cell structure 2.1.1 Flashcards
1
Q
define magnification
A
the number of times larger the image is than the actual object
2
Q
define resolution
A
The ability to distinguish between two points
3
Q
what is the cell theory ?
A
- All organisms are composed of one or more cells
- Cells are the smallest units of life
- All cells come from pre-existing cells
4
Q
how do light microscopes work ?
A
visible light waves are passed through the sample, a stain is used to colour the cells so they are more visible
5
Q
which microscope has the lowest magnification and resolving power ?
A
light microscopes
6
Q
what type of sample can you use with a light microscope ?
A
living or dead sample
cells and large organelles
relatively thin so light can pass through
7
Q
what are the advantages of light microscopes ?
A
cheap, easy to use , quick
8
Q
what are the disadvantages of light microscopes ?
A
cant see small organelles ( restricted resolution )
cant magnify more than 2000 x
9
Q
what type of image do light microscopes make ?
A
2D , colour
10
Q
how does a scanning electron microscope work?
A
a beam of electrons scans the specimen from above, the specimen scatters the electrons according to its contour, these are detected so that the computer can form a 3D image
11
Q
what image does a scanning electron microscope form ?
A
3D , black and white
12
Q
how does a transmission electron microscope work ?
A
a focused beam of electrons is transmitted through a thin specimen, denser parts of the specimen absorb more electrons creating a darker image, others parts allow electrons through creating a lighter image.
13
Q
what image does a transmission electron microscope form ?
A
2D, black and white
14
Q
what are examples of artefacts ?
A
bubbles
distortion of organelles
mesosomes
empty space in the cytoplasm
loss of continuity in membranes
14
Q
which microscope has the highest magnification and resolution ?
A
transmission electron microscope
14
Q
what are the advantages of electron microscopes ?
A
very detailed, much higher resolution and magnifcation
15
Q
what is an artefact ?
A
an apparent structural detail that is caused by the processing of the specimen ( not a legitimate feature of the specimen )
16
Q
what are the disadvantages of electron microscopes ?
A
expensive and large
need special equipment and person with training
cant use live specimen as a vacuum is needed
the specimen can be damaged in preparation
17
Q
how do you calculate magnification ?
A
Image size divided by actual size
18
Q
how do you convert from millimetres too micrometres ?
A
x 1000
19
Q
how do you convert from micrometres to nanometres ?
A
x 1000
20
Q
how do you convert from micrometres to millimetres ?
A
divide by 1000
21
Q
how do you convert from nanometres to micrometres ?
A
divide by 1000
22
Q
how do you calculate overall magnification ?
A
eyepiece magnification x objective magnification
23
what is the structure of nucleus ?
largest organelle
one per cell
form chromatin from proteins called histones
24
what is the function of the nucleus ?
controls the metabolic activities of the cell
contains DNA and directs synthesis of proteins
25
what is the structure of lysosomes ?
a specialised type of vesicle that contains hydrochloric enzymes
26
what is the function of lysosomes ?
break down waste material in cells, including old organelles and pathogens injected by phagocytosis cells
role in programmed cell death (apoptosis)
27
what is the structure of the nucleolus ?
composed of proteins and RNA
28
what is the function of nucleolus ?
produces ribosomes
29
what is the structure nuclear envelope ?
the double membrane encasing the nucleus
contains gaps called nuclear pores
30
what is the function of the nuclear envelope ?
protects the DNA from damage in the cytoplasm
allows molecules to move in and out of the nucleus
31
what is the structure of mitochondria ?
2-5 micrometres long
have a double membrane which is highly folded and forms cristae
fluid in the middle is called the matrix
have circular DNA pieces (mtDNA) and contains ribosomes
32
what is the function on mitochondria ?
cellular respiration occurs here to release energy for the cell
can produce their own enzymes and reproduce themselves ( self replicating )
33
what is the structure of ribosomes ?
20nm diameter
on the rough ER or cytoplasm
made form RNA in the nucleus
2 subunits small and large
no membrane
mitochondria and chloroplasts contain them
34
what's the structure of cell surface membrane ?
