2.1* Flashcards
(183 cards)
1
Q
Name all the parts of a animal cell.
A
Smooth and rough endoplasmic reticulum, lysosome, Ribosomes, Centrioles, Micro tubules, Nucleus, nucleolus, nuclear membrane, Mitochondria, Golgi apparatus, Plasma membrane.
2
Q
Name the parts of a plant cell.
A
Nucleus, tonoplast, cell membrane (plasma), free ribosomes, cell wall (cellulose), SER, RER, chloroplast, mitochondrion, cytosine, Golgi Body, vacuole, nuclear envelope, amyloplast containing starch.
3
Q
Describe the structure of the nucleus.
A
The nucleus is the largest organelle. When stained, it shows darkened patches known as chromatin. It is surrounded by a nuclear envelope. This is a structure made of two membranes with fluid between them. A lot of holes, called nuclear pores, go right through the envelope. These holes are large enough for relatively large molecules to pass through. There is dense, spherical structure, called the nucleolus, inside the nucleus.
4
Q
What is the function of the nucleus?
A
The nucleus houses nearly all of the cells organic material. The chromatin consists of DNA and proteins. It has instructions for making proteins. Some of these proteins regulate the cells activities. When cells divide, chromatin condenses into visible chromosomes. The nucleolus makes RNA and ribosomes. These pass into the cytoplasm and proteins are assembled at them.
5
Q
When a nucleus is stained what are the darkens patches known as?
A
Chromatin
6
Q
What are the holes in the the envelope of a nucleolus called?
A
Nuclear pores.
7
Q
What is the nucleolus?
A
A dark spherical structure inside the nucleus.
8
Q
What does the chromatin consist of inside the nucleus?
A
DNA and proteins
9
Q
What does the nucleolus make?
A
RNA and ribosomes
10
Q
What is the structure of endoplasmic reticulum?
A
ER consists of a series of flattened, membrane-bound sacs called cisternae.
They are continuous with the outer nuclear membrane. Rough endoplasmic reticulum is studded with ribosomes. Smooth endoplasmic reticulum does not have ribosomes.
11
Q
What is the function of rough endoplasmic reticulum?
A
Rough endoplasmic reticulum provides a large surface area for ribosomes which assemble amino acids into proteins. These proteins will actively pass through the membrane into cisternae and are actively transported to the Golgi apparatus. Some of these proteins may be secreted from the cell surface membrane.
12
Q
What is the structure of a Golgi apparatus ?
A
A stack of membrane-bound, flattens sacs.
It looks like a pile of pancakes
13
Q
What is the shape of mitochondria or a singular mitochondrion.
A
They may be spherical, rod shaped or branched. and are 2-5 um long.
14
Q
What is chromatin?
A
Chromatin is genetic material, consisting of DNA wound around histone proteins.
15
Q
What happens to the chromatin in the nucleus when the cell divides
A
The chromatin condenses and coils tightly into chromosomes. These make up nearly all the organisms genome.
16
Q
How do prokaryotic cells divide?
A
Binary fission and not mitosis
17
Q
Describe what happens before division in binary fission.
A
They do not have linear chromosomes, so could not carry out mitosis. However, before they divide, their DNA is copied so that each cell receives the large loop of DNA and smaller plasmids.
18
Q
Do prokaryotes contain membrane-bound organelles?
A
Prokaryotes do not have any membrane bound organelles, but they do have organelles that are not covered by a membrane, such as ribosomes.
19
Q
What are bacteria and micro-organisms?
A
Bacteria are micro-organisms because they are very small. They are also prokaryotes because of their cell structure. However, not all micro-organisms are prokaryotes. Yeast (which is a single celled fungus) and amoebae have eukaryotic cells.
20
Q
Explain a viruses cells.
A
Viruses are microscopic but they do not have cells.
21
Q
What is the job of the nuclear envelope?
A
It separates the contents of the nucleus with the rest of the cell.
22
Q
How does mRNA leave the nucleus?
A
Through the pores.
23
Q
What are 4 purposes of the nucleus?
A
To control the centre of the cell.
Stores the organisms genome.
Transmits genetic information.
Provides the instructions for protein synthesis.
