Cell structures Flashcards
1
Q
What does TEM stand for?
A
Transmission electron microscope
2
Q
What is the source of image in a TEM?
A
the electrons transmitting through the specimen
3
Q
how is the image focussed in a TEM?
A
electromagnets straightening the electron beam
4
Q
What is the magnification of a TEM?
A
x500,000-x2,000,000
5
Q
What is the resolution of a TEM?
A
0.2-0.5nm
6
Q
Can you view live specimen in a TEM and why?
A
no- specimen are placed in a vacuum
7
Q
Is staining required in a TEM?
A
yes- heavy metal staining is used
8
Q
What are some advantages of TEM?
A
- high resolution
- high magnification
9
Q
What are some disadvantages of TEM?
A
- very expensive
- black and white images
- specimen can be damaged by electron beam
10
Q
What does SEM stand for?
A
scanning electron microscope
11
Q
What is the source of image in an SEM?
A
the electrons reflecting off the sides of the specimen
12
Q
How are SEM microscopes focussed?
A
electromagnets straightening the electron beam
13
Q
What is the magnification of an SEM?
A
x100,000-x500,000
14
Q
What is the resolution of an SEM?
A
3-10nm
15
Q
Can live specimen be used in an SEM and why?
A
no- they are placed in a vacuum
16
Q
Is staining required in an SEM?
A
heavy metal staining is used
17
Q
What are some advantages of SEM?
A
- high resolution
-high magnification - 3D imaging
18
Q
What are some disadvantages of SEM?
A
- expensive
- black and white images
- specimen can be damaged by electron beam
19
Q
What is the source of image in a light microscope?
A
the lamp
20
Q
How is a light microscope focussed?
A
objective lens and eye piece lens
21
Q
What is the magnification of a light microscope?
A
x1500-x2000
22
Q
What is the resolution of a light microscope?
A
200nm/ 0.2um
23
Q
Can you view live specimen in a light microscope and why?
A
yes- they are only placed on a slide and they can be suspended in water
24
Q
Is staining required for a light microscope?
A
no- only if you are viewing cells as their organelles are colourless
25
What are some advantages of light microscopes?
- portable
- cheap
- easy to use
-can view live specimen
26
What are some disadvantages of light microscopes?
- low magnification
- low resolution
27
What is the source of image in a laser scanning confocal?
a laser with high light intensity scans image
28
How is the image focussed in a laser scanning confocal?
eye piece lens and objective lens
29
what is the magnification of a laser scanning confocal?
high
30
what is the resolution of a laser scanning confocal?
very high
31
can you view live specimen in a laser scanning confocal?
yes only a laser of light is used
32
is staining required for laser scanning confocal?
no
33
what are some advantages of a laser scanning confocal?
- 3D images
- non-invasive
- high resolution
- high magnification
34
What are some disadvantages of a laser scanning confocal?
- very expensive
- requires training
35
why should cover slips be added at an angle?
to prevent air bubbles
36
why must samples on a slide be thin?
to let light through so you can see the organelles
37
what are the two main groups of bacteria in gram staining called?
gram positive and gram negative
38
what is the process of gram staining?
1) bacteria is stained with crystal violet
2) all bacteria is stained purple
3) add iodine and stain is fixed due to reaction
4) washed in alcohol
5) gram positive will stain purple and negative will lose stain
6) stained with safranin
7) gram neg will stay red and pos will stay purple
39
why does gram positive stain?
- they have a thick layer of peptidoglycan in their cell walls
40
why does gram negative stain red?
- thinner layer of peptidoglycan
- will not retain violet stain well during the decolouring process
- cell walls are not susceptible to penicillin
40
who made the first microscope and how did they do it?
- Hans and Jensen
- put lenses in a tube
41
who also claimed they invented the first microscope?
Galilei
42
who first observed cells?
Robert Hooke
43
What are proposed theories based on?
current and accepted evidence
44
what is the importance of a microscope?
- allows you to view cells
- many organisms are unicellular so you cant see them without a microscope
- allowed people to discover new organisms and processes
45
why do images tend to have a low contrast in a light microscope?
- cells don't absorb a lot of light
- light is below and you view from above
46
what is the importance of staining?
- increases contrast between components as they take up stains to different degrees
- allows organelles to be visible for identification
47
what is gram staining?
a technique used to differentiate between two large groups of bacteria based on their different cell wall constituents
48
in a wet mount, what should be the same a glass and why?
the refractive index should be the same of that of glass to prevent diffraction
49
what is the definition of magnification?
how many times larger an image is compared to the actual image
50
resolution definition
the smallest distance between two points which can still be distinguished as separate entities
51
what is the equation for the actual size of an image?
actual size = image size/ magnification
52
how is a dry mount specimen prepared?
cut into very thin slices with a sharp blade
53
how is a wet mount specimen prepared?
specimen suspended in water or immersion oil
54
how is a squash slide specimen prepared?
specimen suspended in water or immersion oil and lens tissue is used to gently press down the cover slip
55
how is a smear slide specimen prepared?
edge of slide is used to smear the sample
56
what are some examples of specimens used in dry mounts?
