2A Cell Structure and Division Flashcards
1
Q
What is the formula for magnification?
A
Magnification = image size/actual size
2
Q
Convert 4 mm to um
A
4000um
3
Q
What is magnification?
What is it controlled by?
A
- By how much an image is enlarged under a microscope
- The power of the lenses used
4
Q
What is resolution?
What is it controlled by?
A
- The minimum distance between two objects at which a microscope can distinguish them as separate entities
- The wavelength of the illumination used
5
Q
What are the 3 types of microscope?
A
Light microscope, TEM (Transmission Electron Microscope) and SEM (Scanning Electron Microscope)
6
Q
Which type of microscope is the strongest?
A
TEM
7
Q
Which type of microscope can you see colour?
A
Light microscope
8
Q
Which type of microscope can you see 3D images with?
A
SEM
9
Q
What can potentially be created with a TEM or SEM?
A
An artefact (a dust particle or air bubble)
10
Q
What can we use to measure the size of an object?
A
An eyepiece graticule
11
Q
What are the 3 stages of cell fractionation?
A
- Keep cells in a cold, buffered isotonic solution
- -> 1 Homogenisation
- -> 2 Filtered
- -> 3 Ultracentrifugation
12
Q
What happens in homogenisation (Stage 1)?
A
- Cells are broken up by a homogeniser (blender) to release the organelles by breaking up the plasma membrane
13
Q
What happens in Filtration (Stage 2)?
A
- The blended solution is filtered to remove any large tissue
14
Q
What happens in Ultracentrifugation (Stage 3)?
A
- filtrate placed in centrifuge + spun at a slow speed, heaviest organelles e.g. nuclei sink to the bottom and form a small pellet
- Fluid at the top is removed (supernatant)
- The supernatant is respun at a faster speed to gain the smaller organelles, this is repeated
15
Q
Who discovered the first cells?
A
Robert Hooke in 1665
16
Q
When were the first electron microscopes discovered?
A
- Developed in the 1930s
- Allowed scientists to see their ‘ultrastructure
17
Q
What are the components of the nucleus?
A
- Nuclear envelope
- Nuclear pores
- Nucleoplasm
- Chromosomes
- Nucleolus
18
Q
What is the function of the nuclear envelope?
A
- It surrounds the nucleus and encases it
- Made from a 2 lipid bilayer
19
Q
What is the function of the nuclear pores?
A
- Transports molecules across the nuclear envelope
- i.e. RNA moving out, proteins moving in
20
Q
What is the function of the nucleoplasm?
A
- It is the substance in a cell’s nucleus
- Contains the chromosomes and nucleolus
21
Q
What is the function of chromosomes?
A
- They carry genetic info
- Made of DNA and proteins
22
Q
What is the function of the nucleolus?
A
- Makes ribosomes
- Largest structure in nucleus
23
Q
What are the components in the mitochondria?
A
- Double membrane
- Cristae
- Matrix
24
Q
What is the double membrane (mitochondria)
A
- Outer membrane covers like a skin
- Inner membrane folded into layered structures
- Inner membrane increases SA
25
What is the cristae (mitochondria)?
- Folds made by inner membrane
| - More space for chemical reactions to take place
26
What is the matrix (mitochondria)?
- Fluid contained within the mitochondria
- Own ribosomes and DNA floating in it
- Contains granules which help with ion concentrations
27
What are the parts of a chloroplast?
- Chloroplast envelope
- Grana
- Stroma
28
What is the Chloroplast envelope (membrane)?
- Similar to structure of mitochondrial double membrane
29
What is the Grana?
- Stack of disks known as thylakoids
- Resembles a stack of coins
- Site of light dependant reactions of photosynthesis
- Connected by intergranal thylakoids
30
What is the Stroma
- Colourless fluid surrounding grana
- Contains enzymes required for photosynthesis
- DNA and ribosomes also present
31
What are the two types of Endoplasmic reticulum?
- Rough endoplasmic reticulum
| - Smooth endoplasmic reticulum
32
What is the rough endoplasmic reticulum?
Folds and processes proteins that have been made at the ribosomes
33
What is the smooth endoplasmic reticulum?
No ribosomes, lipid synthesis
34
What is the golgi apparatus?
- Where things are packaged into vesicles and move out of the cell
- For packaging and processes new lipids and proteins
- Makes lysosomes
35
What are lysosomes?
- Made in the golgi apparatus
- Allow destruction of unneeded parts in the cell
- Strong enzymes to help destruction
36
What 3 ways do cells differ?
- Function
- Shape
- Number/type of organelles
37
What are the levels of organisation?