24
Q
What type of system is rough endoplasmic reticulum?
A
It is the Intracellular support system.
25
What is the structure of Smooth endoplasmic reticulum?
There is a system of membranes, containing fluid-filled cavities (cisternae) that are continuous with the nuclear membrane.
There are no ribosomes on its surface.
26
What is the function of smooth endoplasmic reticulum?
SER contains enzymes that catalyse reactions involved with lipid metabolism, such as;
synthesis of cholesterol
synthesis of lipids/phospholipids needed by the cell.
synthesis of steroid hormones.
It is involved with absorption, synthesis and transport of lipids (from the gut).
27
What brings materials to the Golgi apparatus?
Vesicles.
28
How are proteins modified in the Golgi apparatus.
Adding sugar molecules to make glycoproteins.
Adding lipid ,molecules to make lipoproteins.
Being folded into their 3D shape.
29
In the Golgi apparatus what happens after the protein is packaged into a vessel?
It is stored in a cell or
| Moved to the plasma membrane, either to be incorporated into the plasma membrane, or exported outside the cell.
30
What is the structure of a mitochondrion?
They are surrounded by two membranes with a fluid filed space between them. the inner membrane is highly folded into a cristae.
The inner part of a mitochondrion is a fluid filled matrix.
31
What is the function of the mitochondria?
Mitochondria are the site of ATP production during aerobic respiration.
They are self replacing, so more can be made if the cells energy needs increase.
They are abundant in cells where much metabolic activity takes place, for example in liver cells and at synapses between neurons where neurotransmitter is synthesised and released.
32
What is the size and where are chloroplasts found?
They are large organelles 4-10 um long.
| They are found only in plant cells and some in protoctists.
33
What is the structure of a chloroplast?
They are surrounded by a double membrane or envelope.
The inner membrane with stacks of flattened membrane sacks called thylakoids (resembling stacked discs) which contain chlorophyll. Each stack or pile of thylakoids called a granum (plural; grana). The fluid filled matrix is called the stoma.
34
In a chloroplast what is each stack or pile of thylakoids called?
A granum (plural; grana).
35
What do chloroplasts also contain that isn't for photosynthesising.
Loops of DNA and starch grains.
36
What is the purpose of Chloroplasts?
They are the site of photosynthesis.
37
What happens at the first stage of photosynthesis?
Light energy is trapped by the chlorophyll and used to make ATP, occurs in the grana. water is also split to supply hydrogen ions.
38
What happens in the second stage of photosynthesis?
Hydrogen reduces carbon dioxide, using energy from ATP, to make carbohydrates, occurs in the stoma.
39
Where do you find chloroplasts?
Chloroplasts are abundant in leaf cells, particularly the palisade mesophyll layer.
40
What is the structure of the vacuole?
The vacuole is surrounded by membrane called the tonoplast, and contains fluid.
41
What cells contain a vacuole?
Only plant cells have a large permanent vacuoles.
42
How does a vacuole maintain cell stability?
It is filled with water and solutes and maintains cell stability because when full it pushes against the cell wall, making the cell turgid.
43
Why do cells need to be turgid?
If all the plant cells are turgid then this helps to support plant, especially in non woody plants.
44
What does a lysosome contain?
Powerful hydrolytic (digestive) enzymes.
45
Where are lysosomes most abundant?
They are abundant in phagocytic cells such as neutrophils and macrophages (types of white blood cell) that can ingest and digest invading pathogens such as bacteria.
46
What is the structure of a lysosome?
They are small bags, formed by the Golgi apparatus. Each is surrounded by a single membrane.
47
What is the structure of cilia and undulipodia?
These are protrusions from the cell and are surrounded by the cell surface membrane.
Each contains microtubules.
They are formed from centrioles.
48
What is the function of lysosomes?
Lysosomes keep the powerful hydrolytic enzymes separate from the rest of the cell.
Lysosomes can engulf old cell organelles and foreign matter, digest them and return the digested components to the cell for reuse.
49
What is the function of cilia.
The epithelial cells lining the airways each have millions of cilia that beat and move the body of mucus.
