2.1.1 cell structure Flashcards
(118 cards)
1
Q
define: eukaryotic organisms
A
multi-cellular organisms made of eukaryotic cells e.g. animal and plant cells
2
Q
define: prokaryotic organisms
A
single-celled organisms made from prokaryotic cells e.g. bacteria
3
Q
function of cytoskeleton
A
- providing mechanical strength to cells
- aiding transport within cells
- enabling cell movement
4
Q
function of intermediate fibers
A
gives strength to cells and helps maintain integrity
5
Q
function of microfilaments
A
fibers are made from the protein, actin responsible for movement of the cell and cytoplasm during cytokinesis
6
Q
function of microtubules
A
- formed by the globular protein, tubulin polymerise to form tubes that determine the shape of the cell
- act as tracts for organelles moving around the cell forms organelles like centrioles and cilia
7
Q
function of microvilli
A
- found in specialised animal cells
- used to increase surface area of cell surface membrane to increase rate of exchange of substances
8
Q
function of mitochondria
A
- site of aerobic respiration
- as a result of respiration, they release ATP (energy carrier in cells)
9
Q
function of nucleus
A
- controls all the activity of the cell
- where the genetic code (DNA) of the cell is stored, replicated and copied into RNA (transcribed) the nucleus is attached to the rough ER so the mRNA can easily get to ribosomes
10
Q
function of ribosomes
A
- protein synthesis (where proteins are made)
- assemble amino acids into proteins in chains using mRNA
11
Q
function of rough endoplasmic reticulum
A
site of protein synthesis
12
Q
function of smooth endoplasmic reticulum
A
responsible for carbohydrates and lipid synthesis and storage
13
Q
structure of microtubules
A
- found in eukaryotic cells
- makes up cytoskeleton of cell
- made of α and β tubulin combined to form dimers which join to protofilaments
14
Q
structure of microvilli
A
cell membrane projections
15
Q
structure of mitochondria
A
- oval shaped
- surrounded by two
membranes (double membrane) - the inner membrane forms finger-like structure called cristae which increases the surface area
- the solution inside is called a matrix which contains enzymes for respiration
- mitocondrial DNA - small amounts of DNA, enable mitochondrion to reproduce and create enzymes
16
Q
structure of ribosomes
A
- a 2 subunit organelle
- made from RNA and protein
- not membrane bound
- very small organelles (around 22nm in diameter)
- found free floating in the cytoplasm or attached to the RER
- 80S ribosomes => eukaryotic cells
- 70S ribosomes => prokaryotic cells, mitochondria and chlorplasts
17
Q
structure of rough endoplasmic reticulum
A
- stacks of membrane bound (fluid filled) sacs which form sheets called cisternae
- attached to the nucleus and covered with ribosomes
- consists of an interconnected system of flattened sacs
18
Q
structure of smooth endoplasmic reticulum
A
similar to RER but lacks ribosomes - a system of interconnected tubules
19
Q
what are nuclear pores?
A
allows molecules to enter (e.g. nucleotides for DNA replication) and leave the cell e.g. mRNA leaves the cell
20
Q
what are the 3 structural components to the cytoskeleton?
A
microfilaments
microtubules
intermediate fibers
21
Q
what is chromatin?
A
the DNA (with associated histone proteins) contains the genetic code which controls the activity of the cell
22
Q
what is the double nuclear envelope?
A
a double membrane which compartmentalises the nucleus and prevents damage and protects the DNA
23
Q
what is the nucleolus?
