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OCR A level Biology > 2.1.1 - Cell Structure > Flashcards

2.1.1 - Cell Structure Flashcards

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1
Q

What does a microscope allow us to do

A

Magnify an object many times

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2
Q

Eyepiece graticule

A

Circular disk that fits onto the eyepiece and contains a tiny ruler with equal divisions on it

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3
Q

Stage micrometer

A

Usually 1-100nm long with 100 divisions on it. This sits on the stage of the microscope and is used to calibrate the eyepiece graticule

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4
Q

Why do we need a stage micrometer to calibrate the eyepiece graticule

A

The eyepiece graticule remains constant no matter what magnification the cells are used at

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5
Q

What are the two types of objective lens in a compound light microscope

A

High power

Low power

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6
Q

What instrument was used before the first microscope

A

Magnifying glasses

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7
Q

What type of microscope did Robert Hooke invent

A

A compound light microscope

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8
Q

What is the main feature of compound microscopes

A

They have 2 types of lenses, the eyepiece and objective lenses

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9
Q

In what year was the electron microscope invented in

A

1931

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10
Q

What is an advantage of an electron microscope

A

Capable for far greater resolution and magnification of 1 mil.

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11
Q

What is a disadvantage of electron microscope

A

Living specimens are destroyed by high dose of radiation

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12
Q

Metric equivalent of decimetre, dm

A

1 x 10^-1 m

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13
Q

Metric equivalent of millimetre, mm

A

1 x 10^-3 m

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14
Q

Metric equivalent of micro metre

A

1 x 10^-6 m

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15
Q

Metric equivalent of nanometre, nm

A

1 x 10^-9 m

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16
Q

What does the amount of detail seen through a microscope depend on

A

The resolving power of the microscope

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17
Q

Resolving power

A

The smallest separation at which two separate objects can be distinguished (or resolved)

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18
Q

What is the resolving power of a microscope ultimately limited by

A

The wavelength of light

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19
Q

What is the wavelength of light

A

400-600nm

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20
Q

Why do some microscopes have blue filters

A

Blue has the shortest wavelength of visible light and to improve the resolving power a shorter wavelength of light is needed

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21
Q

Definition of magnification

A

How much bigger a sample appears to be under the microscope than it’s in real life

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22
Q

Definition of resolution

A

Ability to distinguish between two points on an image i.e. the amount of detail

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23
Q

What is the resolution of an image limited by and why

A

The wavelength of radiation used to view the sample
When objects in the specimen are smaller than half the wavelength of the radiation being used, they don’t interrupt the waves, and so aren’t detected

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24
Q

What is the wavelength of light much larger than

A

The wavelength of electrons, so the resolution of the light microscope is a lot lower

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25
Q

How does using a microscope with a more powerful magnification affect the resolution

A

It does not

It will increase the size of the image but objects closer than 200nm will still only be seen as one point

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26
Q

Compound microscopes

A

Use several lenses to obtain high magnification

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27
Q

Resolution of light microscopy

A

About 200nm, which is good enough to see cells, but not details of cell organelles

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28
Q

Examples of procedures undertaken to prepare slide samples

A 
Fixation 
Dehydration 
Embedding 
Sectioning
Staining 
Mounting
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29
Q

Light microscopy

A

Specimens are illuminated with light, which is focussed using glass lenses and viewed with the eye or photographic film.
Specimens can be living or dead, but often need to be stained with a coloured dye to make them visible

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30
Q

What is the wavelength of electrons

A

Less than 1nm, so can be used to resolve small sub-cellular ultra-structure

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31
Q

How did the electron microscope revolutionise biology

A

Allows organelles such as mitochondria, ER and membranes to be seen in detail for the first time

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32
Q

Problems with an electron microscope

A

Specimens must be fixed in plastic and viewed in a vacuum, and must therefore be dead
Specimens can be damaged by the electron beam
Specimens must be stained with an electron-dense chemical (usually heavy metals like osmium, lead or gold)

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33
Q

What are the two types of electron microscope

A

Transmission Electron Microscope (TEM)

Scanning Electron Microscope (SEM)

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34
Q

TEM

A

Works much like a light microscope, transmitting a beam of electrons through a thin specimen and then focusing the electrons to form an image on a screen or on film

Most common form of electron microscope and has best resolution

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35
Q

SEM

A

Scans a fine beam of electron onto a specimen and collects the electrons scattered by the surface

Has poorer resolution but gives excellent 3D images

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36
Q

Laser scanning confocal microscope

A

Used to observe an object at a certain depth within a cell

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37
Q

Why do we stain samples

A

To ensure contrast between structures

Identification of cells

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38
Q

Magnification of light microscope

A

X1500

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39
Q

Magnification of TEM

A

X500,000

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40
Q

Resolution of TEM

A

0.2 nm

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41
Q

Magnification of SEM

A

X100,000

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42
Q

Resolution of SEM

A

10nm

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43
Q

Method of laser scanning confocal microscopy

A

Using a laser light to scan an object point by point and a computer assembles the image

