B1.1 Flashcards
What is placed on a slide in a light microscope?
A specimen is placed on a thin piece of glass called a slide.
Why might you need a stain for some specimens?
If the specimen is colourless, a stain is used to identify organelles. Or it is used to highlight different structures or tissues
What is a cover slip and its purpose?
A small piece of glass placed on top of the specimen to protect the lens.
What is the function of the stage and lamp in a light microscope?
The stage holds the slide, and the lamp shines constant light on it so the specimen can be viewed
What do the objective and eyepiece lenses do?
The objective lens magnifies the image, which is further magnified by the eyepiece lens.
Define ‘magnification’.
The degree to which the size of an image is larger than the real object.
What is the formula for object magnification?
Magnification = image size ÷ actual(object) size.
How is the total magnification of a microscope calculated?
Total magnification = magnification of the eyepiece × magnification of the objective lens.
Define ‘resolution’ in microscopy.
The ability to distinguish between two points that are close together.
Why is standard form useful in microscopy?
It helps compare very large or small numbers efficiently.
What is the standard form for 0.000015.
1.5 × 10⁻⁵
What is the standard form for 3400
3.4 × 10³
State three advantages of light microscopes.
1) Relatively cheap
2) Can be used in the field
3) Can look at living specimens
4) does not require specialist training
State three disadvantages of light microscopes
1) Low resolution (~200nm)
2) Limited magnification (up to ×1500)
3) Some organelles require staining
What do electron microscopes use instead of light?
Electrons
Why do electron microscopes offer higher resolution than light microscopes?
Electrons have a much smaller wavelength than light waves.
Name the two types of electron microscopes.
SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope)
What does SEM produce and at what resolution/magnification?
SEM produces 3D images at 10nm resolution, ×100,000 magnification.
What does TEM produce and at what resolution/magnification?
TEM produces 2D images at 0.2nm resolution, ×500,000 magnification.
Give two advantages of electron microscopes.
1) Can see very small organelles
2) SEM can produce 3D images
List four disadvantages of electron microscopes.
1) Cannot view living specimens
2) Extremely expensive
3) Very large and immobile
4) Require specialist training
What is the function of the nucleus?
Contains the genetic material, which codes for a particular protein, and is enclosed in a nuclear membrane.
What is cytoplasm and what does it contain?
Cytoplasm is a liquid substance where chemical reactions occur; it contains enzymes and organelles.
What is the function of the cell membrane?
Contains receptor molecules to identify and selectively control what enters and leaves the cell.
What happens in the mitochondria?
Mitochondria are the site of aerobic respiration, providing energy for the cell.
Where does protein synthesis occur and on what structure?
Protein synthesis occurs in the ribosomes, which are found on the rough endoplasmic reticulum.
Where does photosynthesis take place in plant cells?
In the chloroplasts.
What pigment is found in chloroplasts and what is its function?
Chlorophyll; it harvests light needed for photosynthesis and makes the chloroplast green.
What does the permanent vacuole contain and what is its role?
Contains cell sap, found within the cytoplasm, and improves the cell’s rigidity.
What is the plant cell wall made of, and what does it do?
Made of cellulose and provides strength to the cell.
What is the function of cytoplasm in prokaryotic cells?
Same as in eukaryotic cells — it is where chemical reactions occur and organelles are found
Do prokaryotic cells have a nucleus?
No, they do not have a nucleus.
Where is the genetic material located in prokaryotic cells?
It floats freely in the cytoplasm as a single circular strand of DNA.
What is a plasmid in a bacterial cell?
A plasmid is a small ring of DNA.
What is the bacterial cell wall made of?
Peptidoglycan, which is a different compound from the cellulose found in plant cell walls.