A
site of ribosome production
composed of RNA and proteins
24
Q
function of cell-surface membrane
A
- regulates the movement of substances into and out of the cell
- contains receptor molecules which allow it to respond to chemicals like hormones
25
function of cellulose cell wall
- gives the plant mechanical strength
- gives the plant cell support and its shape
- contents of the plant cell can 'push' against cell wall (turgid cell) - gives the cell and whole plant good support
26
function of centrioles
makes a copy of itself during cell division and then helps to form the spindle in cell division
27
function of chloroplasts
- photosynthetic reactions
- contains chlorophyll
- light-dependent stage takes place in the thylakoids
- light-independent stage takes place in stroma
28
function of cilia
- sensory function (e.g. nose), beat creating a current to move fluid/mucous/objects
- for locomotion
- allows the movement of substances over the cell surface
29
function of flagella
- whip-like - enables a cells mobility
- the microtubules contract to make the flagellum move
- propel cells forward e.g. sperm cell
30
function of golgi apparatus
- allows internal transport
- receives proteins from the RER
- modifies and processes molecules (such as new lipid and proteins) and packages them into vesicles
- these may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell)
- makes lysosomes
- lipid synthesis
31
function of large permanent vacuole
- stores cell sap
- support herbaceous plants by making cells turgid
- helps maintain shape and gives support by maintaining turgor pressure
- sugars and amino acids act as a temporary food store
32
function of lysosomes
- contain powerful hydrolytic digestive enzymes known as lysozymes
- their role is to break down worn out components of the cell or digest invading cells
33
structure and function of vesicles
- found in plant and animal cells
- a membrane-bound sac for transport and storage
34
structure of cell-surface membrane
- the membrane found of the surface of animal cells and inside the cell wall of plant and prokaryotic cells
- a phospholipid bilayer
- composed of proteins and lipids
35
structure of cellulose cell wall
- made of beta-cellulose microfibrils - complex carbohydrates
- cell wall is fully permeable to substances
- thin layer called the middle lamella which marks the boundary between adjacent cell walls and 'cements' adjacent cells together
36
structure of centrioles
- a component of the cytoskeleton composed of many microtubules
- small, hollow cylinders that occurs in pairs next to the nucleus in animals cells only
- each centriole contains a ring of 9 microtubules
37
structure of nucleus
- consists of a double-layered nuclear membrane or envelope that separates the nucleus from the cytoplasm
- connected to endoplasmic reticulum
38
structure of chloroplasts
- larger than mitochondria
- surrounded by a double membrane
- membrane-bound compartments called thylakoids contain chlorophyll
- thylakoids stack to form grana
- contains small circular DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
39
structure of cilia
- hair-like extensions that protrude from some animal cell types
- in cross section, they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle
- known as a 9+2 arrangement
- arrangement allows movement
40
structure of flagella
- similar to cilia but longer
- they protrude from the cell surface area and are surrounded by the plasma membrane
- 9+2 arrangement
41
structure of golgi apparatus
- stacks of flattered, membrane bound sacs (cisternae)
- these are continuously formed from the ER at one end and budding off as golgi vesicles at the other
42
structure of large permanent vacuole
- single membrane bound (membrane called tonoplast)
- contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc)
- selectively permeable barrier
43
structure of lysosomes
they are spherical sacs surrounded by a single membrane
44
magnification equation
image size = actual size x magnification
45
define resolution
Resolution is the ability to distinguish between objects that are close together (i.e. the ability to see two structures that are very close together as two separate structures)
46
define magnification
Magnification tells you how many times bigger the image produced by the microscope is than the real-life object you are viewing
47
different types of microscopes
light
electron
laser scanning confocal
48
what is optical/ light microscopes
- use light to form an image
49
resolution of light microscopes
limited resolution
hard to resolve objects closer than half the wavelength of light
max resolution around 200nm
50
magnification of light microscopes
x1500
51
what are light microscopes used for?
can be used to observe eukaryotic cells, nuclei
sometimes mitochondria and chloroplasts
52
how do light microscopes work?
- light is directed through the thin layer of organism supported on a glass slide
- light is focused through several lenses to make the image visible through the eyepiece
- magnifying power can be increased
53
advantages of light microscopes
- produces colour images
- relatively cheap to buy and operate
- living and dead specimens can be viewed
- doesn't require expertise to operate
54
disadvantage of light microscopes
- limited resolution
- limited magnification
- difficulty in observing internal structures within cells.