Nearly all cell types in the body have one cilium that acts as an antenna. It contains receptors that allows the cell to detect signals about its immediate environment.
50
What is the function of undulipodia?
The only type of human cell to have an undulipodium (a longer cilium) is a spermatozoon. The undulipodium enables the spermatozoon to move.
51
What organelles do not contain membranes.
Ribosomes, centrioles, cytoskeleton, cellulose cell wall.
52
What is the structure of a ribosome?
They are a small spherical organelles, about 20 nm in diameter.
Made of ribosomal RNA.
Made in the nucleolus, as two separate subunits, which pass through the nuclear envelope into the cell and cytoplasm and then combine.
Some remain free in the cytoplasm ans some attach to the endoplasmic reticulum.
53
What is the function of a ribosome?
Ribosomes bound to the exterior or RER are mainly for synthesising proteins that will be exported outside the cell.
Ribosome's that are free in the cytoplasm, either singly or in clusters, are primarily the site of assembly of proteins that will be used inside the cell.
54
What is the structure of centrioles?
The centrioles consist of two bundles of micro-tubules at right angles to each other.
The microtubules are made of tubulin protein subunits, and are arranged to form a cylinder.
55
Before a cell divides, what is the purpose of the necessary organelle?
Before a cell divides, the spindle, made of threads of tubulin, forms from the centrioles.
chromosomes attach to the middle part of the spindle and motor proteins walk along tubulin threads, pulling the chromosomes to opposite ends of the cell.
56
What is a function of centrioles apart from cell division?
Centrioles are involved in the formation of cilia and undulipodia.
Before the cilia form, the centrioles multiply and line up beneath the cell surface membrane.
Microtubules then sprout outwards from each centriole, forming a cilium or undulipodium.
57
Where are centrioles not found?
Centrioles are usually absent from cells of (higher) plants but may be present in some unicellular green algae, such as chlamydomonas.
58
What is the structure of a cycoskeleton?
A network protein structures within the cytoplasm consists of,
Rod-like micro-filaments made of subunits of the protein actin; they are polymers of actin and each micro-filament is about 7 nm in diameter.
Intermediate filaments about 10 nm in diameter
straight, cylindrical microtubules, made of protein subunits called tubulin; about 18-30 nm in diameter.
59
Give some information on cytoskeletal motor proteins.
The cytoskeletal motor proteins, myosins, kinesins and dyneins are molecular motors. The are also enzymes and have a site that binds to and allows hydrolysis of ATP as their energy source.
60
What is the function of the microfilaments in the cytoskeleton?
The protein microfilaments within the cytoplasm give support and mechanical strength, keep the cells shape stable and allow the cell movement.
61
What is the function of microtubules in the cytoskeleton?
Microtubules also provide shape and support to cells, and help substances and organelles to move through the cytoplasm within a cell.
They form a track along which motor proteins (dynein and kinesin) walk and drag organelles from one part of the cell to another.
They form the spindal before the cell divides. These spindal threads enable chromosomes to be moved within the cell.
Microtubules also make up the cilia, undulipodia and centrioles.
62
What is the function of intermediate filaments in a cytoskeleton?
Intermediate filaments are made of a variety of proteins. They anchor the nucleus within the cytoplasm.
Extend between cells in some tissues, between special junctions, enabling cell-cell signalling and allowing cells to adhere to basement membrane, therefore stabilising tissues.
63
What is the structure of a cellulose cell wall.
The cell wall of plants is on the outside of the plasma membrane. Is it made from bundles of cellulose fibres.
64
What is the function of a cellulose cell wall?
Absent from animal cells the cell wall is strong and can prevent plant cells from bursting when turgid.
The cell walls of plant cells,
Provides strength and support, maintains the cells shape, contribute to the strength and support of the whole plant, are permeable and allow solutions (solute and solvent) to pass through.
Fungi have cell walls that contain chitin, not cellulose.
65
In what ways are prokaryotic cells similar to eukaryotic cells?
```
They both contain ,
a plasma membrane
a cytoplasm
ribosome's for assembling amino acids into proteins
DNA and RNA
```
66
What is the size difference between prokaryotic and eukaryotic cells?
Eukaryotic cells are much larger.
