2A - Cell Structure And Division Flashcards
1
Q
What are the two types of cell?
A
- Prokaryotic
* Eukaryotic
2
Q
What are prokaryotic organisms made of?
A
Prokaryotic cells - if they are single-celled, they may BE prokaryotic cells.
3
Q
What are eukaryotic organisms made of?
A
Eukaryotic cells
4
Q
What are eukaryotic cells?
A
Larger, complex cells -> Found in advanced organisms such as animals
5
Q
What are prokaryotic cells?
A
Smaller, simpler cells -> Found in basic organisms, such as bacteria
6
Q
Which cell type is more basic?
A
Prokaryotic cells
7
Q
Give some examples of eukaryotic organisms.
A
- Animals
- Plants
- Algae
- Fungi
8
Q
Give some examples of prokaryotic cells.
A
• Bacteria
9
Q
What are organelles?
A
Parts of cells with specific functions.
10
Q
What are the organelles of an animal cell? (9)
A
- Plasma membrane
- Nucleus (+ Nucleolus + Nuclear envelope)
- Ribosome
- Mitochondria
- Cytoplasm
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Golgi apparatus
- Lysosome
11
Q
What are the organelles of a plant cell? (12)
A
- Plasma membrane
- Nucleus (+ Nucleolus + Nuclear envelope)
- Ribosome
- Mitochondria
- Cytoplasm
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Golgi apparatus
- Lysosome
- Chloroplast
- Cell wall (+ Plasmodesmata)
- Vacuole
12
Q
Remember to revise labelling an animal and plant cell.
A
Pg 24 of revision guide
13
Q
What are the extra features of plant cells compared to animal cells?
A
- Cellulose cell wall (with plasmodesmata)
- Vacuole
- Chloroplasts
14
Q
What might you also find in plant cells that is not an organelle?
A
Starch grains - these are just used for storage.
15
Q
What is the difference between plant and animal cells?
A
Plant cells have all the same organelles as animals cells as well as:
• Cellulose cell wall
• Vacuole
• Chloroplasts
16
Q
Are algae single-felled or multicellular?
A
They can be both.
17
Q
How do algal cells compare to plant cells?
A
They are very similar and have all the same organelles.
18
Q
How do fungal cells compared to plant cells?
A
They have all the same organelles as plant cells except:
• Cell wall is made of chitin, not cellulose
• Don’t have chloroplasts
19
Q
Do organelles have membranes?
A
Yes, mostly - this can make them easy to confuse with entire cells.
20
Q
Remember to revise labelling cell organelles.
A
Pg 25 of revision guide.
21
Q
What is the cell-surface membrane and what is it made of?
A
- Membrane found on the surface of animal cells and just inside the cell wall of other cells
- Mad of lipids and proteins
22
Q
What is the function of the cell surface membrane?
A
- Controls movement of substances in and out of cell
* Has receptor molecules to respond to chemicals (e.g. hormones)
23
Q
What are the parts of the nucleus?
A
- Nuclear envelope
- Nucleolus
- Chromatin
24
Q
What is the function of the nucleus?
A
- Control’s the cell’s activities
- Stores DNA which contains instructions for protein synthesis
- Nucleolus makes ribosomes
25
What is the nuclear envelope (and its pores) and what do they do?
* Double membrane which surrounds the nucleus
| * Pores control movement of substances between the nucleus and the cytoplasm
26
What is the nucleolus and what does it do?
* Found in the nucleus
| * Produces ribosomes (by producing ribosomal DNA and putting the ribosomes together)
27
What is chromatin and what does it do?
* The chromosomes found in the nucleus
| * DNA stories instructions to make proteins
28
What are chromosomes in the nucleus made from?
Protein-bound linear DNA
29
What are the parts of a mitochondrion?
* Inner membrane
* Outer membrane
* Cristae
* Matrix
30
What is the function of a mitochondrion?
• Site of aerobic respiration, where ATP is produced
31
What are cristae and what do they do?
* Folds in the inner membrane of mitochondria
| * They increase the surface area for the attachment of proteins and enzymes
32
What is the matrix and what does it do?
* The fluid in mitochondria which contains proteins, lipids, ribosomes and DNA
* This allows protein synthesis to happen
33
What is the function of the membranes of mitochondria?
They control what goes in and out of the mitochondrion
34
Do mitochondria produce proteins?
Yes, they make some of their own proteins, which is why they have small amounts of DNA inside.
35
What are the parts of a chloroplast?
