Cell Structure & Function Flashcards
1
Q
What is visible light used for in compound light microscopy?
A
Illuminate cells
2
Q
What are 4 types of light microscopy?
A
1) Bright-field
2) Phase-contrast
3) Dark-field
4) Flourescence
3
Q
What are the 2 types of lenses in a bright-field microscope?
A
Ocular and objective
4
Q
What is the maximum magnification of a bright-field microscope?
A
2000x
5
Q
Define magnification
A
The ability to make an object larger
6
Q
Define resolution
A
The ability to distinguish two adjacent objects as separate and distinct
7
Q
How are magnification and resolution related?
A
Inversely
8
Q
How do you calculate magnification?
A
Ocular magnification times objective magnification
9
Q
What happens to resolution as wavelength decreases?
A
It increases
10
Q
What happens to resolution as energy decreases?
A
It decreases
11
Q
What is a way to improve contrast?
A
Staining
12
Q
What is simple staining?
A
Only one dye is used to colour a specimen
13
Q
Define chromophore
A
The coloured portion of a dye
14
Q
What is a basic dye?
A
- A positively charged chromophore
- Binds to negatively charged molecules on cell surface
15
Q
What is an acidic dye?
A
- Negatively charged chromophore
- Repelled by cell surface; stains background
16
Q
What are 3 examples of differential stains?
A
- The Gram stain
- Acid fast stain
- Endospore stain
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
18
Q
What does an acid fast stain detect?
A
Mycolic acid in the cell wall of Mycobacterium
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
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
21
Q
What does phase-contrast microscopy allow for the visualization of?
A
Live samples
22
Q
Does phase-contrast microscopy involve a stain?
A
No
23
Q
What kind of image will be produced by a phase-contrast microscope?
A
Dark cells on a light background
24
Q
What kind of image will be produced by a dark field microscope?
A
A bright object on a dark background
25
What is dark field microscopy used to observe?
Bacteria that don't stain well
26
What is fluorescence microscopy used to observe?
Specimens that fluoresce
27
What is the name of a fluorescent dye and what does it bind to?
DAPI binds to DNA
28
How can cells be observed in 3D?
By using differential interference contrast (DIC) microscopy or confocal scanning laser microscopy (CSLM)
29
What happens in a DIC microscope?
A polarizer is used to create two distinct beams of polarized light
30
What is the resolution for CSLM?
0.1 micrometer
31
What do electron microscopes use to image cells and structures?
Electrons
32
Since the wavelength of an electron is much shorter than the wavelength of light, what does that mean for resolution?
Higher resolution
33
What are the 2 types of electron microscopes?
1) Transmission electron microscope
| 2) Scanning electron microscope
34
What must be done to a cell before it can be viewed with a transmission electron microscope?
It must be fragmented (sliced) and then stained
35
What must a cell be stained with before it can be viewed with a transmission electron microscope and why?
Metals such as lead or uranium because they bind to cell structures and make them more electron dense
36
What must a cell be stained with before it can be viewed with a scanning electron microscope?
A thin film of heavy metal such as gold
37
Do prokaryotes have membrane bound organelles?
Nope
38
Between bacteria and archaea, which have the capacity to be pathogenic?
Bacteria
39
Are archaea ever pathogenic?
No
40
What is a coccus shape?
Spherical
41
What is a bacillus shape?
Rod
42
What is a spirillum shape?
Spiral
43
Is it common or uncommon for cells to have a shape that is not coccus, bacillus, or spirillum?
Uncommon
44
Can morphology (shape) predict any characteristics of a cell?
Generally no
45
What is an advantage to being small?
More surface area relative to cell volume
46
What does a greater surface-to-volume ratio mean?
- Greater nutrient exchange per unit cell volume
| - Tend to grow faster
47
What is generally the smallest a cell can be and still be able to live?
0.15 micrometer
48
What is another name for the cytoplasmic membrane?
Plasma membrane
49
On a phospholipid, which part is hydrophobic and which is hydrophilic?
Hydrophobic -- fatty acid tail
| Hydrophilic -- glycerol-phosphate head
50
Define amphipathic and give an example
- Has both polar and nonpolar characteristics
| - Ex: proteins embedded in the plasma membrane
51
What does an ester phospholipid consist of?
