1
Q
what is a microscope?
A
an instrument that allows you to magnify an object
2
Q
what was the first type of microscope?
A
light microscopes
3
Q
give examples of safety precautions to follow when using a microscope
A
- good lifting posture when moving microscope
- do not reflect sunlight through the lenses (if microscope has a mirror), causes retina damage
- do not touch the light source, burns
- iodine solution stains skin/clothing, do not touch it
- methylene blue is harmful when swallowed, do not ingest it
4
Q
what is cell theory?
A
both plant and animal tissue is composed of cells
cells are the basic unit of all life
cells only develop from existing cells
5
Q
what are the four kinds of slide/mounts?
A
dry mount
wet mount
squash slides
smear slides
6
Q
how do you prepare a dry mount?
A
- solid specimen
- viewed whole/cut into very thin slices with a sharp blade (sectioning)
- specimen placed on centre of the slide, coverslip on top
7
Q
how do you prepare a wet mount?
A
- specimens suspended in a liquid
- coverslip placed on from an angle
8
Q
how do you prepare a squash slide?
A
- wet mount prepared
- lens tissue used to gently press down the cover slip
9
Q
what kind of sample is a quash slide good for?
A
soft samples
10
Q
how do you prepare a smear slide?
A
- edge of a slide used to smear the sample
- creating a thin/even coating on another slide
- cover slip placed on top
11
Q
how do stains increase contrast between cells/cell structures?
A
different components take up stains to different degrees, making the appear different shades/colours
12
Q
why is the increase in contrast provided by stains useful when viewing specimen?
A
allows components that would have otherwise been hard to differentiate/see to become visible so they can be identified
13
Q
how do you prepare a sample for staining?
A
- sample placed on a slide and allowed to air dry
- heat-fixed by passing through a flame
- specimen will adhere to the microscope slide
14
Q
what are the two ways in which stains work?
A
- stain colours some parts of the cells more strongly than others
- stain colours certain part of a cell by reacting with chemicals in it
15
Q
what are the two main positively charged dyes?
A
crystal violet
methylene blue
16
Q
how do positively charged dyes work?
A
they are attracted to negatively charged material in the cytoplasm, leading to the staining of certain cell components
17
Q
what are the main two negatively charged dyes?
A
Congo red
nigrosin
18
Q
how do negatively charged dyes work?
A
repelled by negatively charged cytosol, instead remaining outside of the cell (leaving it unstained). this allows the cell to stand out against the background - negative staining
19
Q
what is the gram stain technique?
A
a staining technique that separates bacteria into two groups
20
Q
what are the steps of the gram staining technique?
A
1) crystal violet applied, then iodine to fix the dye
2) slide washed with alcohol
3) gram positive bacteria retains the crystal violet stain, appearing blue/purple
4) gram negative bacteria lose the stain
5) then stained with safranin dye (counterstain)
6) this makes gram negative bacteria appear red
21
Q
what type of gram bacteria is susceptible to penicillin, and why?
A
gram positive, has thicker cell walls
22
Q
why does gram negative bacteria lose the crystal violet stain?
A
they have thinner cell walls
23
Q
what counterstain is used in the gram stain technique?
A
safranin dye
24
Q
what is the acid-fast staining technique?
A
staining technique used to differentiate species of mycobacterium from other bacteria
25
what are the steps of the acid-fast staining technique?
1) lipid solvent used to carry carbolfuchsin dye into cells
2) cells washed with dilute acid-alcohol solution
3) mycobacterium retain the stain, appearing bright red
4) other bacteria lose the stain and are then exposed to methylene blue, appearing blue
26
what is the name of the first dye used in the acid-fast technique?
carbolfuchsin dye
27
what are the four steps involved in the production of pre-prepared slides?
fixing
sectioning
staining
mounting
28
describe the process of fixing a specimen when pre-preparing slides
chemicals, i.e. formaldehyde, used to preserve specimens in as near-natural of a state as possible
29
describe the process of sectioning a specimen when pre-preparing slides
specimens are dehydrated with alcohols, then placed in a mould with wax/resin to form a hard block. this is then thinly sliced with a microtome
30
what is a microtome?
