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Microbio 1010 > Cell Structure & Function > Flashcards

Cell Structure & Function Flashcards

1
Q

What is visible light used for in compound light microscopy?

A

Illuminate cells

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2
Q

What are 4 types of light microscopy?

A

1) Bright-field
2) Phase-contrast
3) Dark-field
4) Flourescence

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3
Q

What are the 2 types of lenses in a bright-field microscope?

A

Ocular and objective

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4
Q

What is the maximum magnification of a bright-field microscope?

A

2000x

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5
Q

Define magnification

A

The ability to make an object larger

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6
Q

Define resolution

A

The ability to distinguish two adjacent objects as separate and distinct

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7
Q

How are magnification and resolution related?

A

Inversely

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8
Q

How do you calculate magnification?

A

Ocular magnification times objective magnification

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9
Q

What happens to resolution as wavelength decreases?

A

It increases

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10
Q

What happens to resolution as energy decreases?

A

It decreases

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11
Q

What is a way to improve contrast?

A

Staining

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12
Q

What is simple staining?

A

Only one dye is used to colour a specimen

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13
Q

Define chromophore

A

The coloured portion of a dye

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14
Q

What is a basic dye?

A
  • A positively charged chromophore

- Binds to negatively charged molecules on cell surface

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15
Q

What is an acidic dye?

A
  • Negatively charged chromophore

- Repelled by cell surface; stains background

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16
Q

What are 3 examples of differential stains?

A
  • The Gram stain
  • Acid fast stain
  • Endospore stain
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17
Q

During a gram stain, what colour will the gram positive cell be and what colour will the gram negative cell be?

A
  • Gram positive is purple

- Gram negative is pink

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18
Q

What does an acid fast stain detect?

A

Mycolic acid in the cell wall of Mycobacterium

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19
Q

In an acid fast stain, what colour will the Mycobacterium be and what colour will everything else on the slide be?

A
  • Mycobacterium will be pink

- Everything else will be blue

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20
Q

In an endospore stain, what colour will the endospores be and what colour will all the other cells be?

A
  • Endospores will be green

- Other cells will be pink

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21
Q

What does phase-contrast microscopy allow for the visualization of?

A

Live samples

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22
Q

Does phase-contrast microscopy involve a stain?

A

No

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23
Q

What kind of image will be produced by a phase-contrast microscope?

A

Dark cells on a light background

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24
Q

What kind of image will be produced by a dark field microscope?

A

A bright object on a dark background

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25
Q

What is dark field microscopy used to observe?

A

Bacteria that don’t stain well

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26
Q

What is fluorescence microscopy used to observe?

A

Specimens that fluoresce

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27
Q

What is the name of a fluorescent dye and what does it bind to?

A

DAPI binds to DNA

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28
Q

How can cells be observed in 3D?

A

By using differential interference contrast (DIC) microscopy or confocal scanning laser microscopy (CSLM)

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29
Q

What happens in a DIC microscope?

A

A polarizer is used to create two distinct beams of polarized light

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30
Q

What is the resolution for CSLM?

A

0.1 micrometer

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31
Q

What do electron microscopes use to image cells and structures?

A

Electrons

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32
Q

Since the wavelength of an electron is much shorter than the wavelength of light, what does that mean for resolution?

A

Higher resolution

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33
Q

What are the 2 types of electron microscopes?

A

1) Transmission electron microscope

2) Scanning electron microscope

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34
Q

What must be done to a cell before it can be viewed with a transmission electron microscope?

A

It must be fragmented (sliced) and then stained

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35
Q

What must a cell be stained with before it can be viewed with a transmission electron microscope and why?

A

Metals such as lead or uranium because they bind to cell structures and make them more electron dense

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36
Q

What must a cell be stained with before it can be viewed with a scanning electron microscope?

A

A thin film of heavy metal such as gold

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37
Q

Do prokaryotes have membrane bound organelles?

A

Nope

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38
Q

Between bacteria and archaea, which have the capacity to be pathogenic?

A

Bacteria

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39
Q

Are archaea ever pathogenic?

A

No

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40
Q

What is a coccus shape?

A

Spherical

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41
Q

What is a bacillus shape?

A

Rod

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42
Q

What is a spirillum shape?

A

Spiral

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43
Q

Is it common or uncommon for cells to have a shape that is not coccus, bacillus, or spirillum?

A

Uncommon

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44
Q

Can morphology (shape) predict any characteristics of a cell?

A

Generally no

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45
Q

What is an advantage to being small?

A

More surface area relative to cell volume

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46
Q

What does a greater surface-to-volume ratio mean?

A
  • Greater nutrient exchange per unit cell volume

- Tend to grow faster

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47
Q

What is generally the smallest a cell can be and still be able to live?

A

0.15 micrometer

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48
Q

What is another name for the cytoplasmic membrane?

A

Plasma membrane

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49
Q

On a phospholipid, which part is hydrophobic and which is hydrophilic?

A

Hydrophobic – fatty acid tail

Hydrophilic – glycerol-phosphate head

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50
Q

Define amphipathic and give an example

A
  • Has both polar and nonpolar characteristics

- Ex: proteins embedded in the plasma membrane

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51
Q

What does an ester phospholipid consist of?