67
How does the mechanical strength of prokaryotic and eukaryotic cells compare?
Prokaryotic cells have a much less well-developed cytoskelaton with no centrioles.
68
What is the main difference in the storage of DNA between prokaryotic and eukaryotic cells?
Prokaryotic cells do not have a nucleus.
69
Which collection of organelles do prokaryotic cells not contain?
prokaryotic cells do not contain membrane bound organelles such as mitochondria, endoplasmic reticulum, chloroplasts or the Golgi apparatus.
70
What do cells walls consist of in prokaryotic and eukaryotic cells?
Prokaryotic cells have cell walls made of peptidoglycan whereas eukaryotic cells never have peptidoglycan cell walls.
71
How is DNA stored in prokaryotic cells?
Prokaryotic cells contain naked DNA that is not wound around histone proteins but floats free in the cytoplasm, as a loop (not linear chromosomes)
72
What do prokaryotic cells contain that eukaryotic cells do not?
A protective waxy capsule surrounding their cell wall.
Small loops of DNA called plasmids, as well as the main large loop of DNA.
Flagella - long whip like projections that enable them to move. The structure of these flagella differs from that of eukaryotic undulipodia.
Pili - smaller hair like projections that enable the bacteria to adhere to host cells or to each other, and allow the passage of a plasmid DNA from one cell to another.
73
What is the first step of making and secreting a protein?
The gene that has the coded instructions for a protein such as insulin, housed on chromatin in the nucleus, is transcribed into a length of RNA, called messenger RNA (mRNA).
74
What happens to the copies of mRNA in the process of making and secreting a protein?
Many copies of this mRNA are made and they pass out of the pores in the nuclear envelope to the ribosome's.
75
In the process of of making and secreting a protein what happens at the ribosome's?
At the ribosome's the instructions are translated and insulin molecules are assembled.
76
In the process of of making and secreting a protein where would a protein pass after it has been assembled.
The insulin molecules pass into the cisternae of the rough endoplasmic reticulum and along these hollow sacks.
77
In the process of of making and secreting a protein how do vessels with insulin inside get to the Golgi apparatus?
Vessels with insulin inside are pinched of from the rough endoplasmic reticulum (RER) and pass via microtubles and motor proteins, to the Golgi apparatus.
The vessels fuse with the Golgi apparatus, where the insulin protein molecules may be modified to release.
78
In the process of making and secreting a protein how would insulin move from the Golgi apparatus out of the cell.
Inside vesicles pinched off from the Golgi apparatus, these molecules pass to the plasma membrane.
The vesicles and plasma membrane fuse, and the insulin is released to the outside of the cell.
79
In the process of of making and secreting a protein what is the bulk transport called?
Exocytosis, an active process for which energy is needed.
80
How do prokaryotic cells divide and why?
By binary fission and not by mitosis. They do not have linear chromosomes, so could not carry out mitosis. However, before they divide, their DNA is copied so that each new cell receives the large loop of DNA and any smaller plasmids.
81
What kind of organelles do prokaryotic cells contain?
Prokaryotes (bacteria) do not have any membrane bound organelles, but they do have organelles that are not covered by a membrane, such as ribosome.
82
Are all micro-organisms prokaryotes?
No, Yeast (which is a single-celled fungus) and amoebae have eukaryotic cells.
83
How are bacteria classified?
Bacteria are micro-organisms because they are very small. They are also prokaryotes because of their cell structure.
84
What evidence indicates that eukaryotic cells evolved from prokaryotes?
Molecular and biochemical evidence, as well a fossil records.
85
Describe how eukaryotes evolved from prokaryotes.
1.5-2 billion years ago when some prokaryotic cells with in-folded membranes (for making ATP, or containing chlorophyll) invaded, or were engulfed by, some other prokaryotes, but not digested. As the invaded prokaryotes membrane folded inwards around the invading cell, this produced the double membrane of what are now chloroplasts and mitochondria.
86
What characteristics do both chloroplasts and mitochondria share with prokaryotic cells?
They have small ribosome's, they have loops of DNA, they also contain RNA, they can divide by binary fission.
87
What is the theory as to how eukaryotic cells arose from prokaryotic cells called?