the knife used to thinly slice specimens preserved in wax/resin during slide preperation
31
describe the process of staining a specimen when pre-preparing slides
the specimen is treated with multiple stains to show the various different cell structures
32
describe the process of mounting a specimen when pre-preparing slides
specimen secured to a microscope slide and a coverslip placed on top
33
what is a mount?
a microscope slide that displays a specimen
34
what is a temporary mount?
a specimen emerged in a liquid that soon evaporates, causing the specimen to dry out and therefore distort the cells
35
why do electron microscopes have higher resolution than light microscopes?
electron beams have a shorter wavelength than light waves, meaning that individual beams can be much closer before they overlap. therefore, objects which are smaller/closer can be seen separately without diffraction blurring the image
36
what are the four types of microscopes?
light, confocal, TEM and SEM
37
what is the max resolution of light microscopes?
x1500-2000
38
what is the max resolving power of light microscopes?
200nm
39
light microscopes use _ _ to illuminate a thin section of sample
visible light
40
what is the focusing method of light microscopes?
glass lenses / mirrors / prisms
41
in light microscopes, energy is _
transmitted
42
give examples of stains used for light microscopes
methylene blue / crystal violet / iodine
43
what type of image is obtained from a light microscope?
colour, 2D, low res
44
what are the advantages of using light microscopes?
able to view living specimen
inexpensive
portable
accessible
45
what is the main disadvantage of light microscopes?
low resolution images compared to electron microscopes
46
laser scanning (confocal) microscopes use _ _ to scan an object _ _ _ and assemble, by _ , the pixel info onto one image, which is displayed on the _ _
laser light; point by point; computer; computer screen
47
what types of dyes are used in laser scanning microscopes?
fluorescent
48
what is 'fluorescence'?
the absorption and re-radiation of light
49
what does fluorescence indicate?
that a protein is being made
50
in laser scanning microscopes _ of a _ _ and lower energy is _ and used to produce a magnified image
light; longer wavelength; emitted
51
why can laser scanning microscopy be used for medical purposes?
it is non-invasive
52
can laser scanning microscopy be used to observe living specimen?
yes
53
what is the maximum magnification of laser scanning microscopes?
x1500-2000
54
what is the maximum resolving power of laser scanning microscopes?
200nm
55
what is the focussing method of laser scanning microscopes?
glass lenses / mirrors + confocal aperture
56
in laser scanning microscopes, energy is _
reflected/emitted
57
what type of image is obtained from laser scanning microscopes?
colour, 3D, low res
58
what are the advantages of using laser scanning microscopes?
100% focusses
laser can be focused at very specific depth - no blurring
images can be taken at successive depths - computer can construct detailed 3D image
can be used to view living things
helps understand relationship between cells
59
what are the disadvantages of using laser scanning microscopes?
low res compared to EMs
only see fluorescent objects - no other structures visible
fluorescence can cause artefacts
60
what is used to illuminate the specimen in electron microscopes?
a beam of electrons with a wavelength of less that 1nm
61
why can more detail of cell ultrastructure be seen with electron microscopes?
electrons have much smaller wavelengths than light waves
62
what must the inside of an electron microscope be to ensure the beams travel in straight lines?
a vacuum
63
what does specimen prep for both TEMs and SEMs involve?
fixation using chemicals/freezing; staining with heavy metals; dehydration with solvents
64
what additional prep steps are required for TEMs?
specimen set in resin and re-stained
65
what additional prep steps are required for SEMs?
specimen fractured to expose the inside and then coated with heavy metals
66
what can you view with TEMs?
very thin cross-sections of an object
67
what is the max magnification of TEMs?
x5,000,000
68
what is the resolving power of TEMs?