A
  • Glycerol
  • 2 fatty acids
  • Phosphate
  • Possibly a side chain
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52
Q

What is the general diameter of the cytoplasmic membrane?

A

8 - 10 nm

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53
Q

What stabilizes the plasma membrane?

A

Hydrogen bonds and hydrophobic interactions

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54
Q

Why is the plasma membrane fluid?

A

So protein channels can move from side to side

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55
Q

Does a gram negative or gram positive bacteria have an extra outer membrane?

A

Gram negative

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56
Q

Does the membrane proteins bind substrates and process large molecules for transporting gram-positive or gram-negative bacteria?

A

Gram negative

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57
Q

How are integral membrane proteins connected to the plasma membrane?

A

Firmly embedded in the membrane

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58
Q

How are peripheral membrane proteins connected to the plasma membrane?

A

One portion is anchored in the membrane

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59
Q

Where are ether linkages found?

A

Phospholipids in archaea

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60
Q

Where are ester linkages found?

A

Bacteria and Eukarya phospholipids

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61
Q

What is lacking in archaeal lipids and what replaces them?

A

Fatty acids replaced by isoprenes

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62
Q

Are arachaeal plasma membrane lipids always in a bilayer?

A

No, they can be a monolayer, bilayer, or a mixture

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63
Q

What is a major difference between lipid monolayers and lipid bilayers?

A

Monolayer membranes are extremely heat resistant

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64
Q

What kind of archaea are monolayers typically found in?

A

Hyperthermophilic (ones that live in environments over 80 C)

65
Q

What types of molecules can cross the plasma membrane?

A

Polar and charged

66
Q

What is the purpose of transport proteins?

A

Carry solutes against their concentration gradient

67
Q

What does a protein anchor do?

A

Hold transport proteins in place

68
Q

Do carrier-mediated systems happen for just any substance?

A

NO! They are highly specific

69
Q

What are 3 major classes of transport systems in prokaryotes?

A

1) Simple transport
2) Group translocation
3) ABC system

70
Q

Define uniporter

A

Transport in one direction across the membrane

71
Q

Define symporter

A

Function as co-transporter (2 molecules going in the same direction across the membrane)

72
Q

Define antiporter

A

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

73
Q

What does ABC stand for in ABC transport?

A

ATP-binding cassette

74
Q

What is ABC transport involved in the uptake of?

A

Organic compounds, inorganic nutrients, and trace metals

75
Q

What do gram-negatives employ for ABC transport?

A

Periplasmic-binding proteins

76
Q

What do gram-positives employ for ABC transport?

A

Substrate-binding lipoproteins

77
Q

What is the texture of the cell wall of bacteria and archaea?

A

Rigid to help determine cell shape

78
Q

Is the cell wall of bacteria and archaea a major permeability barrier?

A

No

79
Q

What is the main function of the cell wall in bacteria and archaea?

A

Protect the cell from osmotic changes

80
Q

What is a bacteria cell relative to its surroundings?

A

Hypertonic, so H2O goes into the cell

81
Q

What does the cell wall prevent?

A

Cell expansion and toxic substances

82
Q

What are the differences in cell wall structure between gram-positives and gram-negatives?

A
  • Gram-positive has only peptidoglycan

- Gram-negative has peptidoglycan and LPS (lipopolysaccharide)

83
Q

What does peptidoglycan do for the cell wall?

A

Provide strength

84
Q

What is the backbone of peptidoglycan composed of?

A

NAM and NAG connected by glycosidic linkages

85
Q

What is the difference between gram-positive and gram-negative peptidoglycan?

A

It is cross-linked differently

86
Q

What is not present in the peptidoglycan of gram-negative bacteria?

A

An interbridge

87
Q

Is NAG involved in interbridges?

A

Nope

88
Q

What percentage of gram-positive cell walls is peptidoglycan?

A

Up to 90%

89
Q

What is commonly embedded in the cell wall of gram-positives?

A

Teichoic acids

90
Q

What are crosslinks in peptidoglycan formed by?

A

Peptides

91
Q

What is the shape of a peptidoglycan strand?

A

Helical

92
Q

What does LPS consist of?

A

Core polysaccharide and O-polysaccharide

93
Q

What does LPS replace?

A

Phospholipids in outer half of outer membrane

94
Q

What is periplasm?

A

The space located between cytoplasmic and outer membrane

95
Q

What does periplasm contain?

A

Many proteins

96
Q

What are porins?

A

Channels for movement of hydrophilic low-MW substances

97
Q

Do archaeal cell walls have peptidoglycan and an outer membrane?

A

Not usually

98
Q

What is found in the cell wall of some archaea?

A

Pseudomurein

99
Q

What is the most common cell wall type of archaea?

A

S-layer

100
Q

What does the S-layer consist of?

A

Protein or glycoprotein

101
Q

What are archaea resistant to since they lack peptidoglycan?