The endosymbiont theory.
88
What is an electron micrograph?
A photograph of an image seen using an electron microscope?
89
What is magnification?
The number of times larger an image appears, compared with the size of an object.
90
What are organelles?
Small structures within cells, each of which has a specific function.
91
What is a photomicrograph?
A photograph of an image seen using an optical microscope.
92
What is resolution?
The clarity of an image; the higher the resolution, the clearer the image.
93
What type of magnification do microscopes produce and what does this mean?
Microscopes produce linear magnification, which means that if a specimen is seen magnified times 100, it appears to be 100 times wider and 100 times longer then it really is.
94
Compare resolution on a microscope to that of another appliance.
Resolution is the ability of an optical instrument to see or produce an image that shows fine detail clearly. You may have a high-resolution television (called 'ultra-high definition' or UHD) and have noticed how clear and sharp the images on its screen are.
95
What did the development of optical (light) microscopes play a key role in and where are they used?
They played a key role in our understanding of the cell structure. They were the first sort to be used, and are still used in schools, colleges, hospitals, and research laboratories.
96
Why were optical (light) microscopes the first sort to be used, and are still used in schools, colleges, hospitals, and research laboratories?
They are;
Relatively cheap, easy to use, portable and able to be used in the field as well as in laboratories, they are able to be used to study whole living specimens.
97
Present day light microscopes look different from ones used in the 17th century, but what do both types rely on?
Lenses to focus a beam of light.
98
What magnification can optical microscopes magnify up to and what are the limitations?
Optical microscopes allow magnification up to times 1500, or in types up to times 2000, which enables us to see clearly some of the larger structures inside cells. However, because their resolution is limited, they cannot magnify any higher while still giving a clear image.
99
What type of light do optical microscopes use?
Optical microscopes use visible light, a part of the electromagnetic spectrum that has a wavelength between 400 and 700 nm.
100
What wavelength of light do optical microscopes use?
The wavelength of visible light ranges from 400 to 700 nm so structures closer together than 200 nm (0.2 um) will appear as one object.
101
What cannot be examined using a light microscope?
Ribosome's are very small, non-membrane-bound, cell organelles of about 20 nm in diameter, and so they cannot be examined using a light microscope.
102
Using a optical microscope;
| How is the lowest objective lens placed placed over the specimen?
By rotating the nose-piece the lowest power objective lens is placed over the specimen.
103
Using a optical microscope;
| Where is the specimen on a slide placed?
On the stage and clipped into place.
104
Using a optical microscope;
| How do you see an image clear and in focus?
Adjust the coarse focus knob, while looking into the eyepiece, until you see the image clear and in focus.
105
Using a optical microscope;
| How do you get optimum light?
Whilst viewing the image adjust the iris diaphragm for optimum light.
106
Using a optical microscope;
| How do you increase the magnification?
Make sure that the object you wish to be view is directly over the hole in the stage. Now rotate the nose-piece and bring the time 10 objective into place over the specimen. Look down the ocular tube and use the fine focus knob to focus the image.
107
How do you work out total magnification?
Total magnification = magnifying power of the objective lens times magnifying power of the eyepiece.
108
What is a photograph of the image seen using an optical lense called?
A photomicrograph
109
Where do modern digital microscopes display?
On screen.
110
What are laser scanning microscopes also called?
Confocal microscopes.
111
How do laser light microscopes display an image on a computer screen?
They use laser light to scan an object point by point and assemble, by computer, the pixel information into one image, displayed on a computer screen.
112
What is the resolution and contrast of a confocal microscope?
The images are high resolution and show high contrast.
113
What else can confocal microscopes do that is useful in the medical profession?
These microscopes have depth selectivity and can focus on structures at different depths within a specimen. such microscopy can therefore be used to clearly observe whole living specimens, as well as cells.
114
What are confocal microscopes used in the medical profession?
They are used to observe fungal filaments within the cornea of the eye of a patient with a fungal corneal infection, in order to give a swift diagnosis and earlier, and therefore more effective treatment.
They are also used in many branches of biological research.
115
What do electron microscopes use and what does this mean?