0.5nm
69
what focussing method do TEMs use?
electromagnets
70
in TEMs, energy is _
transmitted
71
give examples of stains used for TEMs
lead / uranium / (metal salts)
72
what type of image is obtained from TEMs?
black/white, 2D, high res
73
what are the advantages of using TEMs?
able to view internal structure of objects
view objects at very high resolution
able to view relationships between structures at high resolution
74
what are the disadvantages of using TEMs?
cannot view living material due to staining and preparation
costly to run
inaccessible
only usable in a controlled environment
75
what can you view with SEMs?
the surface of objects at high resolution
76
what is the max magnification of SEMs?
x500,000-3,000,000
77
what is the resolving power of SEMs?
3-10nm
78
what is the focussing method used in SEMs?
electromagnets
79
in SEMs, energy is _
reflected/emitted
80
give examples of stains used in SEMs
gold / platinum / (metal salts)
81
what type of image is obtained with SEMs?
black/white, 3D, high res
82
what are the advantages of using SEMs?
able to view the surface of objects
allows us to see objects in 3D
very high resolution images
83
what are the disadvantages of using SEMs?
resolution not as high as TEMs
costly to run
inaccessible
cannot study living material due to staining and prep
only usable in a controlled environment
84
what is the magnification formula?
magnification = image size / actual size
85
what is a scale bar?
a way of representing the magnification of an image
e.g. a 10mm line = 1km actual size
86
what is magnification?
how many times larger an image is than the real object
87
what is resolution?
the ability to see individual objects as separate entities
88
what is resolution limited by?
the diffraction of light as it passes through samples (and lenses)
this causes individual structures to overlap, so they are no longer seen as separate entities
89
what is diffraction?
the tendency of light waves to spread as thy pass close to physical structures
90
how can resolution be increased?
by using beams of electrons, which have a much shorter wavelength than light
91
why does the use of electron beams, rather than light waves, increase resolution of an image?
much shorter wavelength
individual beams able to be much closer before they overlap
so objects which are much smaller and closer together can be seen separately without diffraction blurring the image
92
1000nm = ?µm
1µm
93
1000µm = ?mm
1mm
94
1000mm = ?m
1m
95
what is an eyepiece graticule?
a glass disc marked with a fine scale of 1 to 100, it has no units
96
does the relative size of the divisions between graticule marks increase or decrease with each increase in magnification?
increase
97
what is used to calibrate the scale on the graticule at each magnification?
using a stage micrometer
98
what is a stage micrometer
a microscope slide with a very accurate scale in micrometres engraved on it
99
what equation is used to calculate the size of 1 graticule division?
1 division = number of micrometres / number of graticule divisions
100
what is the difference between magnification and resolution?
magnification is the amount that an image is scaled up when viewed through a microscope whereas resolution is the ability to resolve or tell apart two very close points in clear detail.
101
what two parts of the microscope is used to magnify the specimen?
the objective lens and the eyepiece lens
102
what is an artefact?
a visible structural detail caused by processing the specimen and not a feature of the specimen
103
explain why staining is used in microscopy
provides contrast between different structures/organelles in the cell as they all absorb stain differently
this allows them to be identified
104
explain the difference between contrast and resolution
contrast is the difference in colour/shade between two objects whereas resolution is the smallest distance between two objects that can still be seen as separate
105
explain why eyepiece graticules do not have units
it is an arbitrary scale which must be calculated for each lens using a stage micrometer
106
explain why artefacts are more likely to be produced when preparing samples for electron microscopy than for light microscopy
more sample preparation in electron microscopy, so more damage is done to the specimen
this damage results in artefacts
107
membrane-bound organelles
organelles that are made up of or surrounded by membranes
108
what kind of cell has only non membrane-bound organelles?