* Two membranes
* Stroma
* Grana (stacks of thylakoid membranes)
* Lamellae
36
What is the function of a chloroplast?
• The site where photosynthesis happens
37
What does the double membrane in chloroplasts do?
* Collectively known as the chloroplast envelope
| * Control what goes in and out of the chloroplast
38
What is the stroma and what does it do?
* A fluid-filled area of a chloroplast
| * Some parts of photosynthesis happen here
39
What is a granum and what does it do?
* A stack of thylakoids membranes found in chloroplasts
| * First stage of photosynthesis happens here
40
What is a thylakoid membrane?
It is a part of the chloroplast. Many of these membranes can be stacked on top of each other to form a GRANUM. Intergranal lamella are also made from thylakoid membrane.
41
What is a lamella and what does it do?
• A thin piece of thylakoid membrane which links grana together in chloroplasts
42
What is the Golgi apparatus and what are its functions?
• Group of fluid-filled, membrane-bound flattened sacs
• Processes and packages new lipids and proteins
• Produces vesicles, including lysosomes
(• Produces secretory enzymes)
(• Secretes carbohydrates)
43
What produces vesicles?
The Golgi apparatus
44
What is the function of a vesicle?
* Stores lipids and proteins (made by the Golgi apparatus)
| * Transports these out of the cell (through the cell membrane)
45
What is a vesicle?
* A small, fluid-filled sac in the cytoplasm, surrounded by a membrane and made by the Golgi apparatus
* Used to stores proteins and lipids from the Golgi and transport these out of the cell
46
What is a lysosome?
• A type of Golgi vesicle which contains lysozymes to digest invading cells and break down old cell components
47
What is the function of a lysosome?
Contains lysozymes (digestive enzymes) to:
• Digest invading cells
• Break down old cell components
• Release enzymes outside of cell to destroy material
48
What is a lysozyme and where is it found?
* Digestive enzyme found in lysosomes.
| * Used to break down old cell components and digest invading cells.
49
Where are ribosomes found?
Either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum.
50
Which cell components have no membrane?
• Ribosomes
51
What are the parts of a ribosome?
* Large sub-unit
| * Small sub-unit
52
What is the function of a ribosome?
• The site where proteins are synthesised.
53
What is a ribosome made of?
Proteins and RNA
54
What is the relative size of a ribosome?
Very small
55
What are the different sites of synthesis and modification of proteins, carbohydrates and lipids?
* RER - Protein folding and processing (+ synthesis by ribosomes)
* SER - Lipid and carbohydrate synthesis and processing
* Golgi apparatus - Protein and lipid modification
56
What is the rough endoplasmic reticulum?
* System of membranes enclosing a fluid-filled space
| * Surface is covered with ribosomes
57
What is the function of the rough endoplasmic reticulum?
* Providing a large SA for ribosomes
* Folding and processing of proteins
* Pathway for transport of proteins around cell
58
What is the smooth endoplasmic reticulum?
* System of membrane enclosing a fluid-filled space
| * No ribosomes on the surface
59
What are the flattened sacs in the Golgi apparatus called?
Cisternae
60
What is the function of the smooth endoplasmic reticulum?
• Synthesis, storage and transport of lipids and carbohydrates
61
What is the function of the Golgi apparatus?
• Processes and packages new lipids and proteins
• Produces vesicles, including lysosomes
(• Produces secretory enzymes)
(• Secretes carbohydrates)
62
Describe the process and organelles involved in creating different proteins, lipids and carbohydrates.
Lipids and carbohydrates are synthesised in the SER. The SER modifies these and transports them. Proteins are synthesised by ribosomes (on the RER). The RER processes and transports them.
The Golgi apparatus then modifies these. This includes creating glycoproteins (carbohydrates added to proteins) and secretory enzymes (like those in the pancreas). Finally, these products are transported away using the Golgi vesicles which are pinched off the end cisternae.
63
What is the cell wall made of in plants, algae and fungi?
* Plants and algae ->Cellulose
| * Fungi -> Chitin
64
What is the function of the cell wall?
* Provide strength -> Prevent damage due to osmotic movement
* Mechanical strength
* Allows water to pass along it
65
What structures are found in-between cell walls?
Middle lamella -> This is a thin layer found at the boundary between two cells, which cements cell walls together.
66
What is more outer, the cell membrane or the cell wall?
The cell wall
67
What does a vacuole contain?
Cell sap - a weak solution of sugars and salts.
68
What are the functions of a vacuole?