- Glycerol
- 2 fatty acids
- Phosphate
- Possibly a side chain
52
What is the general diameter of the cytoplasmic membrane?
8 - 10 nm
53
What stabilizes the plasma membrane?
Hydrogen bonds and hydrophobic interactions
54
Why is the plasma membrane fluid?
So protein channels can move from side to side
55
Does a gram negative or gram positive bacteria have an extra outer membrane?
Gram negative
56
Does the membrane proteins bind substrates and process large molecules for transporting gram-positive or gram-negative bacteria?
Gram negative
57
How are integral membrane proteins connected to the plasma membrane?
Firmly embedded in the membrane
58
How are peripheral membrane proteins connected to the plasma membrane?
One portion is anchored in the membrane
59
Where are ether linkages found?
Phospholipids in archaea
60
Where are ester linkages found?
Bacteria and Eukarya phospholipids
61
What is lacking in archaeal lipids and what replaces them?
Fatty acids replaced by isoprenes
62
Are arachaeal plasma membrane lipids always in a bilayer?
No, they can be a monolayer, bilayer, or a mixture
63
What is a major difference between lipid monolayers and lipid bilayers?
Monolayer membranes are extremely heat resistant
64
What kind of archaea are monolayers typically found in?
Hyperthermophilic (ones that live in environments over 80 C)
65
What types of molecules can cross the plasma membrane?
Polar and charged
66
What is the purpose of transport proteins?
Carry solutes against their concentration gradient
67
What does a protein anchor do?
Hold transport proteins in place
68
Do carrier-mediated systems happen for just any substance?
NO! They are highly specific
69
What are 3 major classes of transport systems in prokaryotes?
1) Simple transport
2) Group translocation
3) ABC system
70
Define uniporter
Transport in one direction across the membrane
71
Define symporter
Function as co-transporter (2 molecules going in the same direction across the membrane)
72
Define antiporter
Transport a molecule across the membrane while simultaneously transporting another molecule in the opposite direction
73
What does ABC stand for in ABC transport?
ATP-binding cassette
74
What is ABC transport involved in the uptake of?
Organic compounds, inorganic nutrients, and trace metals
75
What do gram-negatives employ for ABC transport?
Periplasmic-binding proteins
76
What do gram-positives employ for ABC transport?
Substrate-binding lipoproteins
77
What is the texture of the cell wall of bacteria and archaea?
Rigid to help determine cell shape
78
Is the cell wall of bacteria and archaea a major permeability barrier?
No
79
What is the main function of the cell wall in bacteria and archaea?
Protect the cell from osmotic changes
80
What is a bacteria cell relative to its surroundings?
Hypertonic, so H2O goes into the cell
81
What does the cell wall prevent?
Cell expansion and toxic substances
82
What are the differences in cell wall structure between gram-positives and gram-negatives?
- Gram-positive has only peptidoglycan
| - Gram-negative has peptidoglycan and LPS (lipopolysaccharide)
83
What does peptidoglycan do for the cell wall?
Provide strength
84
What is the backbone of peptidoglycan composed of?
NAM and NAG connected by glycosidic linkages
85
What is the difference between gram-positive and gram-negative peptidoglycan?
It is cross-linked differently
86
What is not present in the peptidoglycan of gram-negative bacteria?
An interbridge
87
Is NAG involved in interbridges?
Nope
88
What percentage of gram-positive cell walls is peptidoglycan?
Up to 90%
89
What is commonly embedded in the cell wall of gram-positives?
Teichoic acids
90
What are crosslinks in peptidoglycan formed by?
Peptides
91
What is the shape of a peptidoglycan strand?
Helical
92
What does LPS consist of?
Core polysaccharide and O-polysaccharide
93
What does LPS replace?
Phospholipids in outer half of outer membrane
94
What is periplasm?
The space located between cytoplasmic and outer membrane
95
What does periplasm contain?
Many proteins
96
What are porins?
Channels for movement of hydrophilic low-MW substances
97
Do archaeal cell walls have peptidoglycan and an outer membrane?
Not usually
98
What is found in the cell wall of some archaea?
Pseudomurein
99
What is the most common cell wall type of archaea?
S-layer
100
What does the S-layer consist of?
Protein or glycoprotein
101
What are archaea resistant to since they lack peptidoglycan?
