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Biology > 1) Cells and microscopy > Flashcards

1) Cells and microscopy Flashcards

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1
Q

What is the typical magnification of a light microscope?

A

up to 1500x

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2
Q

What is the typical resolution of a light microscope?

A

limit of 200nm

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3
Q

How can resolution be improved?

A

use radiation with a shorter wavelength

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4
Q

Define magnification

A

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

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5
Q

Total magnification = ?

A

eye piece magnification x objective magnification

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6
Q

Magnification = ?

A

size of image / size of object

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7
Q

Define resolution

A

the ability to distinguish between two distinct objects separately and to see detail

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8
Q

1mm = _m?

A

1 x 10^-3

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9
Q

1μm = _m?

A

1 x 10^-6

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10
Q

1nm = _m?

A

1 x 10^-9

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11
Q

Why are stains used?

A

to make different parts of the specimen stand out more clearly as often colourless and almost transparent

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12
Q

What colour does iodine solution turn starch grains?

A

blue-black

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13
Q

Name two stains which can be applied to living cells directly

A

methylene blue

iodine solution

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14
Q

Some specimens need to be fixed with _ or _ to make proteins and nucleic acids insoluble (killing cells)

A

acetic acid

alcohol

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15
Q

Give 4 features of cell theory

A
  • the cell is the basic unit of all life forms (uni/multicellular) and the smallest unit capable of surviving independently
  • metabolic processes take place inside cells
  • new cells are derived from old cells
  • cells possess genetic material passed on from parent to daughter cells
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16
Q

Give the journey of light through a light microscope

A

bulb under stage -> condenser lens -> specimen -> objective lens -> eyepiece lens

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17
Q

Why does a light microscope contains one or more lenses?

A

to focus light into the eye

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18
Q

Give 3 advantages of a light microscope

A
  • observation of a wide range of specimens (inc. living), smear preparations and thin sections of tissue
  • easy to use (no specialist training required) and transport
  • relatively inexpensive
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19
Q

Give 1 disadvantage of a light microscope

A

limited resolution so most internal cellular structures are not visible

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20
Q

Define electron microscope (EM)

A

microscope that uses a beam of e- as its source of radiation to view a magnified image of an object

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21
Q

An electron microscope has a greater _ than a light microscope

A

resolution

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22
Q

Describe how an electron microscope works (3 points)

A
  1. electrons focused onto a fluorescent screen which emits visible light where electrons hit
  2. forms a photomicrograph (visible image on screen)
  3. final images are black, grey and white however, colour can be added by specialist computer programs to produce false-colour electron micrographs
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23
Q

Give 3 features of a transmission electron microscope (TEM)

A
  • thinner specimens (e- less penetrating)
  • heavy metals are used to stain specimens (large +ive nuclei scatter e- so don’t hit fluorescent screen and leave a dark area) so structures that take up stain appear as dark images
  • 2D, black + white image
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24
Q

Give 4 features of a scanning electron microscope (SEM)

A
  • e- don’t pass through specimen, instead are reflected off its surface
  • beam of e- passed back and forth over surface of specimen in regular pattern
  • pattern of reflected e- / scattered e- reflects contours of specimen
  • 3D image produced with computer analysis
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25
Q

Why would a confocal microscope be used?

A

to obtain high resolution images and 3D reconstructions

to produce focused images of thick specimens at various depths using optical sectioning

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26
Q

What can fluorescent markers be used for?

A

the detection of biological objects

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27
Q

Name 5 key parts of an electron microscope

A 
electron source
magnetic condenser
magnetic objective
magnetic projector
fluorescent screen
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28
Q

Give 1 advantage of an electron microscope

A

greater resolving power (0.1nm) with a higher magnification means smaller objects can be seen in more detail

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29
Q

Give 5 disadvantages of an electron microscope

A
  • large + expensive
  • requires trained personnel and specially designed room
  • specimens in near vacuum environment (air molecules absorb e-) so must be dehydrated + dead
  • complex staining process
  • artefacts may occur due to preparation techniques
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30
Q

What does using a preserved form of specimen enable?