- Specialised cell
- Tissue
- Organ
- System
- Organism
38
What are the features of a prokaryotic cell?
- No nucleus --> DNA strands and plasmid rings
- No membrane bound organelles
- Ribosomes are smaller than ones in eukaryotes - 70s
- 3 layer membrane; cell membrane, cell wall + capsule
- Flagellum + pili attached
39
What does the capsule of a prokaryotic cell do?
It stops chemical attacks
40
What is a virus like?
- Not a cell
| - Non-living
41
What are the parts of a virus cell?
- Nucleoproteins
- Matrix
- Capsid
- Genetic material (DNA) (RNA)
- Lipid envelope
- Attachment proteins
42
What are attachment proteins?
Bind to receptor proteins on the host cell
43
What is the lipid envelopes role?
Derived to host cell membrane
44
What is DNA/RNA
Encodes virus proteins
45
What is a capsid?
Protein coat that encapsulates the DNA/RNA
46
What are nucleoproteins?
Accessory proteins the virus needs e.g. enzyme
47
What is the matrix (virus)?
Protein layer on the inside of the envelope
48
Your beautiful x
not
49
Do all cells have the ability to divide?
All do, some lose this ability
50
How many times do specialised cells go through the cell cycle?
Once
51
What sort of cells does mitosis produce?
Body cells
52
What sort of cell does meiosis produce?
Gametes
53
What is the purpose of mitosis?
- Growth of tissues
- Replacement of lost cells
- Repair of damaged tissue
- Asexual reproduction
- Clones of T and B lymphocytes
- Abnormally divide to form tumors
54
What are the parts of a homologous chromosome?
- Chromatin --> two arms of an x shaped chromosome
| - Centromere --> the middle
55
What is chromatin?
DNA when it is not wound up tightly as a chromosome
56
What is a chromosome?
Compacts X or Y shaped form of chromatin formed during cell division
57
What are chromatids?
Two identical arms of an X shaped chromosome
58
What is the centromere?
The point at which the chromatids join
59
What is a homologous chromosome?
Two chromosomes originating from one parent, containing the same genes, but different alleles
60
When does most of the cell cycle take place?
In the interphase
61
What are the 6 phases in the cell cycle?
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
62
What happens in Interphase?
- -> Cell grows + DNA replicates
- -> Chromosomes not visible
- -> Not strictly part of mitosis
63
What happens in Prophase?
- -> Chromosomes condense + become visible
- -> Centrioles move to opposite ends of the cell
- -> Spindle apparatus forms from spindle fibres at the centrioles
64
What happens in the Metaphase?
- -> Nuclear envelope breaks down
| - -> Chromosomes align along the equator of the cell pulled by spindle apparatus
65
What happens in the Anaphase?
- -> Centromeres split, allowing chromatids to separate
| - -> Chromatids move towards poles, pulled by the spindle fibers
66
What happens in the Telophase?
- -> Spindle fibres disperse
- -> Nuclear envelope reforms
- -> Chromosomes decondense
67
What happens in Cytokinesis?
- -> A ring of protein filaments form around the equator of the cell
- -> It tightens and the cell splits into 2 cells
68
How are each of the checkpoints in the cell regulated?
With control genes
69
How are tumors created?
Mutated control genes cause cells to divide uncontrollably
70
What are the risk factors for tumors?
- Smoking
- Diet
- Obesity
- Physical activity
- Sunlight
71
What are the two types of tumor?
Benign and Malignant
72
What is a Benign tumor like?
Non-cancerous and doesn't spread
73
What are Malignant tumors like?
Fast growing, often spread and are classed as cancer
74
What are the treatments for cancer?
- Surgery
- Radiotherapy
- Chemotherapy
75
What does surgery (tumors) do?
Removes the tumor (usually benign)
76
What does radiotherapy do?
The radiation damages the DNA in cells (usually malignant)
77
What does chemotherapy do?
- Blocks enzymes in DNA synthesis
- Prevents DNA unwinding
- Inhibits synthesis of new nucleotides
- Prevents development of the spindle
78
How do you focus a SEM (microscope)?
Using a condenser electromagnet
79
What does the specimen for a SEM (microscope) need to be like?
- Doesn't have to be thin
- Cannot be living
- Must be in a vacuum
80
What may be created when using a SEM or TEM (microscope)?
An artefact (a dust particle or bubble)
81
What sort of image is produced using a SEM (microscope) ?
- No colour (can add false colour)
| - 3D image using computer analysis
82
What is a negative about SEM (microscope)?