7nm
made of phospholipid bilayer
partially permeable
fragile
35
what is the structure of the cell surface membrane ?
7nm
made of phosolipid bilaayer
36
what's the function of the cell surface membrane ?
boundary of all cells
controls what enters ( endocytosis ) and exits ( exocytosis ) the cell
37
what is the structure of the Golgi apparatus ?
compact structure formed of cisternae
38
what is the function of the Golgi apparatus ?
stores, modifies and packages proteins into vesicles
molecules transported to and from Golgi by vesicles
protein modification = adding sugar (glycoprotein) or adding lipids (lipoproteins)
39
what is the structure of the endoplasmic reticulum ?
network of membranes enclosing flatterened sacs calles cisternae
connected to the outer nuclear membrane
40
what is the function of the rough endoplasmic reticulum ?
ribosomes on the surface
processes proteins made by ribosomes
41
what is the function of the smooth endoplasmic reticulum ?
no ribosomes
involved in the lipid and carbohydrate synthesis and storage
42
what is the structure of vesicles ?
single membrane with fluid inside
43
what is the function of vesicles ?
membrane sacs with storage and transport roles
and transport materials inside the cell
44
what is the structure microtubules (cilia )?
park of the cytoskeleton
hair like
contain 2 microtubules surrounded by 9 in a wheel shape
45
what is the function of cilia ?
used to move substances around the body as they beat in synchrony
45
what is the structure of undulipodia ?
formed of microtubules
eukaryotic equivalent to flagella
whip like extensions found on sperm cells
46
what is the function of undulipodia ?
used as a sensory organelle to detect chemical changes in the cells enviroment
47
what is the structure of centrioles ?
only animal cells
hollow fibre made of microtubules
48
what is a centrosome ?
when two centrioles meet at right angles
49
what is the function of centrioles ?
aid in cell division by migrating to opposite sides of cells
50
what is the structure of a chloroplast ?
double membrane structure
fluid enclosed = stroma
thylakoids = flattened sacks of membranes which join to form grana and join again to form lamellae
has internal membranes which provide the large surface area needed foe enzymes, proteins and pigment molecules
51
what is the function of chloroplasts ?
absorb light which is a catalyst for photosynthesis using chlorophyll
52
what is the structure of cell wall ?
rigid and protective barrier
outside cell membrane
freely permeable
located on outside of plasma membrane
made of cellulose fibres
gaps called plasmodesmata
53
what the function of the cell wall ?
provide structural support
54
what is the structure of the vacuole ?
normally found in plant cells and is large and permanent
bound by a membrane called tonoplast
55
what is the function of the vacuole ?
Storage container for water, food, enzymes, wastes, pigments, etc
provides structure
56
why do cells make proteins ?
cells synthesise proteins for intenal use and secretion
57
what is secretion ?
transport out of the cell
58
decibe how protiens pass through the cell ?
proteins are synthesised on the ribosomes bound to the ER
they then pass into its cisternae and are packaged into transport vesicles
the vesicles contain the newly synthesised proteins move toward the golgi apparatus via the cytoplasm
the vesicles fuse with the cis face of the golgi apparatus and the proteins enter. they are structurally modified before leaving vesicles
secretory vesicle carry proteins to be released ,they fuse with the cell surface membrane releasing there contents by exocytosis in a process that requires energy .
some vesicles form lysosomes wich contain enzymes
59
what is the cytoskeleton?
present throughout the cytoplasm of all the eukaryotic cells
a network of fibres necessary for shape and structure of the cell
3 components- microfilements, microtubles, intermediate fibrrs
60
what are the key functions of the cytoskeleton ?
support the cells organelles keeping them in position
strengthen the cell and add mechanical strength
maintain the cell shape / stability /whole cell support
responsible for movement of materials within the cell eg. organelles ,vesicles
cell movement = exocytosis, endocytosis, phagocytoisi
61
what is the structure, size and function of microfilaments ?