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44
Q

Pros of laser scanning confocal microscopy

A

Can be used to study whole, live specimens and can be used to obtain images at different depths in thick sections

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45
Q

Main stains

A

Haemoxylin

Eosin

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46
Q

Haemoxylin

A

Blue colour
Stains DNA and RNA in all nuclei
Often used together (differential staining)

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47
Q

Eosin

A

Pink or red colour

Stains connective tissue and substances in cytoplasm

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48
Q

IAM Equation

A

I
A M

I - image size
A - actual size
M - magnification

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49
Q

Eukaryotic Cells

A

Have a nucleus containing genetic info

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50
Q

Prokaryotic cells

A

Don’t have a nucleus

No membrane bound organelles

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51
Q

Organelles

A

Components of a cell, each with a different function

52
Q

Membrane bound

A

Surrounded by a membrane

53
Q

Structure of a nucleus

A 
Double nuclear envelope 
Nuclear pores 
Nucleoli 
Membrane of nuclear envelope continuous with rough ER membranes  
Nucleoplasm containing chromatins
54
Q

Function of nucleus

A

Contains genetic material (chromosomes)

Controls cell activities

55
Q

Function of double nuclear envelope

A

To enclose and protect DNA

56
Q

Function of nuclear pores

A

Allow entry of substances such as nucleotides for DNA replication and exit of molecules such as mRNA during protein synthesis

57
Q

Function of nucleoplasm containing chromatin

A

It is these, during cell division, condense to form chromosomes

58
Q

Function of the nucleoli

A

Assembles ribosomes, coenzymes, proteins and RNA

59
Q

Function of outer membrane of nuclear envelope being continuous with rough ER

A

Makes perinuclear space continuous with the lumen of the ER, thus allowing easy transport of substances

60
Q

Structure of mitochondrion

A

Double membrane
Inner membrane spanned by porins
Inner membrane folded to form cristae

61
Q

Function of double membrane in mitochondrion

A

Isolates reactions of the Kreb’s cycle. Compartmentalisation allows high conc. of enzymes and substrates to be maintained

62
Q

Function of innner membrane being folded in cristae

A

Increases the surface area for the attachment of enzymes

63
Q

Roles of cytoskeleton

A

Allow organelle movement
Give support and mechanical strength
Keep the cell’s shape stable

64
Q

Organelles in animal cells

A 
Vesicles 
Lysosomes 
Nucleolus
Golgi apparatus
Mitochondrion 
Rough ER
Smooth ER
Centriole 
Cell membrane 
Cytoplasm 
Ribosome
65
Q

Organelles in plant cells

A 
Cell wall 
Cell membrane 
Golgi apparatus 
Chloroplast 
Amyloplast 
Vacuole
Cytoplasm 
Mitochondrion 
Ribosomes
Rough ER
Smooth ER 
Lamella
66
Q

DNA in eukaryotes

A

Linear

67
Q

DNA in prokaryotes

A

Circular

68
Q

DNA association in eukaryotes

A

Associated with proteins called histones

69
Q

DNA organisation in prokaryotes

A

Proteins fold and condense DNA

70
Q

Types of organelles in eukaryotes

A

Both membrane and non-membrane bound

71
Q

Types of organelles in prokaryotes

A

Only non-membrane bound

72
Q

Non-membrane bound organelles

A

Ribosomes
Centrioles
Cytoskeleton
Cell wall

73
Q

Cell walls in eukaryotes

A

Chitin in fungi
Cellulose in plants
Not present in animals

74
Q

Cell wall in prokaryotes

A

Peptidoglycan (bacteria)

75
Q

Ribosomes in eukaryotes

A

Larger (80 S)

76
Q

Ribosomes in prokaryotes

A

Smaller (70 S)

77
Q

Reproduction in eukaryotes

A

Asexual or sexual

78
Q

Reproduction in prokaryotes

A

Binary fission

79
Q

Cell types in eukaryotes

A

Unicellular and multicellular

80
Q

Cell type in prokaryotes

A

Unicellular

81
Q

Organelles involved in protein synthesis

A 
Nucleus 
Ribosomes
Rough ER 
Vesicles
Golgi apparatus
82
Q

Organelles indirectly involved with protein synthesis

A

Nucleus (chromatin, nucleolus (RNA))

Smooth ER

83
Q

First stage in protein synthesis

A

Proteins are synthesised on ribosomes bound to the RER (translation)

84
Q

Second stage in protein synthesis

A

Proteins pass into RER cisternae and packaged into transport vesicles

85
Q

Third stage in protein synthesis

A

Vesicles move towards Golgi apparatus via transport function of cytoskeleton, they fuse with the cis-face

86
Q

Fourth stage in protein synthesis

A

Proteins are structurally modified as they pass through the Golgi cisternae and they leave the Golgi through the trans face

