Microscopes Flashcards
What is the wavelength of light?
400-700nm
What is the wavelength of a TEM and SEM?
0.005nm
Describe the specimen in a light microscope
Living / non-living on slide
Describe the specimen in a TEM
Non-living
Copper grid
Vacuum
Describe the specimen in a SEM
Non-living
Metal disc
Vacuum
What is the maximum resolution of a light microscope?
200nm
What is the maximum resolution of a TEM?
0.5nm
What is the maximum resolution of a SEM?
3-10nm
What is the maximum magnification of a light microscope?
X 1500
What is the maximum magnification of a TEM?
At least X 500,000
What is the maximum magnification of a SEM?
X 100,000
What is the type of image displayed from a light microscope?
2D colour
What is the type of image displayed from a TEM?
2D black and white
What is the type of image displayed from a SEM?
3D black and white
Colour can be added on a computer
Stains for a light microscope
Coloured dyes
Stains for TEM
Heavy metals
Stains for SEM
Carbon or gold
How is a laser scanning confocal microscope used?
- Fluorescent dye added to cell/specimen/organelle
- Laser beam (light) focused on part of the cell
- Light fluoresces from objects at different depths within cell
- A pinhole sits down in front of the detector
- Eliminates the out of focus light (comes from different depths within cell)
What is the function of a stage micrometer?
To calibrate an eyepiece graticule so that it can be used to make measurements
How is an eyepiece graticule calibrated?
- Align eyepiece graticule and stage micrometer
- Count how many divisions on eyepiece graticule correspond to a set number of stage micrometer divisions
- Calculate how big one eyepiece division is (find out how long every small division is on stage micrometer)
- Calculate the length of one division of the eyepiece graticule
Outline the procedure of preparing a slide
- Stain the sample with an appropriate dye
- Mount the sample on the slide
- Place a cover slip carefully on the slide, avoiding air bubbles
Why is differential staining used?
- Distinguishes between 2 types of organisms that would otherwise be hard to identify
What is an artefact?
A visible structural detail caused by processing the specimen and not a feature of the specimen, e.g. bubbles under cover slip
What is the function of the nucleus?
Contains coded genetic information (DNA) and controls the metabolic activities of the cell
What is the function of the plasma membrane?
Controls what substances enter and leave the cell
What is the function of the nucleolus?
Produce ribosomes
What is the function of the golgi apparatus?
Modifies and packages proteins
What is the function of the mitochondria?
Site of cellular respiration, producing ATP
What is the function of the cytoplasm?
Jelly-like fluid where chemical reactions happen
What is the function of the cytoskeleton?
- Shape and stability
- Holds organelles in place
- Controls cell movement
- Controls organelle movement
What is the function of the ribosomes?
Responsible for protein synthesis
What is the function of the SER?
Responsible for synthesis and storage of lipids and carbohydrates
What is the function of the RER?
Responsible for synthesis and transport of proteins
What is the function of the centriole?
A component of the cytoskeleton involved in assembly and organisation of spindle fibres during cell division
9+2 arrangement(9 sets of microtubule triplets in pairs)
What protein forms microtubules?
Tubulin
What protein forms microfilaments?
Actin
What organelles do plant cells have that animal cells don’t?
- Vacuole
- Chloroplasts
- Cell wall
What is the function of a vacuole?
Contain cell sap to maintain turgor pressure
What is the function of the chloroplasts?
Contain chlorophyll to absorb light for PHS
What is the function of the cell wall?
Contains cellulose to strengthen and support the cell
Describe the structure of the chloroplasts
- Double membrane
- Stroma - fluid enclosed
- Thylakoids - flattened sacs
- Granum - several thylakoids stacked together
- Lamellae - join grana together
How are prokaryotes different to eukaryotes? (8 points)
Prokaryotes;
- Unicellular
- Nucleus not present
- DNA circular (loop of DNA)
- Has extra DNA called plasmids
- Organelles are non membrane-bound
- Ribosomes are smaller (70s)
- Reproduce through binary fission
- Cell wall made from murein
Describe the production and secretion of proteins (7 points)
1- Nucleus contains the gene for the protein (site of transcription, DNA into mRNA)
2- Protein synthesis translation (mRNA into a.a chain) takes place on ribosomes often on RER
3- Protein transported to golgi in vesicle
4- Golgi modified the protein
5- Protein is packaged into a golgi vesicle
6- Vesicle transported to cell-surface membrane
7- Vesicle fuses to membrane and enzyme leaves cell by exocytosis