2.1.1 Cell Structure Flashcards
1
Q
Define magnification
A
How many times larger an image is than the actual object
2
Q
Define resolution
A
The degree to which it’s possible to distinguish between two objects that are very close together (higher resolution = greater detail)
3
Q
What is staining and why is it carried out
A
When you change the colour of a cell so you can see the sub cellular structures more clearly and increases visibility + contrst
4
Q
What is differential staining
A
When you stain a specimen with multiple dyes, allowing different tissues to show up which creates further contrast
5
Q
What is sectioning
A
When a specimen is embedded in wax which can then be thinly sliced without distorting the structure of the specimen (useful for soft tissue)
6
Q
What is fixing
A
Using chemicals to prepare a sample for electron microscopy
7
Q
How do you figure out magnification (lens)
A
Magnification = eyepiece lens x objective lens
8
Q
How do you figure out magnification (image)
A
Magnification = image / object
9
Q
Name as many parts of the ultrastructure of a plant cell
A
- cytoplasm
- cell surface/plasma membrane
- cell wall
- chloroplast
- vacuole
- mitochondrion
- ribosomes
- nucleolus
- nuclear envelope
- Golgi apparatus
- smooth endoplasmic reticulum
- rough endoplasmic reticulum
- amyloplast containing starch
10
Q
What is the structure of Nucleus
A
- surrounded by double membrane called nuclear envelope with pores
- continuous with endoplasmic reticulum
11
Q
What is the function of the nucleus
A
- contains DNA carrying information for protein synthesis
- chromatin is the genetic material, consisting of DNA wound around histone proteins
- when cell is about to divide, chromatin coils and condenses to form structures called chromosomes
12
Q
What is the structure of the nucleolus
A
- has no membrane around it + contains RNA
- found inside the nucleus
13
Q
What is the function of the nucleolus
A
- makes RNA + ribosomes which pass into the cytoplasm
> this happens when the outer and inner membranes of the nucleus fuse together allowing dissolved substances to pass through
14
Q
What is the structure of the RER
A
- system of membranes containing fluid filled cavities (cisternae) which are continuous with nuclear membrane
- contains ribosomes on surface
15
Q
What is the structure of the SER
A
- system of membranes containing fluid filled cavities (cisternae) which are continuous with nuclear membrane
- no ribosomes
16
Q
What is the structure of the Golgi Apparatus
A
- stack of membrane-bound flattened sacs (cisternae)
- secretary vesicles bring materials to + from the Golgi apparatus
17
Q
What is the function of the Golgi Apparatus
A
- modifies and packages cell products (proteins)
- encloses substances in vesicles to be secreted
> secretory vesicles leave cells + lysosomes stay in the cell
18
Q
What is the structure of Mitochondria
A
- 2-5 micro - metres long
- surrounded by 2 membranes with a fluid filled space
- inner membrane folded into cristae
19
Q
What is the function of Mitochondria
A
- site of aerobic respiration - where ATP is produced
- lots of mitochondria found in active cells where metabolic activity is higher
20
Q
What is the structure of Vacuole
A
- surrounded by membrane called tonoplast (partially permeable) + contains fluid
21
Q
What is the function of Vacuole
A
- plant cells have large permanent vacuole
- filled with water + solutes which maintain cell stability by making cell turgid when it pushes against the cell wall
> if plant cells are all turgid, it helps support the plant
22
Q
What is the structure of chloroplasts
A
- large, 4-10 micro metres
- surrounded by double membrane / envelope
- inner membrane has stacks of flattened membrane sacks called thylakoids
> a stack of thylakoids = a granum - fluid filled matrix is called stroma
- contains loops of DNA and starch grains
23
Q
What is the function of chloroplasts
A
- site of photosynthesis
> 1st stage occurs in grana
> 2nd stage occurs in stroma - chlorophyll molecules found on thylakoid membranes
24
Q
What is the structure of Lysosomes
A
- vesicles (bags) formed from golgi apparatus containing digestive enzymes (hydrolytic enzymes) to break down materials
- surrounded by single membrane
- abundant in white blood cells that break down microorganisms
25
What is the function of Lysosomes
- keep the powerful hydrolytic enzymes separate from rest of the cell
- can engulf old cell organelles + foreign matter
- responsible for breaking down pathogens ingested by phagocytic cells
26
What is the structure of Ribosomes
- small spherical organelles, 20 nm
- made of ribosomal RNA in nucleolus
- free floating in cytoplasm or attached to ER, forming rough ER
- no membrane + is the site of protein synthesis
27
What is the function of Ribosomes
- ribosomes on RER mainly synthesis proteins that will be exported outside cell
- ribosomes free floating are site of assembly of proteins that will be used inside the cell
28
What is the structure of Centrioles
- consist of 2 tubes of microtubules
- microtubules made of tubulin protein subunits and then arranged to form a cylinder
- pair found next to nucleus in animal cells