Electron microscopes use a beam of fast-travelling electrons with a wavelength of about 0.004 nm. This means that they have much greater resolution than optical microscopes and can be used to give clear and highly magnified images.
116
How do electron microscopes work?
The electrons are fired from a cathode and focused, by magnets rather than glass lenses, on to a screen or photographic plate.
117
Does an electron microscope have a better resolution to other microscopes and why?
Fast travelling electrons have a wavelength about 125 000 times smaller than that of the central part of the visible light spectrum. This accounts for an electron microscope's much better resolution compared with an optical microscope.
118
What happens to the specimen with an transmission electron microscope?
The specimen has to be chemically fixed by being dehydrated and stained.
119
What happens to the beam of electrons with a transmission electron microscope?
The beam of electrons passes through the specimen, which is stained with metal salts. Some electrons pass through and are focused on the screen or photographic plate
120
What picture does a transmission electron microscope produce?
The electrons form a 2D black and white (grayscale) image.
121
What is it called when a photograph is taken of the picture produced by a transmission electron microscope?
When photographed this is called an electron micrograph.
122
What magnification does a transmission electron microscope produce?
Transmission electron microscopes can produce a magnification of up to 2 million times, and a new generation is being developed that can magnify up to 50 million times.
123
`When were scanning electron microscopes developed?
They were developed during the 1960s.
124
How do scanning electron microscopes work?
Electrons do not pass through the specimen, which is whole, but the case secondary electrons bounce off the specimen's surface and be focused on to a screen.
125
What magnification and what type of picture do scanning electron microscopes produce?
This gives a 3D image with a magnification from X15 up to X200,000. The image is black and white, but computer software programmes add false colour.
126
What happens to the specimen when using a a scanning electron microscope?
The specimen still has to be placed in a vacuum and is often coated with a fine film of metal.
127
What problems are there with both electron microscopes?
Both are large and very expensive and they need a great deal of skill and training to use.
Specimens, even whole ones for use in SEMs have to be dead, as they are viewed whilst in a vacuum.
The metallic salt stains used for staining specimen's may be potentially harmful for the user.
128
Give some examples of optical instruments.
The eye, and optical and electron microscopes.
129
What is a logarithmic scale? such as one to compare the range of objects seen with and without microscopes.
A scale that goes up in 10 fold increases.
130
What sizes and give some examples of objects that can be seen with an human eye.
1m, 100nm -hens egg, 10nm, 1mm Amoeba, 100um - onion epidermis cell.
131
What sizes and give some examples of objects that can be seen with an light microscope.
1mm -Amoeba, 100um - onion epidermis cell, 10 um - human cheek cell, 1 um - mitochondrion, chloroplast, bacterium, 100 nm - influenza virus.
132
What sizes and give some examples of objects that can be seen with a electron microscope?
1mm -Amoeba, 100um - onion epidermis cell, 10 um - human cheek cell, 1 um - mitochondrion, chloroplast, bacterium, 100 nm - influenza virus, 10 nm - ribosome, protein - 1nm, lipids, 0.1 nm - atom.
133
What can human eyes distinguish between, and what is the limit?
Your eyes can distinguish objects that are about 0.3 -0.5 mm apart. This is the limit of resolution, but it gives you quite good visual acuity for 'everyday' objects.
134
What produces visual acuity (sharpness)
In the retina, at the back of the eye, are photosensitive cells called cones that work in bright light and produce the visual acuity (sharpness).
135
Why do eagles and hawks have better acuity than us?
You have about 200,000 cones per mm2. Eagles and hawks have many more cones in their retinas, around 1 million per mm2, and therefore have greater resolution and visual acuity.
136
What can can a hawk clearly see when hovering 20m high over a roadside grass verge?
It can clearly see an insect scurrying amongst the vegetation.
137
How far away can an eagle spit a rabbit?
2 miles away and, although it is much smaller then you, it's eyes are about the same size as yours.
138
Give the types of specimen you can view on a slide in a optical microscope.
Living organisms such as Paramecium and Amoeba.
Smear preparations of human blood and cheek cells.
Thin sections of animal, plant and fungal tissue, such as bone, muscle, lea, root or fungal hyphae.
