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2.1.1 cell structure Flashcards

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1
Q

define: eukaryotic organisms

A

multi-cellular organisms made of eukaryotic cells e.g. animal and plant cells

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2
Q

define: prokaryotic organisms

A

single-celled organisms made from prokaryotic cells e.g. bacteria

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3
Q

function of cytoskeleton

A
  • providing mechanical strength to cells
  • aiding transport within cells
  • enabling cell movement
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4
Q

function of intermediate fibers

A

gives strength to cells and helps maintain integrity

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5
Q

function of microfilaments

A

fibers are made from the protein, actin responsible for movement of the cell and cytoplasm during cytokinesis

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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
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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
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8
Q

function of mitochondria

A
  • site of aerobic respiration
  • as a result of respiration, they release ATP (energy carrier in cells)
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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
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10
Q

function of ribosomes

A
  • protein synthesis (where proteins are made)
  • assemble amino acids into proteins in chains using mRNA
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11
Q

function of rough endoplasmic reticulum

A

site of protein synthesis

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12
Q

function of smooth endoplasmic reticulum

A

responsible for carbohydrates and lipid synthesis and storage

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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
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14
Q

structure of microvilli

A

cell membrane projections

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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
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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
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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
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18
Q

structure of smooth endoplasmic reticulum

A

similar to RER but lacks ribosomes - a system of interconnected tubules

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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

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20
Q

what are the 3 structural components to the cytoskeleton?

A

microfilaments
microtubules
intermediate fibers

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21
Q

what is chromatin?

A

the DNA (with associated histone proteins) contains the genetic code which controls the activity of the cell

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22
Q

what is the double nuclear envelope?

A

a double membrane which compartmentalises the nucleus and prevents damage and protects the DNA

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23
Q

what is the nucleolus?

A

site of ribosome production
composed of RNA and proteins

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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
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25
Q

function of cellulose cell wall

A
  • 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
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26
Q

function of centrioles

A

makes a copy of itself during cell division and then helps to form the spindle in cell division

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27
Q

function of chloroplasts

A
  • photosynthetic reactions
  • contains chlorophyll
  • light-dependent stage takes place in the thylakoids
  • light-independent stage takes place in stroma
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28
Q

function of cilia

A
  • 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
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29
Q

function of flagella

A
  • whip-like - enables a cells mobility
  • the microtubules contract to make the flagellum move
  • propel cells forward e.g. sperm cell
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30
Q

function of golgi apparatus

A
  • 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
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31
Q

function of large permanent vacuole

A
  • 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
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32
Q

function of lysosomes

A
  • contain powerful hydrolytic digestive enzymes known as lysozymes
  • their role is to break down worn out components of the cell or digest invading cells
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33
Q

structure and function of vesicles

A
  • found in plant and animal cells
  • a membrane-bound sac for transport and storage
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34
Q

structure of cell-surface membrane

A
  • 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
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35
Q

structure of cellulose cell wall

A
  • 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
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36
Q

structure of centrioles

A
  • 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
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37
Q

structure of nucleus

A
  • consists of a double-layered nuclear membrane or envelope that separates the nucleus from the cytoplasm
  • connected to endoplasmic reticulum
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38
Q

structure of chloroplasts

A
  • 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
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39
Q

structure of cilia

A
  • 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
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40
Q

structure of flagella

A
  • similar to cilia but longer
  • they protrude from the cell surface area and are surrounded by the plasma membrane
  • 9+2 arrangement
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41
Q

structure of golgi apparatus

A
  • 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
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42
Q

structure of large permanent vacuole

A
  • single membrane bound (membrane called tonoplast)
  • contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc)
  • selectively permeable barrier
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43
Q

structure of lysosomes

A

they are spherical sacs surrounded by a single membrane

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44
Q

magnification equation

A

image size = actual size x magnification

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45
Q

define resolution

A

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)

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46
Q

define magnification

A

Magnification tells you how many times bigger the image produced by the microscope is than the real-life object you are viewing

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47
Q

different types of microscopes

A

light
electron
laser scanning confocal

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48
Q

what is optical/ light microscopes

A
  • use light to form an image
49
Q

resolution of light microscopes

A

limited resolution
hard to resolve objects closer than half the wavelength of light
max resolution around 200nm

50
Q

magnification of light microscopes

A

x1500

51
Q

what are light microscopes used for?

A

can be used to observe eukaryotic cells, nuclei
sometimes mitochondria and chloroplasts

52
Q

how do light microscopes work?

A
  • 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
Q

advantages of light microscopes

A
  • produces colour images
  • relatively cheap to buy and operate
  • living and dead specimens can be viewed
  • doesn’t require expertise to operate
54
Q

disadvantage of light microscopes

A
  • limited resolution
  • limited magnification
  • difficulty in observing internal structures within cells.
55
Q

what are electron microscopes?

A

use electrons to form an image

56
Q

resolution of electron microscope

A

increases resolution - more detailed image
max resolution of 0.2nm

57
Q

magnification of electron microscopes

A

max magnification x1,500,000

58
Q

types of electron microscope

A

transmission and scanning

59
Q

what are electron microscopes used for?

A

used to observe small organelles such as ribosomes, endoplasmic reticulum or lysosomes

60
Q

how do transmission electron microscopes work?

A

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
Q

advantages of TEMs

A
  • high resolution images
  • allows internal structures within cells to be seen
62
Q

disadvantages of TEMs

A
  • 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
Q

how do scanning electron microscopes work?