55
what are electron microscopes?
use electrons to form an image
56
resolution of electron microscope
increases resolution - more detailed image
max resolution of 0.2nm
57
magnification of electron microscopes
max magnification x1,500,000
58
types of electron microscope
transmission and scanning
59
what are electron microscopes used for?
used to observe small organelles such as ribosomes, endoplasmic reticulum or lysosomes
60
how do transmission electron microscopes work?
use electromagnets to focus a beam of electrons
transmitted through the specimen
denser parts of the specimen absorb more electrons making them appear darker
61
advantages of TEMs
- high resolution images
- allows internal structures within cells to be seen
62
disadvantages of TEMs
- only be used with thin specimens
- cannot be used to observe live specimens (vacuum inside that removes water)
- lengthy treatment to prepare artefacts
- do not produce colour images
63
how do scanning electron microscopes work?
scan a beam of electrons across the specimen
beam bounces off the surface of the specimen and the electrons detected form an image
can produce 3D images
64
advantages of SEMs
- used on thick or 3D specimens
- produces 3D images that show the surface of specimens
65
disadvantages of SEMs
- lower resolution images than TEMs
- cannot be used to observe live specimens
- do not produce a colour image
66
what are laser scanning confocal microscopes?
relatively new technology
thick section of tissue or organisms are scanned with a laser beam
67
how do laser scanning confocal microscopes work?
- cells must be stained with fluorescent dyes
- thick section of tissue or organisms are scanned with a laser beam
- beam is reflected by the fluorescent dyes
- multiple depths of the organism is scanned to produce an image
68
advantages of laser scanning confocal microscopes
- used on thick or 3D specimens
- produces 3D image of structure
- high resolution as laser beam can be focused at specific depths
69
disadvantages of laser scanning confocal microscopes
- slow process and takes time to obtain an image
- laser may cause photodamage to the cells
70
name the key components of a light microscope
- eyepiece lens
- objective lenses
- stage
- light source
- coarse and fine focus
71
what is the coarse focus for?
used to focus the low and medium power objective lenses
72
what is the fine focus for?
used to focus the high power objective lens
73
what does the turret do?
rotates to bring the objective lenses into place
74
what magnification does the objective lenses come in?
x4 (low)
x10 (medium)
x40 (high)
75
what is the stage for?
where the microscope slide goes
76
what is the condenser for?
used to vary the intensity of light reaching the object
77
method of preparing a slide for a liquid specimen
- add a few drops of the sample to the slide
- cover the smear with a coverslip and gently press down to remove air bubbles
- wear gloves to ensure no cross-contamination of foreign cells
78
method of preparing a slide for a solid specimen
- take care when using sharp objects and wear gloves to prevent stains dying skin
- use scissors to cut a sample sample of tissue
- peel away thin layer of cells and place on slide
- apply a stain
- place a coverslip on top and press down to remove air bubbles
79
alternative ways to preparing a slide for a solid specimen
- may need to be treated with chemicals to kill the tissue - using a microtome
- may need to freeze specimen and cut using a cryostat
THEN
- place specimen on slide
- add stain
- place coverslip on top to remove air bubbles
80
why must you start with a low power objective lens when using an optical microscope?
easier to find what to look for
helps to prevent damage to lens
81
how to prevent dehydration of tissue?
add drops of water to specimen to prevent cells from being damaged by dehydration
82
how to solve unclear or blurry images?
switch to low power objective lens
use coarse focus to get clearer image
check if specimen is thin enough for light to pass through
check for cross-contamination with foreign cells
83
what is a graticule
small disc with engraved ruler
used to take measurements of cells
84
how to use a graticule?
- placed into eyepiece of microscope
- must be calibrated using a stage micrometer
- use two scales together the number of micrometers each graticule unit is worth can be worked out
85
limitations of graticules
- size of cells and structures may appear inconsistent in different specimen slides
- only used on light microscopes so some structures may not be seen
- treatment of specimens when preparing slides could alter structure of cells
86
why are stains used in microscopy?
used to make tissue visible to make it easier to see detail of tissue when light passes through
87
staining for light microscopes
- dyes used absorb specific colours of light while reflecting others
- certain tissues absorb certain dyes
88
what is differential staining?
stained with multiple dyes to ensure the different tissues show up
89
when may stains not be required?
when looking at chloroplasts
dont need stains as they show up green (natural colour)
90
commonly used stains for light microscopes
toluidine blue
phloroglucinol
91
what does toluidine blue dye do?
turns cells blue
92
what does phloroglucinol dye do?