29
What is the function of Centrioles
- aid cell division: move to opposite poles of the cell as spindle develops
- spindle, made from threads of tubulin, forms from centrioles
30
What is the structure of Cilia + undulipodia
- protrusions from the cell + surrounded by cell surface membrane
- each contains microtubules
- formed from centrioles
> centrioles multiply + line up beneath cell surface membrane > microtubules sprout outwards from each centriole forming cilia or undulipodia
31
What is the function of Cilia + undulipodia
- epithelial cells lining airways have many cilia that move the mucus
- nearly all cells have at least one cilium that acts as an antenna and contains receptors allowing cell to detect signals about its immediate environment
- undulipodia = longer cilium
32
What is the structure of Cellulose cell wall
- cellulose cell wall of plants is on the outside of the plasma membrane
- made from bundles of cellulose fibres, a complex carbohydrate
33
What is the function of Cellulose cell wall
- strong + can prevent plant cells from bursting when turgid
- provides:
> strength and support
> maintains cells shape
> permeable + allow solutions (solutes + solvents) to pass through
- fungi have cell walls containing chitin, not cellulose
34
What is the structure of cytoskeleton + what it consists of
- present throughout cytoplasm of all eukaryotic cells
- network of fibres necessary for the shape + stability of a cell
- it consists of:
> rod-like microfilaments made of subunits of protein actin (7nm)
> intermediate filaments (10nm)
> straight, cylindrical microtubules, made of protein subunits called tubulin (18-30nm)
35
What is the function of microfilaments
- cell movement, cell contraction during cytokinesis
-support + mechanical strength + keep cells shape stable
36
What is the function of microtubules
- polymerise to form tubes that form scaffold like structure that determines the shape of a cell
- act as tracks for movement of organelles around cells (incl vesicles)
- microtubules form spindles that allow chromosomes to be separated in cell division
37
What is the function of intermediate fibres
- anchor the nucleus within the cytoplasm
-give mechanical strength to cells and help maintain their integrity
38
What is the radiation used for light microscope
Light rays
39
What is the radiation used for electron microscope
Electron beams
40
What do light microscopes focus with
Lenses
41
What do electron microscopes focus with
Magnets
42
What is the magnification for light microscopes
X1500
43
What is the magnification for electron microscope
X500,000
44
What is the resolving power for light microscope
200nm
45
What is the resolving power for electron microscope
0.2nm
46
What state does the biological matter have to be for light microscope
Living or dead
47
What state does the biological matter have to be for electron microscope
Dead
48
What is the size of light microscope
Small and portable
49
What is the size of electron microscope
Very large and static
50
What is the ease of use for light microscope
Easy to use
51
What is the ease of use for electron microscopes
Skill and training required
52
What is the cost of light microscope
Relatively cheap
53
What is the cost of electron microscope
Very expensive
54
Does the sample have to be in a vacuum for light microscope
No
55
Does the sample have to be in a vacuum for electron microscope
- yes
> because if not the electrons could bounce off air particles etc
56
Does the image in light microscope have colour
Yes
57
Does the image in electron microscope have colour
Black + white
58
What are the 2 types of electron microscopes
- Transmission electron microscope (TEM)
- Scanning electron microscope (SEM)
59
What happens to the electron beams in TEM
- beams of electrons pass through the very thin sample
60
What happens to the electron beams in SEM
Electron beams are directed onto the sample
61
How do the electrons produce an image in TEM
Electrons pass through denser parts more easily which creates contrast in the image
62
How do the electrons produce an image in SEM
Electrons bounce off sample and become focused on the screen
63
What is the type of image produced in TEM
2D
64
What is the type of image produced in SEM
3D
65
What is the magnification of TEM
X 500,000
66
What is the magnification of SEM
X 200,000
67
In TEM what has to happen to the specimen before being used
- it has to be chemically fixed by being dehydrated and stained with metal salts
68
What do confocal microscopes allow you to do
- observe whole living specimens and can focus on structures at different depths within a specimen
69
How do confocal microscopes work
- the laser light scans the object point by point and assembles it by the computer putting the pixel information into one image
70
What is an advantage of confocal microscopes
- image is high in resolution and shows high contrast
71
What is an advantage of confocal microscopes
- image is high in resolution and shows high contrast
72
what is the cytoskeleton
- a series of protein threads of 2 main types:
> microtubules (tubular)
>microfilaments (solid strands)
73