A

the specimen can be cut into sections and treated with a variety of stains to reveal different structures within the tissues and cells

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31
Q

Name the 3 stages temporary slide preparation

A

fixation
staining
mounting

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32
Q

What 2 key things does temporary slide preparation require? Why?

A

70% alcohol and thin glass coverslip

to exclude dust and air; to protect high power objective lens of microscope

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33
Q

Name the 3 stages permanent slide preparation

A 
fixation
dehydration
clearing
embedding
sectioning
staining
mounting
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34
Q

What will a specimen be mounted in if the specimen is likely to dry out or a prolonged examination is likely?

A

glycerine

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35
Q

Which type of blood cell can clearly be seen under a microscope?

A

erythrocytes (red blood cells)

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36
Q

Why do white blood cells require staining?

A

to distinguish between the different types by showing differences in the shapes of their nuclei

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37
Q

What do different structures vary in?

A

the type / quantity of stain they take up

38
Q

What is the benefit of the staining process being automated in a laboratory?

A

allows many slides to be prepared at the same time

39
Q

Why may a blood smear be prepared and examined?

A

to observe the appearance of blood for diagnostic tests (identify cells and pathogens present)

40
Q

Name 3 types of section

A

longitudinal
transverse
oblique

41
Q

Name 3 differential stains for plants, their final colours and what type of tissue each are suitable for

A

eosin -> red = cellulose
toluidine -> blue = lignin
or -> purple = cellulose
iodine KI -> blue-black = starch

42
Q

Why is toluidine used for plant vascular tissue?

A

stains lignified cell walls blue and cellulose cell walls purple
to allow xylem vessels to be distinguished

43
Q

Name 2 Romanowsky stains for blood

A

Leishman’s stain

Wright’s stain

44
Q

Give the 5 steps for using Leishman’s stain

A
  1. blood allowed to dry
  2. fixation with methanol
  3. flooded and left for 2 mins
  4. diluted with water and left for 5-7 mins
  5. washed until pale pink to the naked eye
45
Q

When is Wright’s stain used?

A

for differential white blood cell counts when infections suspected

46
Q

Give a brief 1 sentence description of how a blood film / smear is made

A

a sample of blood is spread onto a microscope slide (usually by machine)

47
Q

What happens if a blood smear is too thick?

A

individual cells cannot be seen

48
Q

What happens if a blood smear is too thin?

A

small number of cells may not be representative

49
Q

Give the 5 steps for preparing a blood smear by hand

A
  1. small drop of blood at the end of a sterile, clean and dry microscope slide
  2. spreader (sterile slide) pushed along slide at a 30 degree angle to spread blood
  3. label with patient’s details
  4. dry in air (cells stick to slide)
  5. fixative to apply cells
50
Q

What are the 4 key components of the blood?

A

plasma
red blood cells
white blood cells
platelets

51
Q

What are the 6 components of blood plasma?

A 
water
proteins
glucose
mineral ions
hormones
carbon dioxide
52
Q

What are the 7 key functions of the blood?

A
  • delivery of oxygen and nutrients to tissues
  • removal of waste from tissues
  • immunological protection
  • clotting
  • transport of cell signalling molecules (e.g. hormones)
  • acting as a buffer to regulate body pH (acidity)
  • distribution of heat to regulate core body temperature
53
Q

How should biological drawings be drawn? (4)

A

in pencil
single, clear continuous line
labels and annotations
total magnification used

54
Q

What are the 2 types of leucocytes?

A

granulocytes and agranulocytes

55
Q

What type of blood cell is an example of a granulocyte?

A

neutrophil

56
Q

What 3 types of blood cell are examples of agranulocytes?

A

monocytes
lymphocytes
macrophages

57
Q

What is the function of erythrocytes?