prokaryotic cells
109
describe the nucleus
large organelle
containing chromatin
has a nucleolus
surrounded by a double membrane (nuclear envelope)
nuclear envelope has holes called nuclear pores
110
describe the nuclear envelope
the double membrane surrounding the nucleus of cells
covered in nuclear pores which are big enough for relatively big molecules to pass through
111
describe the function of the nucleus
controls activity of cell
contains most of the cell's DNA - chromosomes/chromatin
112
describe the nucleolus
dense, spherical, dark staining region of the nucleus
113
describe the function of the nucleolus
makes RNA and ribosomes
114
describe the ribosomes
made of rRNA and protein
small and large subunit
115
what size are the ribosomes in eukaryotic cells
large 80S ribosomes - 22nm
116
what size are the ribosomes in the eukaryotic cells
small 70S ribosomes - 18nm
117
describe the function of ribosomes
site of protein synthesis - translation
118
describe the rough endoplasmic reticulum
series of folded, membrane-bound sacs, studded with ribosomes
119
describe the function of rough endoplasmic reticulum
transport of proteins made by attached ribosomes
120
describe the smooth endoplasmic reticulum
a series of tubular membrane-bound sacs, with no ribosomes attached
121
describe the function of smooth endoplasmic reticulum
synthesis of lipids and carbohydrates
122
describe the vesicles
small membrane-bound, fluid filled sac
123
describe the function of vesicles
transport vesicles - move molecules between organelles
golgi vesicles - move molecules from the golgi apparatus to the plasma membrane for exocytosis
secretory vesicles - fuse with the plasma membrane and release their contents outside of the boundaries of the cell
124
describe a lysosome
a specialised vesicle containing digestive enzymes
125
describe the function of a lysosome
used to digest invading microorganisms or old and worn out organelles
126
describe the golgi apparatus
a stack of membrane-bound, flattened sacs
127
describe the function of the golgi apparatus
processes proteins and 'packages' them into vesicles/lysosomes
makes lysosomes
128
describe the mitochondria
spherical/sausage-shaped organelle, surrounded by a double membrane
inner membrane folded to form cristae
central area within inner membrane is called the matrix
129
describe the function of the mitochondria
the site of aerobic respiration, which produces ATP
130
describe a chloroplast
found in plant cells/some protists
double membrane
inner membrane is continuous and folded into sacs called thylakoids, joined by intergranal membrane - containing chlorophyll
131
describe the grana
stacks of thylakoids, joined together by intergranal lamellae
132
describe the cell surface/plasma membrane
membrane found on the surface of animal cells and inside the cell wall of plants, fungi and prokaryotes
133
describe the function of cell surface/plasma membrane
regulates movement of substances in and out of the cell - partially permeable
receptors to allow cell signalling
134
describe the centrioles
small tubes made of microtubules in a 9x3 arrangement, found in pairs near the nucleus of animal cells
135
describe the function of centrioles
involved in formation of spindle fibres to move chromosomes during mitosis/meiosis
136
describe the cilia
small (<10μm long), hair-like projections from the plasma membrane of some animal cells
membrane surrounding a 9+2 arrangement of microtubules
basal body has the same microtubule arrangement as a centriole (9x3)
137
describe the function of the cilia
microtubules allow cilia to move
used in animals to move mucus or waft ova along the oviduct
used by single celled organisms for movement
138
describe the eukaryotic undulipodia (flagella)
in some eukaryotic cells
structurally same as cilia, but longer
cells only have one or two each
139
describe the flagella
look same as eukaryotic undulipodia, different internal structure
long spiral of protein, flagellin, attached to a protein disc at the base
disc rotates, spinning the flagellum - whip like
140
describe the function of the eukaryotic undulipodia/flagella
used in cell movement
141
describe the cellulose cell wall
rigid structure that surrounds plant, fungal and prokaryotic cells
142
what are plant cell walls made of?
cellulose
143
what are fungi cell walls made of?
chitin
144
describe the plant cell vacuole
large, permanent vacuole that is surrounded by the vacuole membrane (tonoplast)
145
what is the function of the permanent vacuole?
contains cell sap
involved in maintaining turgor pressure of the cell
146
what is the name of the membrane surrounding the vacuole?