87
Q

Fifth stage in protein synthesis

A

If the protein is to leave the cell (secreted), vesicles travel to cell surface membranes fuse with the membrane and the proteins are released

88
Q

Lysosomes

A

Specialised forms of vesicles that contain hydrolytic enzymes
Responsible for breaking down water materials in cells
Play important role in apoptosis

89
Q

Apoptosis

A

Programmed cell death

90
Q

Vesicles

A

Membranous sacs used for storage and transport inside the cells
Single membrane with fluid inside

91
Q

Cytoskeleton

A

Network of fibres necessary for shape and stability

92
Q

The components of the cytoskeleton

A

Microfilaments
Microtubules
Intermediate fibres

93
Q

Microfilaments

A

Contractile fibres from actin

Responsible for cell movement and contraction in cytokinesis

94
Q

Actin

A

A protein

95
Q

Cytokinesis

A

Process in which cytoplasm of a single eukaryotic cell forms 2 daughter cells

96
Q

Microtubules

A

Scaffold-like structure determines shape of cell
Tracks for movement for organelles (vesicles) around cell
Form spindle fibres

97
Q

What are microtubules made from

A

Polymerisation of globular tubulin

98
Q

Spindle fibres

A

Have a role in physical segregation of chromosomes

99
Q

Intermediate fibres

A

Give cells mechanical strength and help maintain integrity

100
Q

Roles of cytoskeleton

A

Holds organelles in place
Controls movement of organelles
Gives support and mechanical strength
Keep cell’s shape stable

101
Q

Centrioles

A

Component of the cytoskeleton composed of microtubules

102
Q

Centrosome

A

Formed from two associated centrioles

Involved in the assembly and organisation of spindle fibres in cell division

103
Q

Functions of flagella

A

Enable cells mobility

Used as sensory organelle detecting chemical changes in the cell’s environment

104
Q

Types of cilia

A

Mobile

Stationary

105
Q

Stationary cilia

A

Present on surface of cells

Important functions in sensory organs

106
Q

Mobile cilia

A

Beat in a rhythmic manner (creating current) –> cause movement of fluids/objects adjacent to cell

107
Q

Where is mobile cilia found

A

In the trachea

In the fallopian tubes

108
Q

Cisternae

A

Fluid filled cavities that form transport channels

109
Q

What is the smooth ER responsible for

A

Lipid and carbohydrate synthesis, transport and storage

110
Q

What is the rough ER responsible for

A

Synthesis and transport of proteins

It’s an intracellular transport system

111
Q

Structure of Golgi apparatus

A

Stack of cisternae

Secretory vesicles bring materials to and fro

112
Q

Function of Golgi apparatus

A

Modifying proteins to make glycoproteins, lipoproteins or fold them into a 3D shape

113
Q

Structure of chloroplasts

A

Double membrane
Thylakoids containing chlorophyll
Stroma

114
Q

Granum

A

Each stack of thylakoids

115
Q

Why do chloroplasts have a double membrane

A

Protection

116
Q

Stroma

A

Fluid filled matrix in chloroplast

117
Q

Vacuole

A

Filled with water and solutes

Maintains cell’s stability

118
Q

How do vacuoles maintain cells’ stability

A

When the vacuole is full it pushes against the cell wall, making the cell turgid

119
Q

Where are ribosomes made

A

In the nucleolus, as 2 separate subunits, which pass through the nuclear envelope into the cell cytoplasm and then combine

Some attach to the RER

120
Q

What is the plant cell wall made from

A

Bundles of cell fibres

121
Q

Function of plant cell walls

A

Provide strength and support
Maintains cell’s shape
Contribute to the strength and support of whole plant
Allow solutions (solute and solution) to pass through

122
Q

Preparing a microscope slide - dry mount

A

Used for hairs, flowers, pollen etc
Sharp blade - individual cells are visible
Cut a thin slice - so light can pass through
Use tweezers to place your specimen onto your clean microscopic slide
Place a cover slip on top - making sure to not get fingerprints on it

123
Q

Preparing a microscope slide - wet mount (prevents dehydration)

A

Use for liquid specimens e.g. blood smears and plant cells
Pipette water onto your slide
Add specimen to middle of slide using tweezers
Carefully tilt cover slip next to water droplet - ensure no air bubbles, obstructs view of specimen
Once slip is in position, add stain next to edge - will get drawn under slip across specimen

124
Q

Role of membranes within cells

A

Compartamentalisation

Attachment site for enzymes

125
Q

How does the cytoskeleton move organelles around

A

Shortening or lengthening microtubule

Motor proteins

126
Q

Negative staining

A

Dyes such as Congo red are negatively charged and repel other negatively charged substances e.g. cytosol so will stay out of the cell

127
Q

What is the cytoplasm made of

A

Cytosol - water, salts and organic molecules

OCR A level Biology (25 decks)

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