- hair
- insects
- pollen
57
what are some examples of specimens used in squash slides?
soft samples
58
what are some examples of specimens used in wet mounts?
- aquatic samples
- other living organisms
59
what are some examples of specimens used in smear slides?
- blood
- any liquid
60
how does diffraction and wavelength of light affect resolution?
shorter wavelength yield means higher resolution
61
explain why staining is needed in terms of contrast?
staining increases contrast between components as they take up stains at different degrees
62
give some examples of positively charged dye and what is it attracted to?
- crystal violet and methylene blue
- attracted to negatively charged material in cytoplasm
63
give examples of negatively charged dyes and what is it repelled by?
- nigrosin and congo red
- repelled by negatively charged cytosol
64
what is the purpose of fixing (in slide production)?
to preserve specimens (chemicals such as formaldehyde)
65
what is sectioning (in slide preparation)?
specimens are dehydrated with alcohol and placed in a wax block before thinly sliced with a microtome
66
what is the purpose of staining (in slide preparation)
to view different organelles as different stains show different structures
67
what is mounting (in slide preparation)?
specimens are secured to a microscope slide with a cover slip
68
what is differential staining?
staining that helps differentiate between different types of organelles
69
what does CLEAPSS stand for and what do they do?
- Consortium of Local Education Authorities for the Provision of Science Services
- provide support for practical work in schools
70
what is on a student safety sheet?
- identify specific risks
- advice on the measures to be taken to reduce risks
- action to take in emergency
71
why are most slides pre-prepared in schools?
- harmful nature of stains
- long complex process needed to produce high quality sections
72
how does penicillin affect gram positive staining?
it inhibits the peptidoglycan production, making the cells fragile
73
how does penicillin affect gram negative bacteria?
it has peptidoglycan between membranes so the penicillin doesn't work aswell
74
what is the acid fast staining technique used for?
to differentiate species of mycobacteria from other bacteria
75
what dye is used in acid fast staining?
carbolfuchsin dye
76
what is used to carry dye into the cells in acid fast staining?
a lipid solvent
77
how do you calculate the number of eye piece divisions?
number of micrometres/ number of eye piece divisions
77
what is a scale micrometer?
a microscope slide with an accurate scale in um
- 100 divisions= 1mm
- 1 division= 0.01mm= 10um
78
what is an eye piece graticule?
- a glass disc with a scale on it
- inserted into a microscope eyepiece
- the scale remains the same at each magnification
79
how do you convert from um to nm?
x1000
80
how do you convert from mm to um?
x1000
81
how do you convert from cm to mm?
x10
82
what is the function of a vacuole?
- maintain turgor (correct pressure)
- selectively permeable
- plants have a permanent vacuole
83
what is the function of cillia?
- sensory- detect things
- movement
84
what is the function of the flagella?
movement
85
what is the function of the cell wall?
- shape
- rigidity
- strength
86
what is the function of centrioles?
produce spindle fibres for cytoskeleton
87
how thick is the plasma membrane?
7nm
88
what is the function of the chloroplasts?
photosynthesis
88
what is the function of the lysosomes?
- contains digestive enzymes
- breaks down old organelles, bacteria and foreign bodies
88
what is the function of ribosomes?
- proteinsynthesis
89
what is the function of the mitochondria?
aerobic respiration (in the cristae) which produces ATP
90
what is the function of the smooth endoplasmic reticulum (SER)?
synthesis and transports lipids and steroids (lipid synthesis)
90
what is the function of the golgi apparatus?
processes and packages vesicles
90
what is the structure of the nuclear envelope?
- double membrane
- has pores
91
what is the function of the rough endoplasmic reticulum (RER)?
- protein synthesis
- transport of proteins
92
what is the size of a nuclear pore?
120nm
93
what is the function of the nuclear envelope?
contains genetic material in a certain place
94
what is the function of the nucleolus?
makes RNA and ribosomes
95
what is the function of the nucleus?
- contains genetic material (DNA)
- cell division
95
what is the function of a cytoskeleton?
- provides shape for cells without cell walls
- movement of cells e.g cillia and flagella
- formation of spindle fibres that move chromosomes
- keep organelles in place
- move organelles e.g vesicles
95
what is a cytoskeleton?
network of protein fibres
95
where is the cytoskeleton present?
in eukaryotic cells
96
what is the plasma membrane around organelles for?
