never both

Single stranded or double stranded

Circular or linear

Can be in several pieces – segmented

Genome size
* Smallest ~ 3.6 kb for some ssRNA viruses (3 genes)
* Largest > 150 kbp for some dsDNA viruses (> 100 genes)

A

viral

177
Q

DNA viruses infiltrate the _____

A

nucleus- SUPER dangerous

178
Q

______– Protein coat that surrounds the genome

Allows transfer of viral genome between host cells

Made of identical polypeptides – protomers

Helical capsids
* Protomers form a spiral cylinder
* Nucleic acid genome coiled inside
* Ex. Tobacco mosaic virus capsid is
made of ~ 2100 identical protomers.

A

Capsid

179
Q

_______ capsids
* Regular geometric shape with 20 triangular faces
* Exhibit symmetry
* Protomers aggregate to form
capsomeres
* Ex. Human papillomaviruses
have form their capsids from
pentamers (clusters of 5)

A

Icosahedral

180
Q

_______
* Geometric head with an attached helical
tail
* Genome is carried in a polyhedral head, helical tail is used to inject DNA into a host
cell

A

Binal capids

181
Q

_________ large DNA viruses
* Viruses with complex multi-layered structure
* 0.75 µm in diameter, 1200 kbp DNA
* Larger than some bacteria

A

Nucleocytoplasmic

182
Q

_____ – a lipid bilayer surrounding the nucleocapsid that was acquired from the host membrane

A

Envelope
LOOKS like a plasma membrane because it CAME from one

183
Q

enveloped viruses are easier to destroy than naked viruses, because….

A

if we destroy the envelope, we automatically destroy the viruses key

184
Q

_______:
Consists of host lipids and viral proteins – spikes
Ex. Influenza virus

Flexible helical capsid, surrounded by an envelope

Two major spikes: hemaglutanin (H) and neuraminidase (N)

A

envelope

185
Q

________ (phage) – viruses that
infect bacteria

A

Bacteriophage

186
Q

T/F: viruses infect all domains of life

A

true!

187
Q

____ – infect and multiply only
inside of animal cells

A

Animal viruses

188
Q

T/F: viruses can jump species barrier through mutations

A

true!

189
Q

T/F: Most viruses are specific to a single host
species

A

true

190
Q

Virus must attach to _______ receptors on the host cell surface

A

specific

191
Q

T/F: Some viruses infect more than one species

A

true!

192
Q

steps of viral replication cycle:

A
  1. Adsorption – attachment to the host cell
    * Involves specific receptors on the host cell surface
    * Ex) LPS, outer membrane proteins or glycoproteins
  2. Penetration and uncoating – entry into the host cell
    * Bacteriophage – usually inject their nucleic acid into the cell
    * Leave the capsid outside the cell as a “ghost”
  3. Synthesis of viral nucleic acids and protein
    * Viral genes are expressed and viral proteins are synthesized (by the host’s
    own ribosomes)
    * Viral genome is replicated (by the host’s replication machinery)
  4. Assembly of new virions
    * Viral proteins are assembled into capsids, and then genomes are packaged
    into nucleocapsids
    * Viruses do not reproduce by division
  5. Release of new virions
    * Two basic strategies:
    i. Naked viruses usually accumulate, eventually lysing the host cell to
    release progeny – lytic infection
    ii. Enveloped viruses are usually released by budding
    * Virions push through the cytoplasmic membrane without killing
    the host cell – persistent infection
193
Q

entry into the cell by animal viruses:

A

Fusion with the plasma
membrane (unique to enveloped viruses)

Endocytosis
* Binding to specific receptors
triggers normal endocytic
activity

In either case, once inside:
* The capsid is removed
* Viral genome is released into the cell

194
Q

naked viruses MUST enter the cell using what entry method

A

endocytosis

195
Q

enveloped viruses can enter the cell using which two techniques?

A

fusion with the plasma membrane OR endocytosis

196
Q

________ – release of enveloped viruses
* Viral proteins inserted into the host membrane – Spikes
* Nucleocapsid associates with the spikes, and buds through the
membrane to form the envelope

A

Budding

197
Q

how does influenza use budding to release enveloped viruses?

A

Neuraminidase (N)
Allows new virions
to exit the host cell

Hemagglutanin (H)
Allows viruses to
adsorb to the next
host

MBIO 1010 (12 decks)

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