tonoplast
147
what does cell sap contain?
sugars, amino acids, waste substances
148
what organelles are found in animal cells that aren't in plant cells?
centrioles
lysosomes (maybe)
149
what organelles are found in plant cells that aren't in animal cells?
cellulose cell wall
chloroplasts
permanent vacuole
(middle lamella + plasmodesmata)
150
prokaryotes do not have _ _ organelles
membrane-bound
151
what are prokaryote cell walls made of?
peptidoglycan
152
what are the structures of mitochondria?
inner membrane (cristae)
outer membrane
matrix
inter-membrane space
(mt)DNA
ribosomes
153
what are the structures of chloroplasts?
outer membrane
inner membrane
intergranal lamella
grana
stroma
starch grains
ribosomes
thylakoid discs
thylakoid space
154
what are grana?
stacks of thylakoid discs
155
what occurs in the thylakoid discs, and what do they make?
early stages of photosynthesis, traps light and makes ATP
156
what separates the two membranes of the double phospholipid bilayer membrane in chloroplasts?
the inter membrane space
157
the inner membrane of mitochondria is folded into _
cristae
158
what do the cristae in mitochondria provide?
a large surface area for the reactions in aerobic respiration
159
what is the area between the two membranes of mitochondria? (name and description)
inter membrane space - fluid filled space
160
what is the matrix?
the fluid-filled space in the middle of mitochondria, containing enzymes used in respiration
161
what is the name of the large protein complexes found in the cristae of mitochondria?
stalked particles
162
what are stalked particles?
enzymes contained in cristae of mitochondria
they are used to make ATP for ADP and a phosphate group
163
almost all cell activities are driven by energy released from _
ATP
164
what are thylakoid discs?
flattened sacs - folded sections of thylakoid membrane
165
where are chlorophyll molecules found in chloroplasts?
on thylakoid membranes and intergranal lamellae
166
how are granum connected?
one granum connected to another by intergranal lamellae
167
where do the early stages of photosynthesis occur, and what happens?
in the thylakoid discs, which trap the light and make ATP
168
what do enzymes in the stroma of chloroplasts do?
they use ATP made in the thylakoid discs to make sugar from "fixed" carbon dioxide
169
what are the three main structures of the cytoskeleton?
microtubule
microfilament
intermediate filament
170
what is the diameter of microtubules?
25nm
171
what are microtubules made of?
a tube of tubulin protein subunits
172
what is the function of microtubules?
form eukaryotic cilia and flagella
form tracks for movement of vesicles
form spindle fibres for movement of chromosomes in cell division
form a scaffold, providing structure/mechanical strength to the cell
173
what is the diameter of microfilaments?
7nm
174
what are microfilaments made of?
helical strands of actin subunits
175
what is the function of microfilaments?
cause cell movement/changes cell shape
involved in cytokinesis
lengthen and shorten ('treadmilling')
176
what is the diameter of intermediate filaments?
8-10nm
177
what are intermediate filaments made of?
many different types of protein in a variety of deformable filaments
178
what is the function of intermediate filaments?
form the scaffold inside the cell - provide mechanical strength
179
describe the steps for the exocytosis of proteins in cells
ribosome assembles required protein, which is pinched of into a transport vesicle and moved to the golgi body
the protein is then modified and placed in a secretory vesicle
the protein in the secretory vesicle is transported to the plasma membrane
the secretory vesicle fuses with the plasma membrane, releasing the protein by exocytosis
180
what is a gene?
a length of DNA that codes for one protein
181
what is the name of the chemical found in the nucleus that holds the cell's instructions?
DNA
182
what is the dense spherical region in a nucleus?
nucleolus
183
what is the name of the double membrane surrounding the nucleus?
the nuclear envelope
184
what is the name of the holes found on the nuclear envelope?
nuclear pores
185
what organelle is the site of translation, and where are they found?
ribosomes
free in the cytoplasm / attached to RER
186
what are the 2 types of ER and how are they structurally different?
rough ER - studded with ribosomes / folded, membrane bound sacs
smooth ER - tubular membrane-bound sacs / no ribosomes
187
what are the functions of the two types of ER?