A

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
Q

advantages of SEMs

A
  • used on thick or 3D specimens
  • produces 3D images that show the surface of specimens
65
Q

disadvantages of SEMs

A
  • lower resolution images than TEMs
  • cannot be used to observe live specimens
  • do not produce a colour image
66
Q

what are laser scanning confocal microscopes?

A

relatively new technology
thick section of tissue or organisms are scanned with a laser beam

67
Q

how do laser scanning confocal microscopes work?

A
  • 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
Q

advantages of laser scanning confocal microscopes

A
  • used on thick or 3D specimens
  • produces 3D image of structure
  • high resolution as laser beam can be focused at specific depths
69
Q

disadvantages of laser scanning confocal microscopes

A
  • slow process and takes time to obtain an image
  • laser may cause photodamage to the cells
70
Q

name the key components of a light microscope

A
  • eyepiece lens
  • objective lenses
  • stage
  • light source
  • coarse and fine focus
71
Q

what is the coarse focus for?

A

used to focus the low and medium power objective lenses

72
Q

what is the fine focus for?

A

used to focus the high power objective lens

73
Q

what does the turret do?

A

rotates to bring the objective lenses into place

74
Q

what magnification does the objective lenses come in?

A

x4 (low)
x10 (medium)
x40 (high)

75
Q

what is the stage for?

A

where the microscope slide goes

76
Q

what is the condenser for?

A

used to vary the intensity of light reaching the object

77
Q

method of preparing a slide for a liquid specimen

A
  • 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
Q

method of preparing a slide for a solid specimen

A
  • 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
Q

alternative ways to preparing a slide for a solid specimen

A
  • 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
Q

why must you start with a low power objective lens when using an optical microscope?

A

easier to find what to look for
helps to prevent damage to lens

81
Q

how to prevent dehydration of tissue?

A

add drops of water to specimen to prevent cells from being damaged by dehydration

82
Q

how to solve unclear or blurry images?

A

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
Q

what is a graticule

A

small disc with engraved ruler
used to take measurements of cells

84
Q

how to use a graticule?

A
  • 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
Q

limitations of graticules

A
  • 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
Q

why are stains used in microscopy?

A

used to make tissue visible to make it easier to see detail of tissue when light passes through

87
Q

staining for light microscopes

A
  • dyes used absorb specific colours of light while reflecting others
  • certain tissues absorb certain dyes
88
Q

what is differential staining?

A

stained with multiple dyes to ensure the different tissues show up

89
Q

when may stains not be required?

A

when looking at chloroplasts
dont need stains as they show up green (natural colour)

90
Q

commonly used stains for light microscopes

A

toluidine blue
phloroglucinol

91
Q

what does toluidine blue dye do?

A

turns cells blue

92
Q

what does phloroglucinol dye do?

A

turns cells red/pink

93
Q

staining for electron microscopy

A
  • 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
Q

commonly used dyes for electron microscopes

A

osmium tetroxide
ruthenium tetroxide

95
Q

convert 1 micrometre to nanometres

A

1 µm = 1,000 nm

96
Q

convert 1 millimetre to micrometres

A

1mm = 1,000 µm

97
Q

convert 1 metre to millimetres

A

1 m = 1,000 mm

98
Q

comparison of light and electron microscopes: size

A

light: small and easy to carry
electron: large and cannot be moved

99
Q

comparison of light and electron microscopes: vacuum

A

light: no vacuum required
electron: vacuum required

100
Q

comparison of light and electron microscopes: sample prep

A

light: easy sample preparation
electron: complicated sample preparation

101
Q

comparison of light and electron microscopes: magnification

A

light: up to x2,000 mag
electron: over x500,000 mag

102
Q

comparison of light and electron microscopes: resolution

A

light: 200nm
electron: 0.5nm

103
Q

comparison of light and electron microscopes: specimen

A

light: living or dead specimens
electron: dead specimens

104
Q

what organelles are involved in protein synthesis

A

nucleus
ribosomes
RER
golgi apparatus
cell surface membrane

105
Q

process of secretion of proteins

A

(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
Q

process of secretion of protein

A
  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
Q

rules for biological drawings

A
  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
Q

comparison of prokaryotic and eukaryotic cells: nucleus

A

pro: not present
euk: present

109
Q

comparison of prokaryotic and eukaryotic cells: DNA

A

pro: circular
euk: linear

110
Q

comparison of prokaryotic and eukaryotic cells: DNA organisation

A

pro: proteins fold and condense DNA
euk: associated with proteins called histones

111
Q

comparison of prokaryotic and eukaryotic cells: extra chromosomal DNA

A

pro: circular DNA called plasmids
euk: only present in certain organelles such as chloroplasts and mitochondria

112
Q

comparison of prokaryotic and eukaryotic cells: organelles

A

pro: non membrane-bound
euk: both membrane-bound and non membrane-bound

113
Q

comparison of prokaryotic and eukaryotic cells: cell wall

A

pro: peptidoglycan
euk: chitin in fungi, cellulose in plants, not present in animals

114
Q

comparison of prokaryotic and eukaryotic cells: ribosomes

A

pro: smaller 70S
euk: larger 80S

115
Q

comparison of prokaryotic and eukaryotic cells: cytoskeleton

A

pro: present
euk: present, more complex

116
Q

comparison of prokaryotic and eukaryotic cells: reproduction

A

pro: binary fission
euk: asexual or sexual

117
Q

comparison of prokaryotic and eukaryotic cells: cell type

A

pro: unicellular
euk: unicellular and multicellular

118
Q

comparison of prokaryotic and eukaryotic cells: cell-surface membrane

A

pro: present
euk: present

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