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B2 > Cell structure > Flashcards

Cell structure Flashcards

1
Q

what are microscopes used for

A

to produce magnified images of objects

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2
Q

describe how light microscopes work

A

use visible light beam focused by a glass lense ( 400nm - 700nm) to produce a 2D photomicrograph

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3
Q

what’s the resolution in light microscopes and what are the limitations of this?

A
  • 200nm
  • ribosomes (20nm) aren’t distinguishable
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4
Q

what are the advantages of using light microscope

A
  • cheap
  • easy to use
  • portable
  • able to view living specimens
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5
Q

equation for total magnification

A

total magnification = objective lens magnification x eyepiece lens magnification

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6
Q

describe how laser scanning microscopes (confocal microscopes) work

A

they use lasers to scan images point by point

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7
Q

what are the advantages of using laser scanning microscopes (confocal microscopes)

A
  • high-resolution, high contrast computer image is formed from pixels
  • depth selectivity allows the microscope to view specimens at different depths
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8
Q

what can laser scanning microscopes be used for

A
  • can be used to swiftly diagnose conditions
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9
Q

describe how electron microscopes work

A
  • e- fired from cathode and focused by magnets onto a screen or photographic plate
  • use a beam of electrons with a wavelength 0.004nm to produce much higher resolution images
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10
Q

what is are some disadvantage of electron microscopes?

A
  • samples must be placed in a vacuum so living organisms can’t be viewed
  • large and very expensive
  • need a great deal of skill and training to use
  • metallic salt stains can be hazardous to user
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11
Q

how are specimens prepared in TEMs (transmission electron microscopes)

A

specimen dehydrated and stained

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12
Q

what role do electrons play in TEMs

A

pass through the specimen

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13
Q

what’s the product of TEMs

A

2D black and white micrograph

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14
Q

what’s the magnification and resolution of TEMs

A
  • 2 million x magnification
  • 0.1nm resolution
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15
Q

how are specimens prepared in SEMs ( scanning electron microscopes)

A

specimen coated with metal film

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16
Q

what role do electrons play in SEMs

A

bounce off specimen

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17
Q

what’s the product of SEMs

A

3D image formed, can be enhanced

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18
Q

what’s the magnification and resolution of SEMs

A
  • 15-200,000x magnification
  • 20nm resolution
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19
Q

why are specimens stained

A

make structures in the cell visible and provides contrast

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20
Q

what’s differential staining

A

when different stains bind to specific structures in the cell

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21
Q

steps in specimen preparation

A
  1. dehydration
  2. embedded in wax, preventing distortion
  3. slicing into thin sections
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22
Q

name 3 stains

A
  • acetic orcein
  • eosin
  • iodine in KI
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23
Q

what’s the function of acetic orcein

A

binds DNA, dark red in colour

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24
Q

what’s the function of eosin

A

stains the cytoplasm pink

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25
Q

what’s the function KI stain

A

stains cellulose yellow, starch grains blue-black

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26
Q

what are eyepiece graticules used for

A

to measure object sizes in eyepiece units (epu)

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27
Q

what are stage graticules used for

A

used to calibrate the eyepiece graticule

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28
Q

how do you measure specimen size

A
  1. fit eyepiece (10x) and stage graticules focus with objective lens for a given magnification
  2. work out what length each epu represents. Stage graticule measures in microns
  3. measure object epu and multiply by this value
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29
Q

define magnification

A

the number of times larger an image appears compared to the real specimen

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30
Q

define resolution

A

the ability to distinguish two different points clearly and produce fine detail

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31
Q

why do electrons microscopes have better resolution

A

they use electron beams with smaller wavelengths

32
Q

equation for image size

A

Image size = object size x magnification
I
A x M

33
Q

What’s the difference between organelles in eukaryotic cells and prokaryotic cells

A

membrane bound organelles in eukaryotic cells

34
Q

function of nucleus

A
  • stores chromatin made of DNA and histones
  • contains nucleolus, which makes ribosomes
35
Q

structure of nucleus

A
  • has double membrane and nuclear pores
36
Q

function of ribosomes

A
  • synthesises polypeptides using mRNA
  • free floating or attached to rough ER
37
Q

structure of ribosomes

A
  • are 20nm in diameter
  • made up of two subunits ( 60s and 40s), each containing roughly equal ratios of rRNA and protein
38
Q

function of mitochondria

A
  • site of aerobic respiration
  • found in animal and plant cells
  • produces ATP from ADP + Pi
39
Q

structure of mitochondria

A
  • double membrane, inner membrane highly folded into cristae
  • spherical/rod/branched (2-5um)
40
Q

