2.1.1 - Cell Structure Flashcards
1
Q
What does a microscope allow us to do
A
Magnify an object many times
2
Q
Eyepiece graticule
A
Circular disk that fits onto the eyepiece and contains a tiny ruler with equal divisions on it
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
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
5
Q
What are the two types of objective lens in a compound light microscope
A
High power
Low power
6
Q
What instrument was used before the first microscope
A
Magnifying glasses
7
Q
What type of microscope did Robert Hooke invent
A
A compound light microscope
8
Q
What is the main feature of compound microscopes
A
They have 2 types of lenses, the eyepiece and objective lenses
9
Q
In what year was the electron microscope invented in
A
1931
10
Q
What is an advantage of an electron microscope
A
Capable for far greater resolution and magnification of 1 mil.
11
Q
What is a disadvantage of electron microscope
A
Living specimens are destroyed by high dose of radiation
12
Q
Metric equivalent of decimetre, dm
A
1 x 10^-1 m
13
Q
Metric equivalent of millimetre, mm
A
1 x 10^-3 m
14
Q
Metric equivalent of micro metre
A
1 x 10^-6 m
15
Q
Metric equivalent of nanometre, nm
A
1 x 10^-9 m
16
Q
What does the amount of detail seen through a microscope depend on
A
The resolving power of the microscope
17
Q
Resolving power
A
The smallest separation at which two separate objects can be distinguished (or resolved)
18
Q
What is the resolving power of a microscope ultimately limited by
A
The wavelength of light
19
Q
What is the wavelength of light
A
400-600nm
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
21
Q
Definition of magnification
A
How much bigger a sample appears to be under the microscope than it’s in real life
22
Q
Definition of resolution
A
Ability to distinguish between two points on an image i.e. the amount of detail
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
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
25
How does using a microscope with a more powerful magnification affect the resolution
It does not
| It will increase the size of the image but objects closer than 200nm will still only be seen as one point
26
Compound microscopes
Use several lenses to obtain high magnification
27
Resolution of light microscopy
About 200nm, which is good enough to see cells, but not details of cell organelles
28
Examples of procedures undertaken to prepare slide samples
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Fixation
Dehydration
Embedding
Sectioning
Staining
Mounting
```
29
Light microscopy
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
30
What is the wavelength of electrons
Less than 1nm, so can be used to resolve small sub-cellular ultra-structure
31
How did the electron microscope revolutionise biology
Allows organelles such as mitochondria, ER and membranes to be seen in detail for the first time
32
Problems with an electron microscope
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)
33
What are the two types of electron microscope
Transmission Electron Microscope (TEM)
| Scanning Electron Microscope (SEM)
34
TEM
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
35
SEM
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
36
Laser scanning confocal microscope
Used to observe an object at a certain depth within a cell
37
Why do we stain samples
To ensure contrast between structures
| Identification of cells
38
Magnification of light microscope
X1500
39
Magnification of TEM
X500,000
40
Resolution of TEM
0.2 nm
41
Magnification of SEM
X100,000
42
Resolution of SEM
10nm
43
Method of laser scanning confocal microscopy
Using a laser light to scan an object point by point and a computer assembles the image
44
Pros of laser scanning confocal microscopy
Can be used to study whole, live specimens and can be used to obtain images at different depths in thick sections
45
Main stains
Haemoxylin
| Eosin
46
Haemoxylin
Blue colour
Stains DNA and RNA in all nuclei
Often used together (differential staining)
47
Eosin
Pink or red colour
| Stains connective tissue and substances in cytoplasm
48
IAM Equation
I
A M
I - image size
A - actual size
M - magnification
49
Eukaryotic Cells
Have a nucleus containing genetic info
50
Prokaryotic cells
Don’t have a nucleus
| No membrane bound organelles
51
Organelles
Components of a cell, each with a different function
52
Membrane bound
Surrounded by a membrane
53
Structure of a nucleus
```
Double nuclear envelope
Nuclear pores
Nucleoli
Membrane of nuclear envelope continuous with rough ER membranes
Nucleoplasm containing chromatins
```
54
Function of nucleus
Contains genetic material (chromosomes)
| Controls cell activities
55
Function of double nuclear envelope
To enclose and protect DNA
56
Function of nuclear pores
Allow entry of substances such as nucleotides for DNA replication and exit of molecules such as mRNA during protein synthesis
57
Function of nucleoplasm containing chromatin
It is these, during cell division, condense to form chromosomes
58
Function of the nucleoli
Assembles ribosomes, coenzymes, proteins and RNA
59
Function of outer membrane of nuclear envelope being continuous with rough ER
Makes perinuclear space continuous with the lumen of the ER, thus allowing easy transport of substances
60
Structure of mitochondrion
Double membrane
Inner membrane spanned by porins
Inner membrane folded to form cristae
61
Function of double membrane in mitochondrion
Isolates reactions of the Kreb’s cycle. Compartmentalisation allows high conc. of enzymes and substrates to be maintained
62
Function of innner membrane being folded in cristae
Increases the surface area for the attachment of enzymes
