Cell Structure Flashcards
1
Q
what is the definition of magnification?
A
how much bigger the image is than the specimen
2
Q
how do you calculate magnification?
A
magnification = image size ÷ object size
3
Q
how do you convert between units?
A
millimeter (mm) – x1000 –> micrometer (um) – x1000 –> nanometer (nm) – x1000 –> picometer (pm)
4
Q
what is the definition of resolution?
A
how well a microscope can distinguish between two points that are close together
it refers to how much detail can be seen in the image
5
Q
label this microscope
A
6
Q
what is the eye piece graticule?
A
the scale fitted onto the eyepiece of a microscope
it has numbers but no units
7
Q
what is the scale micrometer?
A
a microscope slide with an accurate scale and units
8
Q
what is the scale micrometer used for?
A
to work out the value of divisions on the eye piece graticule at a particular magnitude
9
Q
what are the 4 types of microscope?
A
- light microscope
- laser scanning confocal microscope
- transmission electron microscope (TEM)
- scanning electron microscope (SEM)
10
Q
how does a light microscope work?
A
- light passes from the condenser lens, through the specimen, where certain wavelengths are filtered to produce an image
- the light then passes through the objective lens, which focuses it and can be changed in order to alter the magnification
- finally, the light passes through the eyepiece lens into the eye, which can also be changed to alter the magnification
11
Q
how do you use a light microscope?
A
- clip the slide onto the stage
- select the lowest powered objective lens (the one that produces the lowest magnification)
- use the coarse adjustment knob to move the objective lens to just above the slide
- look down the eyepiece and adjust the focus with the fine adjustment knob until the image is clear
- swap to a higher powered (magnified) objective lens if needed and refocus
12
Q
what is the maximum resolution of a light microscope?
A
0.2um
13
Q
what is the maximum magnification of a light microscope?
A
x1500
14
Q
what are the properties of the image seen through a light microscope?
A
- 2D
- colorless
15
Q
how does a laser scanning confocal microscope work?
A
- a laser beam is focused through a lens which is aimed at a beam splitter
- this splits the beam and some of the light is directed towards the specimen
- when the laser hits the dyes, it causes them to give off fluorescent light, which is focused through a pinhole onto a detector (meaning any out-of-focus light is blocked)
- the detector is hooked up to a computer which generates an image
16
Q
what is a laser scanning confocal microscope used for?
A
to look at different objects at different lengths in thick specimens
17
Q
what are the properties of the image seen through a laser scanning confocal microscope?
A
- 2D
- can be 3D if multiple images are combined together
18
Q
how does a transmission electron microscope work?
A
- a beam of electrons is transmitted through the specimen via a vacuum focused by electromagnets
- denser parts of the specimen absorb more electrons which makes them appear darker on the image
19
Q
what is the maximum resolution of a transmission electron microscope?
A
0.0002um
20
Q
what is the maximum magnification of a transmission electron microscope?
A
x1000000 plus
21
Q
what are transmission electron microscopes used to look at?
A
- very small organelles (as they provide very high resolution images)
- internal structures of organelles in detail
22
Q
what are the properties of the image seen through a transmission electron microscope?
A
- 2D
- black and white
23
Q
what are the disadvantages of a transmission electron microscope?
A
- the specimen used must be quite thinly sliced which may be hard to source
- the angle you cut the specimen can affect how they appear
- cant be done on a living specimen (only dead)
- doesn’t produce colored images
- a lot of preparation is needed to prepare the specimen
24
Q
how does a scanning electron microscope work?
A
- a beam of electrons is beamed across the specimen
- this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
25
what is the maximum resolution of a scanning electron microscope?
0.002um
26
what is the maximum magnification of a scanning electron microscope?
x500000
27
what are scanning electron microscopes used to look at?
the surface of the specimen
28
what are the properties of the image seen through a scanning electron microscope?
- 3D
- black and white
29
what are the disadvantages of a scanning electron microscope?
- gives lower resolution images that the transmission electron microscopes
- cant be done on a living specimen (only dead)
- doesn't produce colored images
- a lot of preparation is needed to prepare the specimen
30
why are electron microscopes better than light microscopes?
- they have a higher resolution so give more detailed images
- this is due to electrons having a much smaller wavelength than light waves
31
how do you mount a dry specimen?
1. cut a thin slice of specimen so that light can pass through
2. using tweezers, pick it up and place it in the center of a clean slide
3. place a cover slip on top
32
what 4 examples that dry mounts used on?