turns cells red/pink
93
staining for electron microscopy
- must be stained in order to absorb electrons
- heavy-metal compounds commonly used as dyes as they absorb electrons well - electrons have no colour and so show up black/grey
- colour present in electron micrographs is not natural - colour is added to image
94
commonly used dyes for electron microscopes
osmium tetroxide
ruthenium tetroxide
95
convert 1 micrometre to nanometres
1 µm = 1,000 nm
96
convert 1 millimetre to micrometres
1mm = 1,000 µm
97
convert 1 metre to millimetres
1 m = 1,000 mm
98
comparison of light and electron microscopes: size
light: small and easy to carry
electron: large and cannot be moved
99
comparison of light and electron microscopes: vacuum
light: no vacuum required
electron: vacuum required
100
comparison of light and electron microscopes: sample prep
light: easy sample preparation
electron: complicated sample preparation
101
comparison of light and electron microscopes: magnification
light: up to x2,000 mag
electron: over x500,000 mag
102
comparison of light and electron microscopes: resolution
light: 200nm
electron: 0.5nm
103
comparison of light and electron microscopes: specimen
light: living or dead specimens
electron: dead specimens
104
what organelles are involved in protein synthesis
nucleus
ribosomes
RER
golgi apparatus
cell surface membrane
105
process of secretion of proteins
(1) Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum.
(2) They then pass into its cisternae and are packaged into transport vesicles.
(3) Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton.
(4) The vesicles fuse with the cis face of the Golgi apparatus and the proteins enter. The proteins are structurally modified before leaving the Golgi apparatus from vesicles in its trans face.
(5) Secretory vesicles carry proteins that are to be released from the cell. The vesicles move towards and fuse with the cell-surface membrane, releasing their contents via exocytosis. Some vesicles form lysosomes - these contain enzymes for use in the cell.
106
process of secretion of protein
1. proteins are synthesised on the ribosomes bound to the rough endoplasmic reticulum
2. they then pass into its cisternae and are packaged into transport vesicles
3. vesicles containing the newly synthesised proteins move towards the golgi apparatus via the transport function of the cytoskeleton
4. the vesicles fuse with the cis face of the golgi apparatus and the proteins enter. the proteins are structurally modified before leaving the golgi apparatus in vesicles from its trans face.
5. secretory vesicles carry proteins that are to be released from the cell. the vesicles move towards and fuse with the cell-surface membrane, releasing their contents by exocytosis. some vesicles form lysosomes - these contain enzymes for use in the cell
107
rules for biological drawings
1. use sharp pencil
2. use at least half the space
3. lines must be clear and continuous
4. ensure proportions are correct
5. label areas of tissue shown in pen
6. rule the label lines in pencil
7. make sure label lines touch area you are labelling (no arrowheads)
8. annotations - add note around features on drawing
9. use a scale bar
10. include a title
11. no shading
12. include magnification
108
comparison of prokaryotic and eukaryotic cells: nucleus
pro: not present
euk: present
109
comparison of prokaryotic and eukaryotic cells: DNA
pro: circular
euk: linear
110
comparison of prokaryotic and eukaryotic cells: DNA organisation
pro: proteins fold and condense DNA
euk: associated with proteins called histones
111
comparison of prokaryotic and eukaryotic cells: extra chromosomal DNA
pro: circular DNA called plasmids
euk: only present in certain organelles such as chloroplasts and mitochondria
112
comparison of prokaryotic and eukaryotic cells: organelles
pro: non membrane-bound
euk: both membrane-bound and non membrane-bound
113
comparison of prokaryotic and eukaryotic cells: cell wall
pro: peptidoglycan
euk: chitin in fungi, cellulose in plants, not present in animals
114
comparison of prokaryotic and eukaryotic cells: ribosomes
pro: smaller 70S
euk: larger 80S
115
comparison of prokaryotic and eukaryotic cells: cytoskeleton
pro: present
euk: present, more complex
116
comparison of prokaryotic and eukaryotic cells: reproduction
pro: binary fission
euk: asexual or sexual
117
comparison of prokaryotic and eukaryotic cells: cell type
pro: unicellular
euk: unicellular and multicellular
118
comparison of prokaryotic and eukaryotic cells: cell-surface membrane
pro: present
euk: present