what are the functions of the cytoskeleton
- cellular movement (cilia and flagella)
- forms 'tracks' inside cells for organelles to move along e.g. vesicles
- strength and support - 'scaffolding' to keep cell's shape and strengthen it
74
what is the centriole made of
microtubules made of tubulin protein
75
what is flagella made of
microtubules (eukaryotic only)
76
what are cilia made of
microtubules
77
what is the function of the centriole
- 2 associated centrioles form the centrosome which is involved in the assembly and organisation of the spindle fibres during cell division
- also position structures such as cilia and flagella
78
what is the function of the flagella
- enables cell mobility
- in some cells they're used as sensory organelle detecting chemical changes in cell's environment
79
what is the function of the cilia
- stationary cilia present on surface of many cells + have many important functions in sensory organs e.g. nose
- mobile cilia beat in rythmatic manner, creating current and causes fluids or objects adjacent to cell to move
> e.g. remove mucous from airways
80
what is the structure of centriole
- hollow bundles of fibres
> bundles made of triplets of microtubules
81
what is the structure of flagella + cilia
- ring of 9 pairs of microtubules surrounding 2 central ones
82
where are centrioles found
within the nucleus
83
where are flagella found
on surface of cells (eukaryotic + prokaryotic)
84
where are cilia found
protrudes from cells outside of ciliated epithelial cells
85
how many centrioles are found
in pairs
86
how many flagella are found
one (sperm cells)
87
how many cilia are found
many`
88
what is plant cell wall made of
- made of cellulose microfibrils (cellulose molecules in bundles) embedded in layer of pectins (adhesive) and hemicellulose
89
how are cells in plant cell wall connected
- calcium pectate cements the cells next to each other
90
what is the function of plant cell wall
- provides support for the cell
- allows many substances to be imported / exported
91
what may plant cell wall contain between cells which allows for movement of water and solutes
- plasmodesmata - cytoplasmic link between cells
92
what do vesicles use to move around the cell
- motor proteins + cytoskeleton
93
what is exocytosis
- when a vesicle fuses with the cell's surface membrane to release substances out of the cell membrane
94
what is endocytosis
- when a substance is engulfed by the cell's surface membrane and packaged into a vesicle
95
describe how some organelles work together to synthesis and secrete a protein
- nucleus contains DNA and so template strand mRNA is made and leaves nucleus through pores
- mRNA attaches to ribosomes on RER and translation occurs producing chain of amino acids
- amino acids continue along RER until it's packaged into transport vesicle
- transport vesicle moves along cell by motor proteins on cytoplasm to the Golgi apparatus
- at the Golgi apparatus protein is modified and packaged into secretory vesicle which leaves and goes to cell surface membrane
- exocytosis takes place as vesicle fuses with cell's surface membrane and releases the protein
96
compare the cell sizes of prokaryotes and eukaryotes
- prokaryotes = small (1-10 micrometers)
- eukaryotes = larger (10-150 micrometers)
97
describe the genetic material in prokaryotes
- free DNA not wound around histone proteins + floats free in cytoplasm as a loop
- small loops of DNA called plasmids
- nucleoid / circular chromosome
98
describe the genetic material in eukaryotes
- DNA contained in nucleus
- true nucleus
- linear chromosome
99
compare the ribosome size of prokaryotes and eukaryotes
- prokaryotes = smaller (70s)
- eukaryotes = larger (80s)
100
whare is the respiration location in prokaryotes vs eukaryotes
- prokaryotes = mesosomes
- eukaryotes = mitochondria
101
describe the flagella found in prokaryotes vs eukarotes
- prokaryotes = simple, no microtubules (20nm)
- eukaryotes = complex, microtubules (200nm)
102
where does photosynthesis take place in prokaryotes vs eukaryotes
- prokaryotes = may take place on unstacked membranes
- eukaryotes = chloroplasts
103
give examples of prokaryotes + eukaryotes
- prokaryotes = bacteria
- eukaryotes = plant, animal, fungi
104
how are mitochondria and chloroplast similar to prokaryotic cells
- have their own membrane, DNA and replicate independantly
105
what is the Endosymbiont theory
- theory states that initially mitochondria and chloroplasts were prokaryotic cells that were engulfed by larger cells but not digested
- this began a symbiont (mutually exclusive) relationship between the 2 cells, larger cell provided mitochondria with protection and nutrients and mitochondria carried out respiration providing larger cell with more energy
106
What is the function of RER
- synthesis + transport of proteins
- large surface area for ribosomes to assemble amino acids into proteins
- cisternae forms channels for transporting substances from one area of a cell to another
107
What is the function of SER
- involved with absorption, synthesis and transport of lipids + steroids
- contains enzymes that catalyse reactions involved with lipid metabolism