- hairs
- pollen
- parts of insects
- parts of flowers
33
how do you mount a wet specimen?
1. pipette a small drop of liquid onto the slide
2. use tweezers to place the specimen on top
3. place the cover slip at a 45 degree angle to the slide and lower onto it (to prevent air bubbles)
4. add a stain by placing a drop next to one edge of the cover slip and a piece of paper towel next to the opposite edge, to draw the stain across the specimen
34
what are 3 examples that wet mounts are used on?
- blood samples
- living specimens (e.g. tiny aquatic organisms)
- specimens that are in a liquid (usually water)
35
why might you need to stain a specimen?
- in order to view it clearly under a microscope (especially if its transparent)
- to allow different components of a cell to be seen clearly under a microscope
- to highlight metabolic processes
- to differentiate between living and dead cells
36
how does cellular staining work?
different parts of the cell take up more stain than others, allowing different parts of the cell to be seen
37
why may you need to use different stains?
you can use more than 1 stain as different stains are used to make different parts of the cell show up
38
name 3 examples of stains
- methylene blue
- cormine
- eosin
39
what color does methylene blue turn what?
turns cells/nuclei blue
40
what color does cormine turn what?
turns glycogen red
41
what color does eosin turn what?
turns cytoplasm pink
42
what is the plasma membrane?
a cell surface membrane
43
where is the plasma membrane found?
- on the surface of animal cells
- just inside the cell wall of plant and prokaryotic cells
44
what is the plasma membrane made of?
mainly lipids and protein
45
what is the function of the plasma membrane?
- it regulates the movement of substances into and out of the cell
- it has receptor molecules on it which allow it to respond to chemicals like hormones
46
what is the structure of the cell wall?
a rigid structure that surrounds plant cells
47
what is the cell wall made of?
mainly the carbohydrate cellulose
48
what is the function of the cell wall?
it supports plant cells
49
what is the structure of the nucleus?
- a large organelle surrounded by a nuclear envelope (double membrane)
- the nuclear envelope contains many pores
- the nucleus contains chromatin and often a nucleolus
50
what is chromatin made from?
DNA and proteins
51
what is the function of the nucleus?
- controls the cells activities (by controlling the transcription of DNA)
- it contains instructions to make proteins
- its pores allow substances (e.g. RNA) to move between the nucleus and cytoplasm
52
what is the function of the nucleolus?
to make ribosomes
53
what is the structure of the lysosome?
- a round organelle surrounded by a membrane
- it has no clear internal structure
- it contains digestive enzymes which are kept separate from the cytoplasm by the surrounding membrane
54
what is the function of the lysosome?
- to digest invading cells
- to breakdown worn out components of the cell
55
what is the structure of the ribosome?
- a very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum
- it is not surrounded by a membrane
56
what is the ribosome made up of?
proteins and RNA
57
what is the function of the ribosome?
it is the site where proteins are made
58
what is the structure of the rough endoplasmic reticulum (RER)?
- a system of membranes enclosing a fluid filled space
- the surface is covered with ribosome's
59
what is the function of the rough endoplasmic reticulum (RER)?
it folds and process is proteins that have been made at the ribosomes
60
what is the structure of the smooth endoplasmic reticulum (SER)?
- a system of membranes enclosing a fluid filled space
- it has no ribosome's
61
what is the function of the smooth endoplasmic reticulum (SER)?
it synthesizes and process is lipids
62
what is the structure of the vesicle?
- a small fluid filled sac in the cytoplasm
- it is surrounded by a membrane
63
what is the function of the vesicle?
it transports substances in and out of the cell via the plasma membrane and between organelles
64
where are vesicles formed?
- some are formed by the golgi apparatus or the endoplasmic reticulum
- others are formed at the cell surface
65
what is the structure of the golgi apparatus?
- a group of fluid filled, membrane bound, flattened sacs
- vesicles are often seen at the edges of the sacs
66
what is the function of the golgi apparatus?
- it processes and packages new lipids and proteins
- it makes lysozymes
67
what is the structure of the mitochondria?
- usually oval shaped
- it has a double membrane (the inner one is folded to form structures called cristae)
- it has a matrix inside which contains enzymes involved in respiration
68
what is the function of the mitochondria?
it is the site of aerobic respiration (where ATP is produced)
69
where are mitochondria found?
- in cells that are very active and require a lot of energy
- they are found in large numbers
70
what is the structure of the chloroplast?
