Cell structure
)
a )
b c )
Light microscopes: calibrating eyepiece graticules and stage micrometers How to stain a sample
● Light is shone up the base, through the sample, up through the 1. Use a pipette to place a small drop of water onto the centre of the
objective lens into our eye glass slide
● The specimen used has to be thin so light can pass through it 2. Use a pair of forceps (tweezers) to place a thin section of the
● The specimen can be alive but sometimes the light causes heat specimen onto the drop of water.
which can damage the organism 3. The specimen should be thin enough to allow light to pass through.
● Used to look at whole cells and tissues, you cannot see organelle 4. Add a few drops of stain to the specimen.
detail in a light microscope ● W hen viewing a specimen you can use an eyepiece graticule to 5. Slowly add a cover slip on the specimen
measure its width and length
Electron microscopes: ry mounts- the specimen is placed directly onto the slide and covered
D
● Eyepiece graticule is a small scale placed within the eyepiece
● Use electrons to form an image with a cover slip
● Since electrons have a shorter wavelength than light, they have a ● The scale divisions will represent different real world distances
depending on the magnification of the objective lens. This means c) staining:
better resolution than light microscopes
Coloured staining binds to chemicals on or in the specimen which allows
● However, they’re more expensive than light microscopes and only the graticule must be calibrated for each objective lens
the specimen to become visible, to see certain organelles and it improves
produce black and white images (computers can add colour to ● A stage micrometre is used to calibrate the graticule contrast
these images) ● Stage micrometre is a glass slide with a scale measured in Some stains bind to specific cell structures - eosin stains cytoplasm pink
● These microscopes require complex preparation of specimens so micrometres and sudan stains membranes and other lipids black
they are more likely to create artefacts.
Artefacts = visible details that aren't part of the specimen being observed, The graticule is calibrated as follows:
Differential staining is using more than 1 chemical stain
like air bubbles or finger prints . F
1 ix the stage micrometer into place on the stage.
2. Look through the eyepiece to line up the micrometer and the
Transmission electron microscope:
graticule. i)
● They use electromagnets to transmit a beam of electrons through a
3. Count the number of graticule divisions that fit into one micrometer Secretion of proteins (enzymes or hormone)
specimen so you can see details inside the specimen
division. ● Normally to produce a protein such as an enzyme or a protein
● The denser parts absorb more electrons so appear darker in the
image formed 4. Use the formula below to calculate the size of each graticule
1. T he nucleus is producing mRNA which leaves thenucleusthrough
● specimens have to be thin enough to allow the electrons to pass division at that magnification: thenuclear pore
through raticle division = size of 1 micrometer division / number of graticule
G 2. The mRNA will attach to aribosome- the ribosome may be
● The specimen has to be viewed in a vacuum so only non living or
divisions attached to the RER or free in the cytoplasm
dead organisms can be observed
3. The protein is made via protein synthesis in the ribosome
● Used to look at organelle detail
4. The protein is transported via avesicleto thegolgi apparatus
● TEM images can appear differently if the cell/organelle has been Steps for viewing a microscope slide 5. This is where the protein is modified and packaged, for example it
cut along different planes/angles or it's become an artifact so it's 1. Clip the prepared slide onto the stage could be combined with a carbohydrate to form a glycoprotein
been damaged and doesn't look how it's supposed to.
2. Select the objective lens with the lowest power 6. The protein is then packaged into avesicleagain
3. Use the coarse focus to move the stage just below the lens 7. The vesicle is moved to thecell surface membraneof the cell
Scanning electron microscope
4. Look through the eyepiece and use the coarse focus to move the where exocytosis will occur
● Used to look at the cell surface detail or the organelle details
● They scan a beam of electrons across the surface of a specimen - stage until the image is roughly in focus
he mitochondria produces ATP which helps the cytoskeleton contract and
T
the reflected electrons are used to form an image 5. Use the fine focus to make the image clearer move the vesicle from the golgi body to the cell surface membrane to allow
● They produce 3D images 6. Is a higher magnification is needed swap the objective lens and exocytosis to occur.
● Similarly to TEMs, they can only view non living or dead specimens refocus
but SEMs can be used on thicker specimens
)
d e) and f) k) the difference between eukaryotic and prokaryotic cells
biological drawings
agnification = the number of times larger the image is in comparison to
M ● E ukaryotic cells have membrane bound organelles and a distinct
Biological drawings should not: the object nucleus whereas prokaryotes don’t.
● Include shading or colouring Resolution = the ability to distinguish between very small structures that ● Ribosomes in a eukaryotic cell is 80s whereas in prokaryotes its
● Include arrow heads for labels are close together, in detail 70s
● Include overlapping lies ● Eukaryotic organisms have linear DNA whereas prokaryotic
Biological drawings should: Magnification = image size/actual size organisms have circular DNA
● Include a title ● The cell wall in eukaryotes is made of cellulose and in prokaryotes
● State the magnification / scale ight microscope:
L its made of murein/ peptidoglycan
● Be drawn with a sharp pencil Resolution = 0.2 micrometers Magnification = x 1,500 Difference between animal and plant cells
● Include smooth, continuous lines TEM ● Plant cells have a vacuole, cell walls and chloroplasts but animal
● Include labels Resolution = 0.5 nanometers Magnification = x1,500,000 cells dnt
● Include accurate sizes of observable structures SEM
Resolution = 5 nanometers Magnification = x1,500,000
)
a )
b c )
Light microscopes: calibrating eyepiece graticules and stage micrometers How to stain a sample
● Light is shone up the base, through the sample, up through the 1. Use a pipette to place a small drop of water onto the centre of the
objective lens into our eye glass slide
● The specimen used has to be thin so light can pass through it 2. Use a pair of forceps (tweezers) to place a thin section of the
● The specimen can be alive but sometimes the light causes heat specimen onto the drop of water.
which can damage the organism 3. The specimen should be thin enough to allow light to pass through.