function of chloroplasts

A
  • site of photosynthesis
  • produces glucose and oxygen
41
Q

where are mitochondria found

A
  • found in animal and plant cells
42
Q

where are chloroplast found

A
  • found in plant and algae cells only
43
Q

structure of chloroplasts

A
  • double membrane, starch grains and DNA loop
  • inner membrane is continuous with stacks of flattened sacks called thylakoid
  • fluid filled matrix - stroma
  • 4 - 10 um in length
44
Q

structure of rough ER

A
  • contains membranes containing fluid-filled cavities called cisternae that provide a large SA for ribosomes to attach
  • continuous with nuclear membrane
45
Q

function of rough ER

A
  • site of protein synthesis and helps move substances around the cell
46
Q

structure of smooth ER

A
  • contains membranes containing fluid filled cavities called cisternae that provide large SA
  • continuous with nuclear membrane
  • has no ribosomes attached to it
47
Q

function of smooth ER

A
  • is a site of carbohydrate and lipid synthesis, storage and transport
48
Q

structure of Golgi apparatus

A
  • has membranes called cisternae
  • secretory vesicles bring materials to and from Golgi apparatus
49
Q

function of Golgi apparatus

A
  • creates lysosomes; vesicles come to and from the Golgi
  • modifies proteins by adding sugar ( to make glyporoteins), lipids (to make lipoproteins).
  • proteins folded into 3D chape
  • packages and transports proteins in vesicles
  • transports, modifies and stores lipids
50
Q

function of lysosomes

A
  • contain hydrolytic enzymes known as lysozymes
  • hydrolyse and break down cells in apoptosis, or phagocytosed bodies
51
Q

structure of lysosomes

A
  • vesicles of membrane
52
Q

what are lysosomes created by

A

Golgi apparatus

53
Q

function of vacuole

A
  • supports the cell when turgid
  • acts as a store of fluid, sugars, amino acids and pigments
54
Q

where are large permanent vacuoles found

A

plant cells

55
Q

structure of vacuole

A

vacuole surrounded by a membrane called the tonoplast, and contains fluid

56
Q

in which cells are cell walls found in

A
  • plants
  • fungi
57
Q

what are plant cell walls made of

A

cellulose

58
Q

what are cell wall in fungi made of

A

chitin

59
Q

what are membranes

A

partially permeable barriers

60
Q

what’s the cytoskeleton

A

a complex network of proteins found throughout the cell

61
Q

what are centrioles

A

bundles of microtubules arranged into two cylinders that are at right angles to each other

62
Q

what’s the cytoskeleton made of

A
  • made of microfilaments (actin), microtubules and intermediate filaments
63
Q

what’s the function of the cytoskeleton

A
  • helps anchor organelles and provide cell shape and provides mechanical strength
  • moves organelles around cell
64
Q

what are centrioles made of

A
  • tubulin subunits, forms spindle fibres
65
Q

function of centrioles

A

spindles move chromosomes in nuclear division via motor proteins

66
Q

what do centrioles form

A

cilia and undulipodia

67
Q

what are cilia, undulipodia and flagellum

A

projections of cell membrane formed from centrioles, and which contain microtubules

68
Q

features of cilia

A
  • multiple protrusions
  • eukaryotic and prokaryotic cells
  • example - ciliated epithelium in airways moves mucus upwards
69
Q

features of undulipodia/ flagellum

A
  • single protrusion
  • called undulipodia in eukaryotes and flagellum in prokaryotes
  • example - bacterial flagellum for motility & undulipodia in human sperm
70
Q

how are proteins synthesised, transported and secreted

A
  1. Transcribed mRNA leaves nucleus via nuclear pores and attaches to ribosomes at the RER
  2. Ribosomes translate mRNA into polypeptide, which enters RER
  3. Vesicles from cisternae take protein to Golgi apparatus
  4. Golgi apparatus modifies and packages protein and release it into vesicle bound for destination, such as exocytosis
71
Q

features of prokaryotic cells

A
  • smaller than eukaryotic cells
  • no membrane bound organelles
  • smaller (70s) ribosomes
72
Q

process by which prokaryotic cells divide

A

binary fission

73
Q

process by which yeast cells divide

A

budding

74
Q

what’s the function of capsule in prokaryotic cells

A

waxy, surrounds cell wall for protection

75
Q

what’s the function of flagella in prokaryotic cells

A

long projections for movement

76
Q

what’s the function of pili in prokaryotic cells

A

small projections for adhesion

B2 (6 decks)

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