- separate contents from cytoplasm
- controls what can enter and leave the organelle
- surface for reactions to occur on
- eg mitochondria and chloroplasts
97
what is the plasma membrane around cells for?
- controls what leaves and enters as it is partially permeable
- barriers to certain substances
- keeps contents of cell together
- separates cell contents from the environment
97
what is the process of protein synthesis?
1) instructions in the nucleus are transcribed into mRNA
2) mRNA leaves nucleus via nuclear pores
3) mRNA travels to ribosomes where message is read and translated into proteins
4) vesicles transport protein to golgi
5) protein fuses to golgi
6) golgi processes and packages protein
7) protein in vesicles are budded off
8) vesicles fuse with [plasma membrane
9) protein is released through membrane pores (exocytosis)
97
are organelles membrane bound in prokaryotes and eukaryotes?
prokaryotes- non-membrane bound
eukaryotes- both membrane bound and non membrane bound
98
do prokaryotes and eukaryotes have a nucleus?
prokaryotes- no
eukaryotes- yes
98
what type of DNA does prokaryotes and eukaryotes have?
prokaryotes- circular
eukaryotes- linear
99
what DNA organisation do prokaryotes and eukaryotes have?
prokaryotes- proteins fold and condense DNA
eukaryotes- associated with proteins called histones
99
what is the cell type of prokaryotes and eukaryotes?
prokaryotes- unicellular
eukaryotes- unicellular and multicellular
99
what are prokaryotes and eukaryotes cell walls made of?
prokaryotes- peptidoglycan
eukaryotes- chitin in fungi
- cellulose in plants
- not present in animals
99
is the cytoskeleton present in prokaryotes and eukaryotes?
prokaryotes- present
eukaryotes- present but more complex than prokaryotes
99
do prokaryotes and eukaryotes contain extra chromosomal DNA?
prokaryotes- circular DNA called plasmids
eukaryotes- only present in certain organelles such as chloroplasts and mitochondria
100
what is diffraction?
the tendency of light waves to spread as they pass close to physical structures
101
what does metabolism involve?
the synthesis and the breaking down of molecules
102
what are the three components of the cytoskeleton?
microfilaments, microtubules and intermediate fibres
103
what are microfilaments?
contractile fibres formed from the protein actin
104
what are microtubules?
globular tubulin proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of a cell
105
what are the functions of intermediate fibres?
give mechanical strength to cells and help maintain their integrity
106
what are centrioles composed of?
microtubules
107
what is tonoplast?
the membrane of a vacuole in a plant cell
108
what is safranin dye called in gram staining?
a counterstain
109
what is resolution limited by?
the diffraction of light
110
what is the size of the wavelength of the beam of electrons used in electron microscopy?
1nm
111
what is an artefact and what is it caused by?
a visual structural detail caused by processing the specimen and not a feature of the specimen
112
what type of microscopes do artefacts appear in?
both light and electron microscopes
113
what is an example of an artefact?
the bubbles that get trapped under the cover slip
114
what changes happen to the ultra structure of cells when undergoing prep for electron microscopy?
- loss of continuity in membranes
- distortion in organelles
- empty spaces in the cytoplasm
115
what is the beam splitter in a laser scanning confocal?
a dichroic mirror, which only reflects one wavelength (from the laser) but allows other wavelengths (produced by the sample) to pass through)
116
what is the structure of a prokaryote?
a simple structure with just a single undivided internal area
117
what type of organisms are made up of eukaryotic cells?
animals, plants and fungi
118
what is the structure of a eukaryote cell?
complicated internal structure, containing many membrane bound nucleus and cytoplasm, which contains many membrane bound cellular components
119
what type of permeability is a cellulose cell wall and what does it mean?
freely permeable so substances can pass in and out
120
what do vacuoles contain?
cell sap
121
what type of permeability is a vacuole and what does it mean?
selectively permeable which means that some small molecules can pass through it but others cannot
122
what type of permeability is a vacuole that appears in an animal cell?
small and not permeable
123
when did the first prokaryotic cell appear on earth?
around 3.5 billion years ago
124
what were the early prokaryotes adapted to?
extremes of salinity, pH and temperature
125
what are these early prokaryotes called?
extremophiles
126
where can extremophiles be found today?
in hydrothermal vents and salt lakes
127
what shape is the one chromosome prokaryotes have and why?
`supercoiled to make it more compact
128
what are the genes of the chromosome in a prokaryote grouped in to?
operons
129
what size are ribosomes in prokaryotes and eukaryotes?
prokaryotes- smaller- 70s
eukaryote- larger- 80s
130
what type of reproduction do prokaryotes and eukaryotes do?
prokaryotes- binary fission
eukaryotes- asexual or sexual
131
do prokaryotes and eukaryotes have a cell surface membrane?
they both do
