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Biology > 2.2 cell structure and microscopes > Flashcards

2.2 cell structure and microscopes Flashcards

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1
Q

role of the mitochondria?

A

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

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2
Q

role of centrioles

A

involved in cell division and separation of chromosomes

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3
Q

role of plasma membrane?

A

a semi-permeable membrane that keeps integrity of the interior cell and regulates what substances go in/out of the cell

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4
Q

role of lysosomes?

A

membrane-bound organelles that contain many strong hydrolytic enzymes that digest all kinds of substances including the cell itself

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5
Q

role of ribosomes?

A

the site of protein synthesis

builds proteins/amino acids and are either free floating or attached to the RER

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6
Q

role of the golgi apparatus

A

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)

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7
Q

role of vesicles?

A

fluid filled sacks that transport substances and fuse to cell membranes to allow transportation of proteins/hormones in and out of the cell

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8
Q

role of the smooth endoplasmic recticulem?

A

involved in the production of lipids and steroid hormones

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9
Q

role of the rough endoplasmic recticulum?

A

connects to the nuclear envelope and is involved in the production of proteins
it contains ribosomes and processed proteins

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10
Q

role of the nuclear pores?

A

pores in the nuclear membrane that regulate what goes in/out of the nucleus e.g. DNA mRNA

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11
Q

role of the nuclear envolope?

A

the membrane that encloses the nucleus and protects it from damage

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12
Q

role of the nucleolus?

A

a dense ball of genetic material

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13
Q

role of the cell wall?

A

a rigid structure made of cellulose that supports plant cells and gives them strength

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14
Q

role of a large vacuole?

A

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

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15
Q

role of chloroplasts?

A

important plastids containing photosynthetic pigments (chlorophyll) that allow plants to get energy through photosynthesis

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16
Q

role of the cytoskeleton?

A

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

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17
Q

role of microfilaments?

A

long, thin, solid fibres formed from the protein actin that’s involved in cell contraction and movement

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18
Q

role of microtubules?

A

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

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19
Q

role of intermediate fibres?

A

provides mechanical strength and helps maintain the cells integrity

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20
Q

what’s a prokaryotic cell?

A

a small, simple cell (0.5-1.0 micrometres) that doesn’t have a nucleus or membrane bound organelles

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21
Q

features of a prokaryotic cell

A 
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
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22
Q

what’s a eukaryotic cell?

A

a large sophisticated cell (10-100 micrometres) that can have specialised functions

23
Q

features of a eukaryotic cell

A 
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
24
Q

what’s endosymbiont theory?

A

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

25
Q

evidence for endosymbiont theory

A

mitochondria and chloroplasts are a similar size to bacteria

26
Q

how do you calculate the actual size of an image?

A

actual size = image size/magnification

27
Q

definition of magnification?

A

the degree to which the size of an image is larger in relation to its actual size

28
Q

definition of resolution?

A

how clearly you can distinguish between 2 points/objects that are very close together

29
Q

how does a light microscope work?

A

light illuminates the specimen in order to see it more clearly

30
Q

whats the maximum resolution of a light microscope?

A

0.2 micrometres

31
Q

what’s the maximum magnification of a light microscope?

A

x 1,500

32
Q

advantages of a light microscope?

A

it’s cheap
produces a coloured image
can use a dead or live specimen

33
Q

disadvantages of a light microscope?

A

can’t produce a very detailed image

produces a 2D image

34
Q

how does a transmission electron microscope work?

A

electrons are transmitted through the specimen to produce an image

35
Q

what’s the maximum magnification of a TEM?

A

x 500 000

36
Q

what’s the maximum resolution of a TEM?

A

0.0002 micrometres

37
Q

advantages of a TEM?

A

has very good magnification/resolution

doesn’t produce a coloured image but “false” colour can be added after based on electrons absorbed

38
Q

disadvantages of a TEM?

A

expensive
produces a 2D image
only dead specimens can be used (in a vaccum)

39
Q

how does a scanning electron microscope work?

A

electrons are reflected off the specimen and collected to produce a 3D image

40
Q

what’s the maximum magnification of a SEM?

A

x 100 000

41
Q

what’s the maximum resolution of a SEM?

A

0.005 micrometres

42
Q

advantages of a SEM?

A

has good resolution/magnification

produces a 3D image

43
Q

disadvantages of a SEM?

A

expensive
picture has no colour
the specimen has to be dead (in a vacuum coated in metal e.g. gold)

44
Q

why do we stain specimens?

A

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

45
Q

why do we coat specimens in a heavy metal solution before viewing it in an SEM?

A

because metal scatters electrons which creates contrast in the image

46
Q

how do you prepare a dry mount?

A

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

47
Q

how do you prepare a wet mount?

A

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

48
Q

how do you prepare a squash slide?

A

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

49
Q

how do you prepare a smear slide?

A

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

50
Q

what’s laser scanning confocal microscopy?

A

a technique used for obtaining high resolution images with the ability to observe at different depths

51
Q

why is it a laser scanning “confocal” microscope?

A

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

52
Q

how to LSCM work?

A

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

53
Q

why’s it better to use a laser instead of light?

A

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

54
Q

advantages of LSCM?

A

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

Biology (23 decks)

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