A

deliver oxygen from lungs to the body and carbon dioxide from tissues to lungs

58
Q

Where are erythrocytes developed?

A

in the bone marrow

59
Q

How are erythrocytes developed?

A

from erythropoietic stem cells by erythropoiesis (stimulated by erythropoietin, EPO)

60
Q

How long does the development of erythrocytes take?

A

7 days

61
Q

What are immature erythrocytes called?

A

reticulocytes

62
Q

How can red blood cells be identified?

A

methylene blue stain

63
Q

How long do erythrocytes circulate for?

A

100 - 120 days

64
Q

Give 3 key features of erythrocytes

A
  • contain haemoglobin (binds reversibly with oxygen to form oxyhaemoglobin)
    lacks nucleus and most organelles so…
  • large surface area to volume ratio
  • biconcave (flexible to squeeze through capillaries)
65
Q

What is the diameter of an erythrocyte?

A

6.2 - 8.2 μm

66
Q

What is the width of an erythrocyte at its thickest point?

A

2 - 2.5 μm

67
Q

What two features of an erythrocyte should be included on its biological drawing?

A

cell surface membrane

cytoplasm (stained darker at edges and lighter in centre)

68
Q

What is an alternative name for platelets?

A

thrombocytes

69
Q

What is the function of platelets?

A

contribute to blood clotting and clot formation

70
Q

Where do platelets develop?

A

in bone marrow

71
Q

How long to platelets circulate for?

A

6 - 7 days

72
Q

Give 3 features of platelets

A

biconcave discs of cytoplasm fragments surrounded by a cell surface membrane
no nucleus
appear as dark purple spots when stained

73
Q

What is the diameter of a platelet?

A

2 - 3 μm

74
Q

What is the function of leucocytes?

A

immunological protection

75
Q

Describe granulocytes

A

contain granules (often lysosomes) in their cytoplasm which stain differently

76
Q

Describe agranulocytes

A

absence of granules in cytoplasm

77
Q

Leucocytes are _ in size than erythrocytes but _ abundant

A

larger

less

78
Q

What is the function of neutrophils?

A

defend against fungal / bacterial infection by phagocytosis (engulfing / breaking down bacteria)

79
Q

How long do neutrophils circulate for? Why?

A

5 days

unable to renew lysosomes so die after breaking down a few pathogens

80
Q

Give 1 key feature of a neutrophil

A

multi-lobed nucleus - increases flexibility to be able to leave capillaries by squeezing through fenestrations in the capillary wall

81
Q

What 3 features of an neutrophil should be included on its biological drawing?

A

cytoplasm - stained light blue
cell surface membrane
multi-lobed nucleus - stained deep blue; no. of lobes vary between 2 + 5

82
Q

What are lymphocytes characterised by?

A

large, deeply stained nucleus surrounded by relatively small cytoplasm

83
Q

What are the 2 types of lymphocyte?

A

B and T

84
Q

What is the function of B lymphocytes

A

produce immunoglobins (antibodies)

85
Q

Name the 3 types of T lymphocytes

A

helper T cells
cytotoxic T cells
natural killer cells

86
Q

What is the function of helper T cells?

A

produce cytokines and co-ordinate immune response

87
Q

What is the function of cytotoxic T cells?

A

bind to antigens on virus infected / tumour cells and destroy them

88
Q

What 3 features of an neutrophil should be included on its biological drawing?

A

cell surface membrane
nucleus - circular; stained dark purple; large
cytoplasm - small quantity; pale purple

89
Q

What is the function of monocytes?

A

phagocytosis
leave bloodstream and differentiate into tissue macrophages (remove cell debris and attack microorganisms) found in lungs, lymph nodes and liver

90
Q

Monocytes circulate for a _ time than neutrophils because _?

A

longer

they are able to replace their lysosomes

91
Q

What 3 features of an neutrophil should be included on its biological drawing?

A

cell surface membrane
nucleus - darkly stained; kidney bean shaped
cytoplasm - stained purple

Biology (33 decks)

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