RER - transport of proteins made by attached ribosomes, packages them into transport vesicles
SER - synthesis of lipids and carbohydrates
188
in what type of cell might you find lots of RER?
a cell making lots of proteins
189
what are the sacs, tubes and discs of membrane in the ER and golgi body called?
cisternae
190
where does the golgi body receive vesicles from, and what do the vesicles contain?
receives transport vesicles from the RER, containing proteins
191
what does the golgi body do with the substrates it receives?
modifies them by adding non-protein parts to proteins and packages them into golgi/secretory vesicles
192
where are lysosomes produced?
golgi apparatus
193
what is contained in a lysosome?
digestive enzymes
194
state two roles of lysosomes
digest invading microorganisms
break down old/worn out organelles
195
what structures do plant cells ave that animals cells wouldn’t?
permanent vacuole (+tonoplast)
chloroplasts
cellulose cell wall
plasmodesmata
196
what do animal cells have that plant cells do not?
centrioles / (possibly) lysosomes
197
prokaryotic cells do not contain any _-_ organelles
membrane-bound
198
what are the two major components that make the cytoskeleton?
actin microfilaments / microtubules
199
state three roles of the cytoskeleton within cells
attachment site for organelles
forms centrioles/spindle fibres used for mitosis/meiosis
determines cell shape
cell organelle movement
200
how are vesicles moved around the cell?
motor proteins along microtubule tracks
201
in which type of eukaryotic cell will you not find centrioles?
plant
202
what is the structure of a centriole?
9x3 formation; cylinder made of microtubules; found in orthogonal pairs
203
what is the role of a centrioles?
used in formation of spindles that move chromosomes in cell division
forms basal body of cilia and animal flagella
204
what is the structure of cilium, and where would you find them in humans?
microtubules in 9+2 formation; base of cilium = centriole (9x3)
found as finger like projections in plasma membrane; in trachea / sensory organs
205
what are the key differences between animal and bacterial flagella?
animal - tail like / used for movement / moves side to side / same as cilia, but longer
bacterial - thinner / whip-like / no 9+2 arrangement / rotates / attached to membrane of cell by a hook section, rotated by a molecular motor
206
what size of ribosomes is found in prokaryotic cells?
18nm / 70s
207
where is DNA found in prokaryotic cells?
singular circular chromosome of naked DNA, found in the nucleoid
small, additional loops, called plasmids
208
what are prokaryotic cell walls made of?
peptidoglycan
209
what size are prokaryotic cells?
0.5-5µm
210
what is the only membrane that prokaryotic cells have?
plasma membrane
211
how do prokaryotic and eukaryotic ribosomes differ?
prokaryotic are smaller = 18-20nm / 70s
eukaryotic are larger = 22nm / 80s
212
what is the approximated size of a eukaryote?
5-250µm
213
what is the approximate size of a prokaryote?
0.1-10µm
214
what is the function of pili, and which type of cell are they found in?
enable transfer of plasmids between bacteria (conjugation)
prokaryotic
215
what is the function off the capsule, and which type of cell does it surround?
protective polysaccharide layer
prokaryotic
216
what is the function of plasmids, and which type of cell are they found in?
small, circular lengths of DNA
prokaryotic
217
how do prokaryotic cells divide?
by binary fission, a form of asexual reproduction
218
what is the function of a starch grain within cells?
storage of carbohydrate
219
when were cells first named?
1665
220
list the organelles used in protein synthesis/exocytosis in order of stages
nucleus
ribosomes (on RER)
RER
golgi apparatus
cell membrane
221
what is the name given to the structures which penetrate the walls of adjacent plant cells?
plasmodesmata
222
what type of organelles are only found in eukaryotic cells?
membrane-bound organelles
