2.2 cell structure and microscopes Flashcards
role of the mitochondria?
site of aerobic respiration and energy production for the cell
found in high quantities in areas that need a lot of energy e.g. sperm, muscles
role of centrioles
involved in cell division and separation of chromosomes
role of plasma membrane?
a semi-permeable membrane that keeps integrity of the interior cell and regulates what substances go in/out of the cell
role of lysosomes?
membrane-bound organelles that contain many strong hydrolytic enzymes that digest all kinds of substances including the cell itself
role of ribosomes?
the site of protein synthesis
builds proteins/amino acids and are either free floating or attached to the RER
role of the golgi apparatus
a group of fluid-filled flattened sacks that are responsible for processing/packaging proteins and lipids into vesicles ready to be transported to where they need to be (also make ribosomes and lysosomes)
role of vesicles?
fluid filled sacks that transport substances and fuse to cell membranes to allow transportation of proteins/hormones in and out of the cell
role of the smooth endoplasmic recticulem?
involved in the production of lipids and steroid hormones
role of the rough endoplasmic recticulum?
connects to the nuclear envelope and is involved in the production of proteins
it contains ribosomes and processed proteins
role of the nuclear pores?
pores in the nuclear membrane that regulate what goes in/out of the nucleus e.g. DNA mRNA
role of the nuclear envolope?
the membrane that encloses the nucleus and protects it from damage
role of the nucleolus?
a dense ball of genetic material
role of the cell wall?
a rigid structure made of cellulose that supports plant cells and gives them strength
role of a large vacuole?
large fluid filled sacs containing water or nutrients the cell might need; it also helps maintain turgor by pushing the contents of the cell against the cell wall to keep it rigid
role of chloroplasts?
important plastids containing photosynthetic pigments (chlorophyll) that allow plants to get energy through photosynthesis
role of the cytoskeleton?
a network of protein threads that:
supports organelles by holding them in place and makes sure they keep their shape
strengthens the whole cell and ensures it keeps its shape
can provide intracellular transport
can contract/cause movement within the cell
role of microfilaments?
long, thin, solid fibres formed from the protein actin that’s involved in cell contraction and movement
role of microtubules?
hollow tubes composed of the protein tubulin that form scaffold-like structures and give the cell shape
act as tracks for the movement of organelles
make up the spindle fibres and centrioles used in cell division
role of intermediate fibres?
provides mechanical strength and helps maintain the cells integrity
what’s a prokaryotic cell?
a small, simple cell (0.5-1.0 micrometres) that doesn’t have a nucleus or membrane bound organelles
features of a prokaryotic cell
no membrane bound organelles no nucleus small ribosomes (18 micrometres) cell wall made of peptidoglycan circular DNA in the form of plasmids ATP made in mesosomes
what’s a eukaryotic cell?
a large sophisticated cell (10-100 micrometres) that can have specialised functions
features of a eukaryotic cell
has a nucleus has large ribosomes (22 micrometres) linear DNA has many membrane bound organelles ATP made in the mitochondria make up plants, animals and fungi in plants cell walls are made of cellulose, in fungi they're made of chitin
what’s endosymbiont theory?
the theory that eukaryotic cells have prokaryotic ancestors; a prokaryote “ate” a smaller prokaryote which then evolved to not be digested because both the host and symbiont benefitted
evidence for endosymbiont theory
mitochondria and chloroplasts are a similar size to bacteria
how do you calculate the actual size of an image?
actual size = image size/magnification
definition of magnification?
the degree to which the size of an image is larger in relation to its actual size
definition of resolution?
how clearly you can distinguish between 2 points/objects that are very close together
how does a light microscope work?
light illuminates the specimen in order to see it more clearly
whats the maximum resolution of a light microscope?
0.2 micrometres
what’s the maximum magnification of a light microscope?
x 1,500
advantages of a light microscope?
it’s cheap
produces a coloured image
can use a dead or live specimen
disadvantages of a light microscope?
can’t produce a very detailed image
produces a 2D image
how does a transmission electron microscope work?
electrons are transmitted through the specimen to produce an image
what’s the maximum magnification of a TEM?
x 500 000
what’s the maximum resolution of a TEM?
0.0002 micrometres
advantages of a TEM?
has very good magnification/resolution
doesn’t produce a coloured image but “false” colour can be added after based on electrons absorbed
disadvantages of a TEM?
expensive
produces a 2D image
only dead specimens can be used (in a vaccum)
how does a scanning electron microscope work?
electrons are reflected off the specimen and collected to produce a 3D image
what’s the maximum magnification of a SEM?
x 100 000
what’s the maximum resolution of a SEM?
0.005 micrometres
advantages of a SEM?
has good resolution/magnification
produces a 3D image
disadvantages of a SEM?
expensive
picture has no colour
the specimen has to be dead (in a vacuum coated in metal e.g. gold)
why do we stain specimens?
to allow you to clearly distinguish details more clearly
helps some parts of the specimen absorb more light/electrons than others so there’s more contrast
why do we coat specimens in a heavy metal solution before viewing it in an SEM?
because metal scatters electrons which creates contrast in the image
how do you prepare a dry mount?
solid specimens are sectioned into thin slices to allow light through it so you can see it clearly under a microscope
it’s placed in the center of the slide and a cover slip is placed on top
hair, pollen and dust can be viewed this way
how do you prepare a wet mount?
tiny aquatic organisms can be viewed this way by being suspended in a liquid (water, immersion oil); pipette a small drop of water on the slide and place the specimen on top, then place a cover slip on top by carefully tilting it at an angle until it’s covered
how do you prepare a squash slide?
prepare a wet mount then use a lens tissue to gently press down the cover slip and squash the sample
root tips can be viewed this way
how do you prepare a smear slide?
use the edge of a slide to smear the sample to create a thin, even coating on another slide then place a cover slip on top
blood cells can be viewed this way
what’s laser scanning confocal microscopy?
a technique used for obtaining high resolution images with the ability to observe at different depths
why is it a laser scanning “confocal” microscope?
because the position of the two pinholes means the light waves from the laser follow the same path as the light waves radiated when the sample fluoresces meaning they have the same focal plane
how to LSCM work?
laser beams are used to illuminate a specimen that’s been treated with a fluorescent dye which causes fluorescence (the absorption and re-radiation of light) from these compounds
this light is then filtered through a pinhole aperture (opening) onto a detector that’s hooked up to a computer which generates an image
why’s it better to use a laser instead of light?
a much clearer image is produced because only light radiated very close to the focal plane is detected and out of focus light from other parts of the specimen that would have caused blurring is blocked by the pinhole
advantages of LSCM?
it’s non invasive and can be used to diagnose diseases of the eye and help in the development of new drugs
the internal structures of transparent objects can be seen
images obtained from optical sectioning can be reconstructed with a computer to produce a 3D image of complex objects
