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biology (2) : foundations in bio > CELL STRUCTURE (2.1.1) > Flashcards

CELL STRUCTURE (2.1.1) Flashcards

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1
Q

how do transmission electron microscopes (TEMs) work?

A

a beam of electrons illuminates the specimen by being transmitted through the specimen and focused to produce an image

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2
Q

describe the preparation of a sample for TEMs

A
  1. fixation using chemicals OR freezing
  2. staining with heavy metals
  3. dehydration and embedding in resin
  4. place in a vacuum to view
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3
Q

what are advantages of TEMs?

A
  1. High resolution images
  2. High magnification
    This allows the infernal structures of cells to be seen
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4
Q

what are disadvantages of TEMs?

A
  1. expensive to buy and operate
  2. large and needs to be installed
  3. complex sample prep
  4. risk of artefacts
  5. black and white images
  6. specimens are dead
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5
Q

what is the maximum magnification for TEMs?

A

over X 1 000 000

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6
Q

what is the maximum resolution for TEMs?

A

0.5nm (0.0005μm)

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7
Q

how do scanning electron microscopes (SEMs) work?

A

a beam of electrons is sent across the surface of a specimen and the reflected electrons are collected.

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8
Q

describe the preparation of a sample for an SEM?

A
  1. fixation using chemicals or freezing
  2. staining with heavy metals
  3. dehydration and embedding in resin
  4. place in a vacuum to view
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9
Q

what are the advantages of an SEM?

A
  1. High resolution images
    This allows the internal structures within cells to be seen.
  2. High magnification images
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10
Q

what are the disadvantages of an SEM?

A
  1. Expensive to buy and operate
  2. Large and needs to be installed
  3. Complex sample preparation
  4. Risk of artefacts
  5. Black and white images
  6. Specimens are dead
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11
Q

what is the maximum magnification for an SEM?

A

over X 500 000

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12
Q

what is the maximum resolution for an SEM?

A

2nm (0.002μm)

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13
Q

how do compound light microscopes work?

A

Light source shines up through the specimen, illuminating the whole field at once.
The objective lens produces a magnified image, which is magnified again by the eyepiece lens.

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14
Q

describe function of plasma membrane

A
  • regulates movement of substances in and out of cell
  • has receptor molecules, responds to chemicals e.g. hormones
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15
Q

describe function/structure of cell wall

A
  • supports plant cells
  • rigid structure
  • mainly made from cellulose (carb)
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16
Q

describe the nucleus

A
  • surrounded by nuclear envelope (double membrane), contains nuclear pores
  • contains chromatin (DNA and protein)
  • contains nucleolus
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17
Q

describe the function of the nucleus

A
  • controls cells activities by controlling transcription of DNA
  • pores allow substances to move in and out of cytoplasm
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18
Q

state role of nucleolus

A
  • makes ribosomes
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19
Q

describe the function of a lysosome

A
  • digest invading cells/ break down worn out components of cell
  • contains digestive hydrolytic enzymes
  • kept separate from cytoplasm by surrounding membrane
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20
Q

describe and state the function of ribosomes

A
  • floats in cytoplasm or attached to rER
  • not membrane-bound
  • site where proteins are made/synthesised
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21
Q

state the function of the rough endoplasmic reticulum (rER)

A
  • surface covered in ribosomes
  • folds and processes proteins (that have been made at the ribosomes)
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22
Q

state the function of the smooth endoplasmic reticulum (sER)

A
  • synthesises and processes lipids
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23
Q

state the function of a vesicle

A
  • sac surrounded by membrane
  • transports substances in and out of cell or across organelles
  • some formed by Golgi apparatus or ER
  • some formed at cell surface
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24
Q

state function of Golgi apparatus

A
  • membrane bound, fluid sacs
  • processes and packages new lipids and proteins
  • makes lysosomes
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25
Q

state function of mitochondrion

A
  • site of aerobic respiration
  • ATP produced
  • more found in active cells
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26
Q

describe the mitochondria

A
  • double membrane
  • inner membrane folded, forming cristae
  • inside is matrix, contains enzymes for respiration
27
Q

describe the chloroplast

A
  • found in plant cells only
  • double membrane
  • thylakoid membranes stacked to form grana
  • grana linked by lamellae
  • lamellae, thin pieces of thylakoid membrane
28
Q

state the function of chloroplasts

A
  • site of photosynthesis
  • some photosynthesis occurs in grana, others in stroma (thick fluid)
29
Q

what is the function of centrioles?

A
  • hollow cylinders, made of micro tubules (tiny protein cylinders)
  • involved with the separation of chromosomes during cell division
  • found in animal cells (SOME plant cells)
30
Q

state function of cillia

A
  • hair-like structures
  • have 9 + 2 formation of microtubules in cross- section
  • microtubules allow cillia to move
  • move substances along cell surface
31
Q

state function of flagellum

A
  • 9 + 2 formation of microtubules (9 pairs, 2 in centre)
  • microtubules contract, propelling cell forward
32
Q

what is the function of vacuoles?

A
  • compartments containing cell sap
  • maintain pressure by pushing cytoplasm against the cell wall
  • this keeps the plant cell turgid, prevents plants from wilting
33
Q

what is the term for the detailed structure of cells visible only with an electron microscope?

A

ultrastructure

34
Q

what organelles are present in a plant cell, but not an animal cell?

A
  • cell wall
  • a vacuole
  • chloroplasts
35
Q

what organelles are found in animal cells, but not plant cells?

A
  • lysosomes
  • centrosomes (a pair of centrioles)
36
Q

what is the cytoskeleton composed of?