- small, flattened structure found in plant cells
- it is surrounded by a double membrane
- it has membranes inside called thylakoid membranes
- thylakoid membranes are stacked up in some parts of the chloroplast to form grana
- grana are linked together by lamellae
71
what are lamellae?
thin, flat pieces of thylakoid membrane
72
what is the function of the chloroplast?
the site of photosynthesis (some parts happen in the grana and other parts happen in the stroma)
73
what is the stroma?
a thick fluid found in chloroplasts
74
what is the structure of the centriole?
small, hollow cylinders
75
what are centrioles made of?
microtubules (tiny protein cylinders)
76
where are centrioles found?
- in animal cells
- in only some plant cells
77
what is the function of the centriole?
it is involved with the separation of chromosomes during cell division
78
what is the structure of the cilia?
- small, hairlike structures
- in cross section, they have an outer membrane and a ring of nine pairs of protein microtubules inside, with a single pair of microtubules the middle
79
what is the function of the microtubules?
they allow the cilia to move
80
what is the function of the cilia?
the movement from the microtubules is used by the cell to move substances along the cell surface
81
where are the cilia found?
on the surface membrane of some animal cells
82
what is the structure of the flagellum?
- they have a similar structure to cilia but are longer
- they stick out from the cell surface
- they are surrounded by the plasma membrane
83
what is the function of the flagellum?
- their microtubules contract to make the flagellum move
- flagella are used like outboard motors to propel the cells forward (e.g. when a sperm cell swims)
84
what are prokaryotic cells?
small and simple cells
85
what are eukaryotic cells?
- complex cells (including all plan and animal cells)
- usually have more organelles than prokaryotic cells
86
draw and label an animal cell
p30
87
draw and label a plant cell
p31
88
what additional organelles do plants have, that animals do not?
- a cell wall with plasmodesmata (channels for exchanging substances between adjacent cells)
- a vacuole (containing cell sap)
- chloroplasts (for photosynthesis)
89
what are the differences between prokaryotic and eukaryotic cells?
Prokaryotic cells
- extremely small (<2um diameter)
- circular DNA free in cytoplasm
- no nucleus
- cell wall made of polysaccharide
- few organelles and no membrane-bound organelles
- flagella (when present) made of the protein flagellin, arranged in a helix
- small ribosomes (≤20nm)
- e.g. E.coli bacterium, salmonella bacterium
Eukaryotic cells
- larger (10-100um diameter)
- linear DNA in nucleus
- nucleus present
- cell wall made of cellulose (plants) or chitin (fungi) or not present (animals)
- many organelles and membrane-bound organelles present (mitochondria)
- flagella (when present) made of microtubules, arranged in a 9+2 formation
- larger ribosomes (>20nm)
- e.g. human liver cell, yeast, amoeba
90
draw and label a bacteria cell (under an electron microscope)
p38
91
where are proteins made
proteins are made at ribosomes:
- the ribosomes on the rough endoplasmic reticulum (RER) make proteins that are excreted or attached to the cell membrane
- the free ribosomes in the cytoplasm make proteins that stay in the cytoplasm
92
describe the process of protein production
- new proteins produced at the RER are folded and processed (e.g. new sugar chains are added) in the RER
- then, they are transported from the RER to the golgi apparatus in vesicles
- at the golgi apparatus, the proteins may undergo further processing (e.g. sugar chains are trimmed or more added)
- then, the proteins enter more vesicles to be transported around the cell (e.g. glycoproteins - found in mucus - move to the cell surface and secreted)
93
draw and label a diagram of protein production
p36
94
what is the cytoskeleton?
a network of protein threads running through the cytoplasm
95
how is the cytoskeleton arranged in eukaryotic cells?
the protein threads are arranged as microfilaments and microtubules
96
what are microfilaments?
very thin protein strands
97
what are microtubules?
tiny protein cylinders
98
what are the cytoskeletons 4 main functions?
- the microtubules and microfilaments support the cells organelles, keeping them in position
- they help to strengthen the cell and maintain its shape
- they are also responsible for the transport of organelles and materials within the cell
- the proteins of the cytoskeleton can cause the cell to move
99
what are 2 examples of how the cytoskeleton can transport organelles and materials within the cell?
- the movement of chromosomes when they separate during cell division depends on contraction of microtubules in the spindle
- the movement of vesicles around the cell relies on the cytoskeletal proteins
100
name 2 organelles that move due to the cytoskeletal proteins
- cilia
- flagella
101
what does a diagram of the cytoskeleton in eukaryotic cells look like?
p37