● Used to look at whole cells and tissues, you cannot see organelle 4. Add a few drops of stain to the specimen.
detail in a light microscope ● W hen viewing a specimen you can use an eyepiece graticule to 5. Slowly add a cover slip on the specimen
measure its width and length
Electron microscopes: ry mounts- the specimen is placed directly onto the slide and covered
D
● Eyepiece graticule is a small scale placed within the eyepiece
● Use electrons to form an image with a cover slip
● Since electrons have a shorter wavelength than light, they have a ● The scale divisions will represent different real world distances
depending on the magnification of the objective lens. This means c) staining:
better resolution than light microscopes
Coloured staining binds to chemicals on or in the specimen which allows
● However, they’re more expensive than light microscopes and only the graticule must be calibrated for each objective lens
the specimen to become visible, to see certain organelles and it improves
produce black and white images (computers can add colour to ● A stage micrometre is used to calibrate the graticule contrast
these images) ● Stage micrometre is a glass slide with a scale measured in Some stains bind to specific cell structures - eosin stains cytoplasm pink
● These microscopes require complex preparation of specimens so micrometres and sudan stains membranes and other lipids black
they are more likely to create artefacts.
Artefacts = visible details that aren't part of the specimen being observed, The graticule is calibrated as follows:
Differential staining is using more than 1 chemical stain
like air bubbles or finger prints . F
1 ix the stage micrometer into place on the stage.
2. Look through the eyepiece to line up the micrometer and the
Transmission electron microscope:
graticule. i)
● They use electromagnets to transmit a beam of electrons through a
3. Count the number of graticule divisions that fit into one micrometer Secretion of proteins (enzymes or hormone)
specimen so you can see details inside the specimen
division. ● Normally to produce a protein such as an enzyme or a protein
● The denser parts absorb more electrons so appear darker in the
image formed 4. Use the formula below to calculate the size of each graticule
1. T he nucleus is producing mRNA which leaves thenucleusthrough
● specimens have to be thin enough to allow the electrons to pass division at that magnification: thenuclear pore
through raticle division = size of 1 micrometer division / number of graticule
G 2. The mRNA will attach to aribosome- the ribosome may be
● The specimen has to be viewed in a vacuum so only non living or
divisions attached to the RER or free in the cytoplasm
dead organisms can be observed
3. The protein is made via protein synthesis in the ribosome
● Used to look at organelle detail
4. The protein is transported via avesicleto thegolgi apparatus
● TEM images can appear differently if the cell/organelle has been Steps for viewing a microscope slide 5. This is where the protein is modified and packaged, for example it
cut along different planes/angles or it's become an artifact so it's 1. Clip the prepared slide onto the stage could be combined with a carbohydrate to form a glycoprotein
been damaged and doesn't look how it's supposed to.
2. Select the objective lens with the lowest power 6. The protein is then packaged into avesicleagain
3. Use the coarse focus to move the stage just below the lens 7. The vesicle is moved to thecell surface membraneof the cell
Scanning electron microscope
4. Look through the eyepiece and use the coarse focus to move the where exocytosis will occur
● Used to look at the cell surface detail or the organelle details
● They scan a beam of electrons across the surface of a specimen - stage until the image is roughly in focus
he mitochondria produces ATP which helps the cytoskeleton contract and
T
the reflected electrons are used to form an image 5. Use the fine focus to make the image clearer move the vesicle from the golgi body to the cell surface membrane to allow
● They produce 3D images 6. Is a higher magnification is needed swap the objective lens and exocytosis to occur.
● Similarly to TEMs, they can only view non living or dead specimens refocus
but SEMs can be used on thicker specimens
)
d e) and f) k) the difference between eukaryotic and prokaryotic cells
biological drawings
agnification = the number of times larger the image is in comparison to
M ● E ukaryotic cells have membrane bound organelles and a distinct
Biological drawings should not: the object nucleus whereas prokaryotes don’t.
● Include shading or colouring Resolution = the ability to distinguish between very small structures that ● Ribosomes in a eukaryotic cell is 80s whereas in prokaryotes its
● Include arrow heads for labels are close together, in detail 70s
● Include overlapping lies ● Eukaryotic organisms have linear DNA whereas prokaryotic
Biological drawings should: Magnification = image size/actual size organisms have circular DNA
● Include a title ● The cell wall in eukaryotes is made of cellulose and in prokaryotes
● State the magnification / scale ight microscope:
L its made of murein/ peptidoglycan
● Be drawn with a sharp pencil Resolution = 0.2 micrometers Magnification = x 1,500 Difference between animal and plant cells
● Include smooth, continuous lines TEM ● Plant cells have a vacuole, cell walls and chloroplasts but animal
● Include labels Resolution = 0.5 nanometers Magnification = x1,500,000 cells dnt
● Include accurate sizes of observable structures SEM
Resolution = 5 nanometers Magnification = x1,500,000