A

tiny protein threads arranged as
- microfilaments (strands)
- microtubules (cylinders)

37
Q

state 4 functions of the cytoskeleton

A
  1. support cells organelles, keeps them in position
  2. help strengthen cell/maintain its shape
  3. transport organelles and materials within the cell
  4. proteins within the cytoskeleton also cause the cell to move
38
Q

state 3 EXAMPLES of how the cytoskeleton helps processes

A
  1. movement of chromosomes during cell division (contraction of microtubules)
  2. movement of vesicles around cell (cytoskeletal proteins)
  3. movement cilia and flagella (e.g. sperm propelled by flagella, due to it’s cytoskeletal proteins)
39
Q

describe how organelles work together during protein production

A
  1. proteins are synthesised at either: free ribosomes or ribosomes on the rER
  2. then directed to the rER to be processed (folded etc)
  3. transported to Golgi apparatus to be processed further (addition/trimming of sugar chains)
  4. proteins transported around cell in vesicles to their destination (e.g plasma membrane)
40
Q

state examples of prokaryotic vs eukaryotic cell

A
  • PRO: E. coli bacterium, salmonella bacterium
  • EUK: human liver cell, yeast, amoeba
41
Q

compare the sizes of prokaryotic vs eukaryotic cells

A
  • PRO: x small, <2 μm diameter
  • EUK: larger, 10-100 μm diameter
42
Q

compare the DNA in prokaryotes vs eukaryotes

A
  • PRO: DNA circular, forms plasmids
  • EUK: DNA is linear
43
Q

what effect does the nucleus have on DNA in prokaryotes vs eukaryotes

A
  • PRO: no nucleus present, DNA free in cytoplasm
    EUK: DNA contained within the nucleus
44
Q

compare the cell wall composition within prokaryotes vs eukaryotes

A
  • PRO: cell wall made of a polysaccharide
  • EUK: N/A animal cells, cellulose in plant cells, chitin in fungi
45
Q

compare the organelles within prokaryotes v eukaryotes

A
  • PRO: few, no membrane bound organelles
  • EUK: many organelles, including membrane-bound ones
46
Q

compare the flagella in prokaryotes vs eukaryotes

A
  • PRO: (when present) made from protein, flagellin, arranged in a helix
  • EUK: (when present) made from microtubules, arranged in a 9+2 formation
47
Q

compare the ribosomes in prokaryotes vs eukaryotes

A
  • PRO: small, 20nm or less
  • EUK: larger, over 20nm
48
Q

state the function of a capsule in prokaryotes

A
  • protective slimy layer
  • retains moisture
  • adheres to surfaces
49
Q

state the function o pill in prokaryotes

A
  • hair like structures
  • attach to other bacterial cells
50
Q

what is Methylene blue used for?

A

to stain DNA

51
Q

what is Geisma stain used for?

A
  • to differentiate between blood cells
  • RBCs = red
    WBCs = purple
52
Q

what is H&E staining used for?

A
  • Haemotoxylin dyes RNA + DNA purple (so highlights nucleus, ribosomes)
  • Eosin dyes cytoplasm pink
53
Q

describe how to prepare a dry mount (and give an example)

A
  1. thin slices of specimen, to let light through
  2. using tweezers, place in the middle of a clean slide
  3. add a coverslip
    - used for dry specimens, e.g. hair, pollen
54
Q

describe how to prepare a wet mount (and give an example)

A
  1. pipette a drop of water onto a slide
  2. use tweezers to place tweezers on top of drop
  3. stand coverslip next to droplet, carefully lower to avoid air bubbles
  4. put drop of stain near one edge of the coverslip, place paper towel next to opposite edge to draw stain across specimen
    - used for specimens in liquid (e.g. pond water sample, tiny aquatic organisms)
55
Q

how to use a light microscope

A
  1. clip prepared slide onto stage
  2. select lowest objective lens (lowest magnification)
  3. use coarse adjustment knob to bring stage up below objective lens
  4. look down eyepiece lens, use coarse adjustment knob to bring image into focus
  5. adjust focus using fine adjustment knob
  6. if needed, swap to more powerful objective lens and refocus
56
Q

describe how to use an eyepiece graticule and stage micrometer

A

eyepiece garticule = no units micrometer = accurate scale, units, = 0.1mm
1. line up graticule and micrometer
2. check magnification, observe how many eyepiece divisions = 1 stage division
Ex. 4.5 graticules = 1 stage division
3. work out size of 1 graticule
Ex. 0.1 / 4.5 = 0.02mm
4. if object (at this magnification) is 20 eyepiece divisions, multiply by eyepiece graticule value
Ex. 20 x 0.02 =0.4mm

57
Q

how do laser scanning confocal microscopes work?

A
  • laser moves across specimen, which has been stained with a fluorescent dye
  • the specimen is now illuminated by UV and gives off its own light
  • the emitted light is filtered through a narrow pinhole and onto a detector
  • 3D images can be produced by creating images at different focal planes
58
Q

what are the advantages of a laser scanning confocal microscope?

A
  • simple sample preparation
  • specimens can be living or dead
59
Q

what are the disadvantages of a laser scanning confocal microscope?

A
  • low magnification and resolution compared to electron microscopes
  • expensive to buy
60
Q

what is the maximum magnification for laser scanning confocal microscopes?

A

x2000

61
Q

what is the maximum resolution for laser scanning confocal microscopes?

A

0.2μm (200nm)

62
Q

which type of magnification has the highest resolution

A
  • transmission electron microscopes (TEMs)
  • 0.0005μm (0.5nm)
63
Q

describe the structure and function of plasmodesmata

A
  • small channels that penetrate cell walls of adjacent plant cells
  • allow substances to pass directly from the cytoplasm of one cell to another
64
Q

where are microvilli found and what is their function?

A
  • on epithelial cells in the small intestine
  • increase the surface area, therefore increase the rate of exchange of substances

biology (2) : foundations in bio (5 decks)

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