139
How do some microscopes produce a clear image without staining?
Some microscopes use light interference, rather than light absorption.
Some use a dark background against which the illuminated specimen shows up.
140
Why do some microscopes use a stain?
Many biological structures, including single-celled organism such as Paramecium, are colourless and transparent.
141
When are light microscopes particular useful?
For studying living specimens.
142
How can you observe living specimens with a school microscopes?
By adjusting the iris diaphragm to reduce the illumination of the specimen.
143
What are stains?
Stains are coloured chemical that bonds to molecules in or on the specimen, making the specimen easy to see.
144
Give an example of a stains.
Methylene blue is an all-purpose stain.
145
What is differential staining?
Some stains are some office to cell structures, staining each structure differently so the structures can be easily identified within a single preparation .
146
What stain stains chromosomes?
Acetic orcein binds to DNA and stains chromosomes dark red.
147
What stains stains lipids?
Sudan red stains lipids.
148
What stain stains the cytoplasm?
Eosin
149
What dies potassium iodide stain?
Iodine in potassium iodide solution stains the cellulose in plant cell walls yellow, and starch granules blue/black (these will look violet under a microscope).
150
How are prepared and permanently fixed slides prepared?
They have been made by experts in the laboratory by,
Dehydrating the specimens
Embedding them in wax to prevent distortion during slicing.
Using a special instrument to make very thin slices called sections - these are stained and mounted in a special chemical to preserve them.
151
On a photomicrograph why can you find the actual size of structures?
Because you know the magnification.
152
How do you find our the actual thickness of a leaf from a photomicrograph?
Measure the widest part of the leaf on the photomicrograph in mm.
Convert that measurement to um by multiplying by 1000.
Now divide this figure by the magnification. This tells you the actual thickness of the leaf at this point.
153
If you are told the actual size of a structure on a photomicrograph (A), and you measure it's image size on the photomicrograph (I), in um [mm x 1000] how can you calculate the magnification factor (M).
M=I/A
| There are no units for magnification but if, for example, the magnification is 1000, them you must write it as x1000.
154
When you observe structures in a microscope section, bear in mind the following:
Cells have a 3D structure and you are looking at a 3D section.
What else should you bear in mind?
( Not too important) Depending on whereabouts in the cells the section was cut, some structures may be absent from your slide section.
Depending how certain structures are orientated in the cell, they will appear as different shapes. For example, mitochondria sliced lengthways (in longitudinal section) would appear sausage shaped, but if sliced transversely (crossways) will appear round and if sliced obliquely ( slanting ) will appear elliptical.
155
You need to be able to make clear, labelled drawings of specimens you examine under a light microscope.
How do you prepare to make a drawing?
Use a prepared slides such as a transverse section through a dicot leaf. Set it up on the microscope. Focus the specimen under low power.
Use a sharp HB pencil.
156
When making a drawing of a slide what writing should you include?
Use a title that explains exactly what the drawing is and the magnification used.
Indicate the scale - i.e. how much bigger your drawing is than the the size of an image.
157
When making a drawing of a slide what is the first step?
Make a low-power plan of the specimen to show where the different tissue areas are, and do not draw any individual cells. Use clear unbroken lines and do not shade any areas.
Label the areas shown on the lower plan.
Always draw what you see, not what you think the specimen should look like from the textbook.
158
When making a drawing of a slide how do you prepare to change to high power?
Indicate on the plan a portion of the tissues that you will include in a high-power drawing.
Make sure that this area of the specimen on the slide is directly over the the hole in the microscope stage.
Turn the nosepiece and bring the bigger objective lens into place over it. Make sure that it fully clicks into place.
159
When making a drawing of a slide, how do you finish the drawing off on high-power.
Use the fine focus knob to bring the specimen into sharp focus.
Make a separate drawing if two or three cells from the region that you highlighted. Draw clear unbroken lines and do not shade.
Label as many structures as you see and identify. Use a ruler to draw the label lines and make sure that each label points exactly to the structure identified.
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What is a eyepiece graticule?
A measuring device. It is placed in the eyepiece of a microscope and acts as a ruler when you view an object under a microscope.
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What is a stage graticule?