- Can produce an artefact
| - Has a complicated prep
83
What does transmission mean (TEM)?
electrons go through specimen
84
What does scanning mean (SEM)?
scans surface
85
What sort of image is produced using a TEM (microscope)?
- 2D image
| - no colour (can add false colour)
86
How does a TEM (microscope) focus?
a condenser magnet
87
What are the limitations of a TEM (microscope)?
- cannot look at living things
- has to be in a vacuum
- must be a thin specimen
- complicated prep
- may produce an artefact
- no colour image
88
How do viruses replicate?
Via taking over a host cell
89
What are the 5 stages of virus replication?
1. Viral contents release
2. Virus enters cell
3. Viral RNA enters nucleus
4. Viral mRNA makes viral proteins
5. New viral particles are released
90
What are spindle fibres?
Pull apart chromosomes during cell replication
91
What are the parts of a eukaryotic cell?
- Plasma membrane
- RER
- Nucleolus
- Nucleus
- SER
- Lysosome
- Ribosome
- Nuclear envelope
- Golgi apparatus
- Cytoplasm
- Mitochondrion
92
What are the parts of a plant cell?
- Plasma membrane
- Chloroplast
- RER
- Cell wall (plasmodesma)
- Mitochondria
- Golgi apparatus
- Vacuole
- SER
- Cytoplasm
- Nucleolus
- Nucleus
- Ribosome
- Cell wall
93
What are algal cells?
They're a lot like plant cells - they have all the same organelles, including a cell wall and chloroplasts
94
What are fungal cells like?
A lot like plant cells but with 2 key differences:
- Their cell walls are made of chitin, not cellulose
- They don't have chloroplasts (bc they don't photosynthesis)
95
What is the cell surface membrane?
It's made of mainly lipids and proteins
96
What is the nucleus like?
A large organelle surrounded by a nuclear envelope which contains many pores
The nucleus contains chromosomes and a nucleoluse
97
What's a mitochondria like?
Usually oval shaped
They have a double membrane - inner one is folded to form structures called cristae
Inside the matrix are enzymes involved in respiration
98
What is structure of the chloroplast?
Small flattened structure found in plant & algal cells
99
What sort of membrane do chloroplasts have?
Surrounded by a double membrane & also has membranes inside called thylakoid membranes
100
What happens when thylakoid membranes are stacked in chloroplasts?
These membranes are stacked up in some parts of the chloroplast to form grana
101
How are grana linked?
Grana are linked by together by lamellae
102
What are the lamellae in grana like?
Thin, flat pieces of thylakoid membrane
103
What is the golgi apparatus like?
A group of fluid-filled membrane-bound flattened sacs
Vesicale are often seen at the edge of the sacs
104
What is the golgi vesicle like?
A small fluid-filled sac in the cytoplasm
Surrounded by a membrane & produced by the golgi apparatus
105
What is the function of the golgi vesicle?
Stores lipids & proteins made by the Golgi apparatus and transports them out of the cell
106
What is a lysosome like?
A round organelle surrounded by a membrane - with no clear internal structure
It's a type of golgi vesicle
107
What are the enzymes in lysosomes called?
lysozymes
108
What are the 2 main parts of a ribosome?
Small subunit
| Large subunit
109
Where is a ribosome found in the cell?
Either floats free in the cytoplasm or is attached in the RER
110
What are ribosomes made up of?
Proteins and RNA - it's not surrounded by a membrane
111
What is the RER?
A system of membranes enclosing s fluid-filled space
Surface is covered with ribosomes
112
What is the cell wall made from in plants & algae?
Made mainly of the carbohydrate cellulose
113
What is the cell wall in fungi made of?
Chitin
114
What is cell sap made up of?
A weak solution of sugar and salts
115
What is the surrounding membrane of a vacuole called?
Tonoplast
116
What is the the role of the vacuole?
Helps to maintain pressure inside the cell & keep the cell rigid - this stops plants wilting
Also involved in the isolation of unwanted chemicals inside the cell
117
You're doing so well keep going haha
Don't stop you will fail otherwise
Hope ur having fun :))))))))
"Don't know the solution until there's a problem" - Daniel Digges (29/09/20)
118
What is the magnification equation?
Magnification=size of image/size of real object
119
What is magnification definition?
How much bigger the image is than the specimen.
120
What is resolutions definition?
Resolution is how detailed the image is.More specifically, it's how well a microscope distinguishes between two points that are close together.
121
What are the two types of microscope?
Optical (light) and electron
122
What are features of an optical microscope?