A

Lysozyme and penicillin

102
Q

Define cytoplasm

A

Material bounded by plasma membrane

103
Q

Define protoplast

A

The plasma membrane and everything within it

104
Q

Define nucleoid

A

The region that contains the genome

105
Q

What kind of ribosome is found in bacteria?

A

70S

106
Q

What kind if ribosome is found in eukarya?

A

80S

107
Q

What components make up a ribosome?

A

30S small subunit (40S in eukarya) and 50S large subunit

108
Q

What are capsules and slime layers made of?

A

Polysaccharides and proteins

109
Q

What is the purpose of capsules and slime layers?

A

Assist in attachment to surface

110
Q

What do capsules and slime layers protect against?

A

Phagocytosis and desiccation

111
Q

What is the function of fimbriae?

A

Enable organisms to stick to surfaces or form pellicles

112
Q

What are fimbriae?

A

Filamentous protein structures

113
Q

What is the difference between fimbriae and pili?

A

Pili are typically longer

114
Q

What is the function of pili?

A

Assist in surface attachment

115
Q

What are inclusion bodies?

A

Aggregates in cytoplasm

116
Q

What are polyphosphates?

A

Accumulations of inorganic phosphate

117
Q

What are magnetosomes?

A

Magnetic storage inclusion bodies

118
Q

What are polyphosphates used for?

A

Storage of phosphate and energy

119
Q

What is the function of magnetosomes?

A

Give the cell magnetic properties, allowing it to orient itself in a magnetic field

120
Q

What do gas vesicles do?

A

Convey bouyancy

121
Q

What are gas vesicles made of?

A

Protein

122
Q

HOW do gas vesicles function?

A

By decreasing cell density

123
Q

What are gas vesicles impermeable to?

A

Water

124
Q

What are endospores?

A

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

125
Q

What kind of bacteria produce endospores?

A

Some gram positives, NEVER GRAM NEGATIVES

126
Q

Why is an endospore metabolically inactive?

A

It is dormant

127
Q

Where is an endospore formed?

A

Inside a mother cell

128
Q

What do the spore coat and cortex protect against?

A

Chemicals, enzymes, physical damage, and heat

129
Q

What 5 things can endospores resist?

A

1) Boiling for hours
2) UV and gamma radiation
3) Chemical disinfectants
4) Desiccation
5) Age

130
Q

What are the 7 stages of the life cycle of a spore-forming bacterium?

A

1) Asymmetric cell division
2) Septation
3) Mother cell engulfs the forespore
4) Formation of the cortex
5) Coat synthesis
6) Endospore matures
7) Mother cell is lysed

131
Q

What does septation divide the cell into?

A

Forespore and mother cell

132
Q

What is the core wall?

A

Highly cross-linked peptidoglycan layer

133
Q

What is the cortex?

A

Loosely cross-linked peptidoglycan layer

134
Q

What does the coat protect the spore from?

A

Chemicals and enzymes

135
Q

What happens after the mother cell is lysed?

A

A mature spore is released

136
Q

What are flagella and what do they do?

A

Hollow protein filaments that assist with motility

137
Q

Define monotrichous

A

Single flagellum

138
Q

Define amphitrichous

A

Flagella at opposite ends

139
Q

Define lophotrichous

A

Multiple flagella in a single tuft

140
Q

Define peritrichous

A

Flagella distributed all around cell

141
Q

What 3 parts does a flagellum consist of?

A

1) Filament
2) Hook
3) Basal body

142
Q

What are the 4 rings that the basal body passes through?

A

1) L ring – LPS layer
2) P ring – peptidoglycan
3) MS ring – membrane
4) C ring – cytoplasm

143
Q

Where does energy to power the flagella come from?

A

Proton motive force

144
Q

Where is there a high [H+]?

A

Outside the cytoplasmic membrane

145
Q

Where is there a low [H+]?

A

Inside the cytoplasmic membrane

146
Q

___ forms a channel that allows H+ to move into the cytoplasm

A

Mot proteins

147
Q

What part of a flagella is made first?

A

MS ring

148
Q

What part of a flagella is made last?

A

Filament

149
Q

What does gliding motility require?

A

Surface contact

150
Q

Define taxis

A

Directed movement in response to chemical or physical gradients

151
Q

Define chemotaxis

A

Response to chemicals

152
Q

Define phototaxis

A

Response to light

153
Q

Define aerotaxis

A

Response to oxygen

154
Q

Define osmotaxis

A

Response to ionic strength

155
Q

Define hydrotaxis

A

Response to water (to rehydrate cell)

156
Q

What are attractants and repellants sensed by in E. coli?

A

Chemoreceptors

157
Q

How do you measure chemotaxis?

A

Insert a capillary tube containing an attractant or a repellent into a medium of motile bacteria

158
Q

What do eukaryotic cells need since they have a lower surface area to volume ratio?

A

More sophisticated transport mechanisms

159
Q

Give 5 pieces of evidence that support the hypothesis that mitchondria and chloroplasts evolved from bacteria.

A

1) Semi-autonomous
2) Circular chromosomes
3) 70S ribosomes
4) Two membranes
5) Outer membrane has porins

Microbio 1010 (8 decks)

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