A precise measuring device. It is a small scale that is placed on a microscope stage and used to calibrate the value of eyepiece divisions and different magnifications.
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A microscope eyepiece can be fitted with a graticule. What is this graticule?
This graticule is transparent with a small ruler etched onto it.
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How does a graticule work?
As the specimen is viewed, the eyepiece graticule scale is superimposed on it and the dimensions of the specimen can be measured (just as you can measured a large object by placed a ruler against it) in eyepiece units (epu).
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What is the scale of the eyepiece graticule?
An arbitrary scale.
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Why is the scale if the graticule an arbitrary scale?
It represents different lengths at different magnifications. The image of the specimens looks bigger at higher magnifications, but the actual specimen has not increased in size.
166
What has to be done to the eyepiece scale for each objective lens when using a graticule.
The eyepiece scale has to be calibrated (its value worked out) for each different objective lens.
A stage graticule is used only to calibrate the eyepiece graticule.
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What is a stage graticule that is used to calibrate the eyepiece graticule?
A microscopic ruler on a special slide, called a stage graticule, is placed on the microscope stage.
The ruler is 1mm long and divided into 100 divisions. Each division is 0.01 mm or 10 um (micrometers).
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What is the first stage of using a stage graticule to calibrate the eyepiece graticule.
Insert an eyepiece graticule into the x10 eyepiece of your microscope. This ruler has a total of 100 divisions .
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What is the second stage of using a stage graticule to calibrate the eyepiece graticule.
Place a stage graticule on the microscope stage and bring it into focus, using the low power (x4) objective. Total magnification is now x40.
170
When using a stage graticule to calibrate the eyepiece graticule what is the stage after focusing the stage graticule on low power?
Align the eyepiece graticule and the stage graticule. Check the value of one eyepiece division at this magnification on your microscope.
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If the stage graticule is 1mm or 1000 um and corresponds to 40 eyepiece divisions what is each eyepiece division?
1000/40 um = 25 um
172
When using a stage graticule to calibrate the eyepiece graticule what is the stage after using low power on the microscope?
Now use the x10 objective lens on your microscope (total magnification is x100) and focus on the stage graticule.
Align them both.
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On the x10 objective lens if 100 eyepiece division now corresponds with 1 mm or 1000 um what would each eyepiece division be?
1000/100 um = 10um
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If the magnification of the eyepiece lens is x10, the magnification of objective lens is x4 and the total magnification is x40 what is the value of one eyepiece division (epu) (um)
25
175
If the magnification of the eyepiece lens is x10, the magnification of objective lens is x10 and the total magnification is x100 what is the value of one eyepiece division (epu) (um)
10
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If the magnification of the eyepiece lens is x10, the magnification of objective lens is x40 and the total magnification is x400 what is the value of one eyepiece division (epu) (um)
2.5
177
If the magnification of the eyepiece lens is x10, the magnification of objective lens is x100 (oil-immersion lens) and the total magnification is x1000 what is the value of one eyepiece division (epu) (um)
1.0
178
When doing an investigation to observe and measure starch grains (amyloplasts) in potato tuber cells.
What is the first stage?
Using a sharp knife, gently scrape a little material from the surface of a peeler raw potato and place it on to a microscope slide. You need a very thin layer on the slide. In that material will be potato tuber cells
179
When doing an investigation to observe and measure starch grains (amyloplasts) in potato tuber cells.
What is the step after preparing your slide?
Place two drops of iodine/potassium iodide (KI) solution on them and carefully add a coverslip.
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When doing an investigation to observe and measure starch grains (amyloplasts) in potato tuber cells. How do you recognise amyloplasts?
Examine this slide under the microscope. Use low power first and then use high power magnification. The amyloplasts stained with iodine solution will appear violet in colour.
181
When doing an investigation to observe and measure starch grains (amyloplasts) in potato tuber cells.
What do you record?
Measure the length and width of three amyloplasts.
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What is the triangle that may help you use and substitute the equation involving actual size, image size, magnification.
Actual size = image size/magnification
Magnification = image size/actual size
I
AXM
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There is a worked example box on page 34, which you may want to have a go at.
The End :)