63
Roles of cytoskeleton
Allow organelle movement
Give support and mechanical strength
Keep the cell’s shape stable
64
Organelles in animal cells
```
Vesicles
Lysosomes
Nucleolus
Golgi apparatus
Mitochondrion
Rough ER
Smooth ER
Centriole
Cell membrane
Cytoplasm
Ribosome
```
65
Organelles in plant cells
```
Cell wall
Cell membrane
Golgi apparatus
Chloroplast
Amyloplast
Vacuole
Cytoplasm
Mitochondrion
Ribosomes
Rough ER
Smooth ER
Lamella
```
66
DNA in eukaryotes
Linear
67
DNA in prokaryotes
Circular
68
DNA association in eukaryotes
Associated with proteins called histones
69
DNA organisation in prokaryotes
Proteins fold and condense DNA
70
Types of organelles in eukaryotes
Both membrane and non-membrane bound
71
Types of organelles in prokaryotes
Only non-membrane bound
72
Non-membrane bound organelles
Ribosomes
Centrioles
Cytoskeleton
Cell wall
73
Cell walls in eukaryotes
Chitin in fungi
Cellulose in plants
Not present in animals
74
Cell wall in prokaryotes
Peptidoglycan (bacteria)
75
Ribosomes in eukaryotes
Larger (80 S)
76
Ribosomes in prokaryotes
Smaller (70 S)
77
Reproduction in eukaryotes
Asexual or sexual
78
Reproduction in prokaryotes
Binary fission
79
Cell types in eukaryotes
Unicellular and multicellular
80
Cell type in prokaryotes
Unicellular
81
Organelles involved in protein synthesis
```
Nucleus
Ribosomes
Rough ER
Vesicles
Golgi apparatus
```
82
Organelles indirectly involved with protein synthesis
Nucleus (chromatin, nucleolus (RNA))
| Smooth ER
83
First stage in protein synthesis
Proteins are synthesised on ribosomes bound to the RER (translation)
84
Second stage in protein synthesis
Proteins pass into RER cisternae and packaged into transport vesicles
85
Third stage in protein synthesis
Vesicles move towards Golgi apparatus via transport function of cytoskeleton, they fuse with the cis-face
86
Fourth stage in protein synthesis
Proteins are structurally modified as they pass through the Golgi cisternae and they leave the Golgi through the trans face
87
Fifth stage in protein synthesis
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
Lysosomes
Specialised forms of vesicles that contain hydrolytic enzymes
Responsible for breaking down water materials in cells
Play important role in apoptosis
89
Apoptosis
Programmed cell death
90
Vesicles
Membranous sacs used for storage and transport inside the cells
Single membrane with fluid inside
91
Cytoskeleton
Network of fibres necessary for shape and stability
92
The components of the cytoskeleton
Microfilaments
Microtubules
Intermediate fibres
93
Microfilaments
Contractile fibres from actin
| Responsible for cell movement and contraction in cytokinesis
94
Actin
A protein
95
Cytokinesis
Process in which cytoplasm of a single eukaryotic cell forms 2 daughter cells
96
Microtubules
Scaffold-like structure determines shape of cell
Tracks for movement for organelles (vesicles) around cell
Form spindle fibres
97
What are microtubules made from
Polymerisation of globular tubulin
98
Spindle fibres
Have a role in physical segregation of chromosomes
99
Intermediate fibres
Give cells mechanical strength and help maintain integrity
100
Roles of cytoskeleton
Holds organelles in place
Controls movement of organelles
Gives support and mechanical strength
Keep cell's shape stable
101
Centrioles
Component of the cytoskeleton composed of microtubules
102
Centrosome
Formed from two associated centrioles
| Involved in the assembly and organisation of spindle fibres in cell division
103
Functions of flagella
Enable cells mobility
| Used as sensory organelle detecting chemical changes in the cell's environment
104
Types of cilia
Mobile
| Stationary
105
Stationary cilia
Present on surface of cells
| Important functions in sensory organs
106
Mobile cilia
Beat in a rhythmic manner (creating current) --> cause movement of fluids/objects adjacent to cell
107
Where is mobile cilia found
In the trachea
| In the fallopian tubes
108
Cisternae
Fluid filled cavities that form transport channels
109
What is the smooth ER responsible for
Lipid and carbohydrate synthesis, transport and storage
110
What is the rough ER responsible for
Synthesis and transport of proteins
| It's an intracellular transport system
111
Structure of Golgi apparatus
Stack of cisternae
| Secretory vesicles bring materials to and fro
112
Function of Golgi apparatus
Modifying proteins to make glycoproteins, lipoproteins or fold them into a 3D shape
113
Structure of chloroplasts
Double membrane
Thylakoids containing chlorophyll
Stroma
114
Granum
Each stack of thylakoids
115
Why do chloroplasts have a double membrane
Protection
116
Stroma
Fluid filled matrix in chloroplast
117
Vacuole
Filled with water and solutes
| Maintains cell's stability
118
How do vacuoles maintain cells' stability
When the vacuole is full it pushes against the cell wall, making the cell turgid
119
Where are ribosomes made
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
What is the plant cell wall made from
Bundles of cell fibres
121
Function of plant cell walls
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
Preparing a microscope slide - dry mount
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
Preparing a microscope slide - wet mount (prevents dehydration)
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
Role of membranes within cells
Compartamentalisation
| Attachment site for enzymes
125
How does the cytoskeleton move organelles around
Shortening or lengthening microtubule
| Motor proteins
126
Negative staining
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
What is the cytoplasm made of
Cytosol - water, salts and organic molecules