structure = small solid strands, made of protein actin
size = 7nm diameter
functions = muscle contraction due to actin
reasonable for cell movement and cell contraction during cytokinesis
involved in phagocytosis
62
what is the structure, size and function of microtubules ?
structure = tiny protein cylinders - straight and hollow, made of protein globular tubulin
size = 18-30nm diameter
functions = act as tracks for the movement of organelles eg. vesicles
make up spindle fibres, centrioles , cilia and flagella
63
how is cellular movement accomplished ?
cilia - hair like structures which beat in synchrony to move unicellular organisms eg. in trachea or oviduct
undulipodia = whip like appendages that undulate to move cells eg. on sperm cells
64
what is the arrangement of microtubules in eukaryotes ?
9 + 2 arrangement
65
what are intermediate fibres/filaments ?
give mechanical strength to cells and help maintain the integrity
10nm diameter
66
what is the motor protein for microfilaments ?
myosin interacts with actin to enable muscle contraction
67
what are the motor proteins for microtubules ?
dynein which allows cilia/undulipodia to move when it interacts with tubulin
(defective dynein in males causes infertility or infections in the raspatory tract )
kinesin interacts with tubulin to move vesicles
68
what is a motor protein ?
molecular motors that use the cytoskeleton to move along the cytoplasm of a cell
69
what is a eukaryote ?
a cell that contains membrane bound organelles eg. nucleus, mitochondria, vacuole, chloroplast ,ER, Golgi apparatus
70
what is a prokaryote ?
a cell without a nucleus and no membrane bound organelles.
unicellular
classed into two groups archaea and bacteria
smaller ribosomes
less developed cytoskeleton
smaller
sometimes have - plasmids, waxy capsule, pili, flagella
71
what is the endosymbiont theory ?
when a prokaryote eats a smaller one, the smaller one has a way to avoid being digested and lives inside the host cell, both cells benefit from the arrangement which makes it mutualistic and symbiotic relationship. the bacteria divides and the internal bacteria is passed on to the next generation
eg. this formed mitochondria and chloroplasts
72
what are the different ways to prepare slides ?
dry mount , wet mount , squash slide , smear slide
73
what is a eyepiece graticule ?
a glass disc marked with a fine scale of numbers but no units
74
what is calibration ?
to mark ( an instrument ) with a standard set of readings
75
what is the purpose of staining ?
increase the contrast as different components within a cell take up the stain to different degrees, or to make transparent organelles visible
76
what are positively and negatively charged dyes ?
+ charged dyes are attracted to the - materials which stains the cell components
- charged dyes are repelled by the - materials eg. the cytosol. so it stains the outside of cells
77
what is differential staining ?
can distinguish between two types of organisms which would be hard to identify otherwise
78
explain the gram stain technique
it is used to seperate bacteria into gram postitive and gram negative.
1.crystal violet is applied , the cells with thick walls retains the stain and go blue
2. iodine is added to fix the dye in place
3. the sample is then washed with alcohol, the stain will be washed out of the cells with thin walls , show colourless
4. stafin then dyes the colourless cells red
79
explain the acid fast technique
used to identify microbacterium from other bacteria
1. carbolfuchsin is applied which dyes all the cells red
2. a decolouriser (acid alcohol) is added to cause non acid fast cells to loose the red colour
3. a counter stain (methylene blue) dyes the non acid fast cells blue
4. results are : acid fast cells = red, non acid fast cells = blue
80
81
what are examples of stains ?
crystal violet is a positive dye which is attracted to the negative materials in the cytoplasm, leading to the staining of cell components
methylene blue : positive dye, stains DNA
Congo red : negative , stains the background of cells
acetic orcein : binds to DNA and dyes chromosomes dark red
eosin : stains the cytoplasm dark red / pink
haematoxylin : used with eosin and it stains the DNA/RNA a blue purple
Sudan red : stains lipids red
iodine : stains starch a blue black
potassium iodine solution : stains cellulose yellow
toluidine blue : stains different parts of the cell different colours
