Cell structure and microscopes Flashcards
how does a TEM work
stained by metal salts
beam of electrons passing through a specimen
darker the picture the more dense structure
What kind of images can you see from a TEM
2D black and white
organelles
how does an SEM work
beams of electrons are knocked off the cell surface
what image do you see from an SEM
3D images
black and white
surface
why do we stain cells
to distinguish between cells/organelles and recognise different cells/organelles
improving contrast
to see them more clearly
resolution and magnification of a light microscope
200x
200nm
magnification and resolution of a TEM
500,000
0.5nm
magnification and resolution of an SEM
100,00 x
10nm
how do you use an eyepiece graticule and stage micrometer to view a specimen
calibrate eye piece graticule by making the divisions align
Outline the functions of the cytoskeleton within a cell (3)
Cell support / stability / scaffold / maintain shape;
Movement of flagella / cilia / undulipodia;
Cytokinesis / change shape of cell / endo / exocytosis;
Holds organelles in place;
Moves vesicles;
Moves chromosomes / mRNA;
Forms spindle / centrioles
glucose + glucose =
maltose
what is the purpose of gram staining
To differentiate between gram positive and gram negative bacteria
What’s the stain and colour for gram positive bacteria
iodine/ crystal violet –> purple/blue
Whats the stain for gram negative bacteria
acetic orcein –> DNA red/pink
eosin –>cytoplasm /pink
Why do specimens have to be thin in microspcopy
to allow light to pass through
What are the advantages of light microscopes
Cheap
Portable
Easy to use - no training
living organisms
What are the disadvantages of light microscopes
low magnification and resolution
What type of staining is needed for electron microscopes
Metallic staining - lead
What can you see with a laser scanning confocal microscope
Depth of a cell
Evaluate the use of laser scanning confocal microscopes
Disadvantages - Lower mag an res then electron
Advantages - living cells , depth
Evaluate the use of electron microscopes
Disadvantages - Expensive ,training , non living organisms
Advantages - high mag and res
What’s the difference between the images seen in TEM and SEM
SEM can have added colour while TEM cant
TEM has a greater mag and res
What do samples have to be in an electron microscope before theyre viewed
dehydration
Whats the purpose of differential staining
Identify different cellular components and cell types
How are acid-fast staining techniques done
Cells are dyed and washed with acid
What does mycobacterium stain via acid-fast technique
Bright red
What stain and colour are bacteria
Methylene blue –> stain bacteria blue
What’s the definition of magnification
Number of times larger the image is in comparison to the object
Define resolution
ability to distinguish between the 2 smallest points
How do you prepare a dry mount
thin specimen with a cover slip on top
How do you prepare a wet mount
place water on a slip then cover with a specimen
Put the cover slip on at an angle to prevent nay air bubbles
place a stain next to it and a paper towel on the other end to soak the stain in
What’s the size of the divisions on a stage micrometre
10 um
0.01 nm
What’s the structure and function of the nuclear envelope
double membrane to protect the cytoplasm from damage
What’s the function of the nucleolus
site of ribosome production –> stained dark
What’s the function of the nuclear pore
allow molecules to move in and out
What’s the structure and function of the RER
flattened membrane bound sacs (cisternae-> synthesis occurs)
covered with ribosomes
transport of proteins
Continuous folds with the nuclear membrane
What’s the structure and function of the SER
fluid filled cavities
no ribosomes
lipid and hormone production
What’s the structure and function of the gogi apparatus
Modifies and packages proteins into vesicles
flattened membrane sacs and has secretory vesicles
What’s the function of the ribosomes
Site of protein synthesis
What’s the structure and function of the mitochondria
Site of ATP production
double membrane - inner (cristae)
surrounded by the matrix
What’s the structure and function of the lysosomes
Spherical sacs surrounded by a membrane
contains digestive enzymes - hydrolyse components and break them down
What’s the structure and function of the chloroplast
Site of photosynthesis
2 separate membranes filled by a fluid space (stroma)
flattened sacs (thykloids - that contain chloroplasts)
inside chloroplasts there are granum which are joined by lamellae
What’s the structure and function of the centrioles
Take part in mitosis to form spindle fibres
Made from microtubules
What’s the structure and function of the cell wall
Provides tensile strength
insoluble
maintains strength
What’s the structure and function of the flagella
Microtubules that contract to make it move
What’s the structure and function of the cilia
Made from protein microtubules that help cilia to move
How are proteins secreted
- mRNA is made in the nucleus which leaves through the nuclear pore
- moves to the ribosomes - where protein synthesis occurs
- gets pinched off into a vesicle and fuses with the Golgi apparatus
4.protein becomes packaged and modified - vesicle travels to the plasma membrane and fuses with it
- released by exocytosis - requires ATP
What are the components of the cytoskeleton and their functions
Microfilaments - change the cell shape
Microtubules - move chromosomes and organelles
Intermediate filaments - whole cell support
Compare the structure of prokaryotes vs eukaryotes
Ribosomes - 80 vs 70
Nucleus vs no nucleus
Membrane bound organelles vs no membrane organelles
Larger vs smaller
Circular DNA vs Liner DNA
Flagella in 9+2 formation vs Flagella in a helix structure
Whats the formula to calculate magnification
I = AM