Lysozyme and penicillin
102
Define cytoplasm
Material bounded by plasma membrane
103
Define protoplast
The plasma membrane and everything within it
104
Define nucleoid
The region that contains the genome
105
What kind of ribosome is found in bacteria?
70S
106
What kind if ribosome is found in eukarya?
80S
107
What components make up a ribosome?
30S small subunit (40S in eukarya) and 50S large subunit
108
What are capsules and slime layers made of?
Polysaccharides and proteins
109
What is the purpose of capsules and slime layers?
Assist in attachment to surface
110
What do capsules and slime layers protect against?
Phagocytosis and desiccation
111
What is the function of fimbriae?
Enable organisms to stick to surfaces or form pellicles
112
What are fimbriae?
Filamentous protein structures
113
What is the difference between fimbriae and pili?
Pili are typically longer
114
What is the function of pili?
Assist in surface attachment
115
What are inclusion bodies?
Aggregates in cytoplasm
116
What are polyphosphates?
Accumulations of inorganic phosphate
117
What are magnetosomes?
Magnetic storage inclusion bodies
118
What are polyphosphates used for?
Storage of phosphate and energy
119
What is the function of magnetosomes?
Give the cell magnetic properties, allowing it to orient itself in a magnetic field
120
What do gas vesicles do?
Convey bouyancy
121
What are gas vesicles made of?
Protein
122
HOW do gas vesicles function?
By decreasing cell density
123
What are gas vesicles impermeable to?
Water
124
What are endospores?
Highly differentiated cells resistant to heat, harsh chemicals, and radiation
125
What kind of bacteria produce endospores?
Some gram positives, NEVER GRAM NEGATIVES
126
Why is an endospore metabolically inactive?
It is dormant
127
Where is an endospore formed?
Inside a mother cell
128
What do the spore coat and cortex protect against?
Chemicals, enzymes, physical damage, and heat
129
What 5 things can endospores resist?
1) Boiling for hours
2) UV and gamma radiation
3) Chemical disinfectants
4) Desiccation
5) Age
130
What are the 7 stages of the life cycle of a spore-forming bacterium?
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
What does septation divide the cell into?
Forespore and mother cell
132
What is the core wall?
Highly cross-linked peptidoglycan layer
133
What is the cortex?
Loosely cross-linked peptidoglycan layer
134
What does the coat protect the spore from?
Chemicals and enzymes
135
What happens after the mother cell is lysed?
A mature spore is released
136
What are flagella and what do they do?
Hollow protein filaments that assist with motility
137
Define monotrichous
Single flagellum
138
Define amphitrichous
Flagella at opposite ends
139
Define lophotrichous
Multiple flagella in a single tuft
140
Define peritrichous
Flagella distributed all around cell
141
What 3 parts does a flagellum consist of?
1) Filament
2) Hook
3) Basal body
142
What are the 4 rings that the basal body passes through?
1) L ring -- LPS layer
2) P ring -- peptidoglycan
3) MS ring -- membrane
4) C ring -- cytoplasm
143
Where does energy to power the flagella come from?
Proton motive force
144
Where is there a high [H+]?
Outside the cytoplasmic membrane
145
Where is there a low [H+]?
Inside the cytoplasmic membrane
146
___ forms a channel that allows H+ to move into the cytoplasm
Mot proteins
147
What part of a flagella is made first?
MS ring
148
What part of a flagella is made last?
Filament
149
What does gliding motility require?
Surface contact
150
Define taxis
Directed movement in response to chemical or physical gradients
151
Define chemotaxis
Response to chemicals
152
Define phototaxis
Response to light
153
Define aerotaxis
Response to oxygen
154
Define osmotaxis
Response to ionic strength
155
Define hydrotaxis
Response to water (to rehydrate cell)
156
What are attractants and repellants sensed by in E. coli?
Chemoreceptors
157
How do you measure chemotaxis?
Insert a capillary tube containing an attractant or a repellent into a medium of motile bacteria
158
What do eukaryotic cells need since they have a lower surface area to volume ratio?
More sophisticated transport mechanisms
159
Give 5 pieces of evidence that support the hypothesis that mitchondria and chloroplasts evolved from bacteria.
1) Semi-autonomous
2) Circular chromosomes
3) 70S ribosomes
4) Two membranes
5) Outer membrane has porins