- They use light to form an image
- They have a maximum resolution of about 0.2 micrometres.This means you can't see organelles smaller than 0.2 micrometres like ribosomes and lysosome.You can see the nucleus though.
- The maximum useful magnification of an optical microscope is about x1500
123
What are features of an electron microscope?
- They use electrons to form an image
- They have a higher resolution than optical microscopes so give a more detailed image
- They have a maximum resolution of around 0.0002 micrometres.
- The maximum useful magnification of an electron microscope is about x1 500 000
124
What are the two types of electron microscopes?
Scanning or transmission
125
What is a limitation of transmission electron microscopes?
They can only be used on thick specimens
126
Why do some parts of the specimen look darker in transmission electron microscopes?
Because denser parts of the specimen absorb more electrons which makes them look darker on the image you end up with.
127
What do TEM's use to focus the beam of electrons?
Electromagnets which transmit beam of electrons through the specimen
128
Do TEM's have high or low resolution?
High resolution which helps them see the internal structure of organelles like chloroplasts.
129
What is a limitation of scanning electron microscopes?
They have lower resolution images than TEM's
130
Can SEM's be used on thick specimens?
yes unlike TEM's
131
What do the images you end up with from SEM's show?
They show the surface of the specimen.They can also show the 3-D shape.
132
How does a scanning electron microscope work?
SEM's scan a beam of electrons across the specimen.This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
133
How do you prepare a temporary mount of a specimen on a slide?
1-Start by pipetting a small drop of water onto the slide.Then use tweezers to place thin section of specimen on water drop.
2-Add a drop of a stain.Stains used to highlight objects in a cell
3-Finally,add the cover slip.To do this stand the slip upright on the slide then carefully tilt it to cover specimen.Try not to get any air bubbles under there
134
What does cell fractionation do?
Separate organelles
135
What are the three steps to cell fractionation?
- Homogenisation-breaking up the cells
- Filtration-Getting rid of big bits
- Ultracentrifugation-Separating the organelles
136
What is homogenisation?
-It is done by grinding the cells up or vibrating them.This breaks up the plasma membrane and release the organelles into the solution.The solution ice-cold to reduce enzyme activity.Solution should also be isotonic.A buffer solution should be added to maintain Ph.
137
What is filtration?
Homogenised solution is filtered through a gauze to separate any large cell debris or tissue debris.The organelles are much smaller than the tissue so they filter through
138
How many steps of ultracentrifugation are there?
2
139
Step 1 of ultracentrifugation?
Cell fragments poured into a tube
The tube is put into centrifuge & spun at a low speed
Heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge.
Form a pellet at the bottom
Rest of the organelles are suspended in fluid above sediment called the supernatant.
140
Step 2 of ultracentrifugation?
Supernatant is drained off, poured into another tube & spun in centrifuge at higher speed
This is repeated over and over again with the pellet at the bottom getting lighter and lighter.
141
Give an example of a prokaryotic cell?
Bacteria cell
142
What is the cytoplasm in a prokaryotic cell like?
- No membrane-bound organelles
| - Has ribosomes (small)
143
What is the structure of the flagellum like?
Long, hair-like structure
144
What does the flagellum do?
Rotates to make cell move
145
What is the DNA like in a prokaryotic cell?
- No nucleus, so floats free in cytoplasm
- Circular DNA (one long coiled up strand)
- Not attached to histones
146
What is the structure of plasmids?
Small loops of DNA
147
What do plasmids do?
Contain genes for antibiotic resistance
148
What does the capsule in the eukaryotic cell do?
Protect bacteria from being attacked by cells of the immune system
149
What is the capsule made of?
Slime
150
What does the plasma membrane do?
Controls movement of substances into and out of the cell
151
What polymer is the cell wall made of?
Murein
152
What does the cell wall do?
Supports cells and prevents from changing shape
153
Name the parts of a prokaryotic cell?
- cytoplasm
- flagellum
- plasmids
- cell wall
- capsule
- plasma membrane
- circular DNA
154
Are viruses smaller than bacteria?
yes
155
What do bacteria have that viruses don't?
- cytoplasm
- plasma membrane
- ribosomes
156
What is found on the surface of a to a virus?
Attachment protein
157
What is the protein coat around the core called in a virus?
Capsid
158
How do prokaryotic cell reproduce?
binary fission
159
What are the 4 stages of binary fission?
1 - circular DNA (once) and plasmids (multiple times) replicate
2 - cells grow and DNA loops move to opposite ends of the pole
3 - cytoplasm begins to divide (new cell walls form)
4 - cytoplasm divides and 2 daughter cells are produced, each having one copy of DNA and variable plasmids