* Supports plants by making cells turgid
* Sugars and amino acids may serve as temporary food store
* Isolation of unwanted chemicals inside the cell
* Pigment may be colourful, which attracts insects
69
Describe the successive grouping of specialised cells.
Cells -> Tissues -> Organs -> Organ systems
70
What is a tissue?
A group of specialised cells working towards a particular function.
71
What are the different organelles found in prokaryotic (bacteria) cells? (8)
* Cell wall
* Cell-surface membrane
* Capsule
* Plasmid
* Ribosome
* Cytoplasm
* Genetic material
* Flagellum
72
What is different about organelles in the cytoplasm of prokaryotic cells compared to eukaryotic cells?
They are not membrane-bound, like in eukaryotic cells.
73
Which organelles in prokaryotic cells are only found in certain species?
* Flagellum
* Capsule
* Plasmid
74
What is the difference between ribosomes in eukaryotic and prokaryotic cells?
* Eukaryotic -> 80s ribosomes -> Larger
| * Prokaryotic -> 70s ribosomes -> Smaller
75
What is the cell wall made of in prokaryotic (bacteria) cells?
Murein - A glycoprotein
76
What is the capsule made from?
Secreted slime
77
What is the function of the capsule?
• Protects the bacteria from attacks by cells of the immune system
78
How many plasmids are in a bacterial cell?
There may be none, one or several.
79
What is a plasmid?
A small loop of DNA that isn't part of the main circular DNA molecule in a bacterial cell.
80
What is the function of a plasmid?
• It contains genes for things such as antibiotic resistance and can be passed between bacterial cells.
81
What organelles are prokaryotic cells lacking compared to eukaryotic cells?
* Nucleus
* RER and SER
* Golgi apparatus
82
What is the function of the flagellum?
• Rotates to make the cell move
83
Describe the genetic material in a prokaryotic cell.
* Circular DNA, as a long coiled-up strand.
| * Not attached to any histone proteins.
84
Are viruses cells?
No - they are acellular. They are simply nucleic acids surrounded by protein. They're not even alive.
85
What is the relative size of viruses?
They are very small - much smaller than bacteria.
86
How do virus organelles different from bacteria?
Viruses have no plasma membrane, cytoplasm or ribosomes.
87
Remember to revise the structure of a virus.
Pg 28 of revision guide.
88
What are the parts of a virus?
* Genetic material -> RNA or DNA
* Capsid
* Attachment proteins
89
What is the capsid in viruses?
A protein coat which surrounds the genetic material core.
90
What is the function of attachment proteins on viruses?
• Allow the virus to identify and attach to cells
91
What is the process by which prokaryotic cells divide called?
Binary fission
92
Describe binary fission.
1) Circular DNA and plasmids replicate. DNA loop replicates only once, but but plasmids can be replicated several times.
2) Cell gets bigger and DNA loops move to opposite poles of the cell
3) Cytoplasm divides.
4) Two daughter cells are produced.
93
Describe how viruses replicate.
1) Use attachment proteins to bind to complementary receptor proteins on surface of host cell
2) Most viruses can only infect one type of cell due to the fact that the proteins and receptors must be complementary
3) Viruses inject their DNA or RNA into the host cell, which forces it to replicate the virus
94
What is the formula for magnification?
Magnification = Size of Image / Size of Object
95
What is resolution?
How well a microscope distinguishes between two points that are close together.
96
What are the main types of microscope?
* Light microscopes
| * Electron microscopes -> Transmission and Scanning
97
What are the types of electron microscope?
* Transmission electron microscope (TEM)
| * Scanning electron microscope (SEM)
98
How does a light microscope work?
Light is passed upwards through the specimen. Thinner, less dense parts absorb less light and appear brighter. Most LM are compound, so they use two lenses to magnify the image.
99
Compare the resolution of light microscopes, TEMs and SEMs.
Light: 200nm
TEM: 0.1 nm
SEM: 20nm
100
Which organelles would you not be able to make out using a light microscope?
* Ribosomes
* Endoplasmic reticulum
* Lysosomes
101
Compare the magnification of light microscopes, TEMs and SEMs.
Light: x1,500
TEM: x1,500,000
SEM: x1,500,000
102
How does a transmission electron microscope work?
* Electron gun fires a beam of electrons from below, which is focused using an electromagnet
* More electrons pass through thinner, less dense parts of the specimen, making them appear brighter
* An image forms on a screen
103
How does a scanning electron microscope work?
* Beam of electrons from above is passed forwards and backwards over the specimen in a regular pattern.
* The contours on the specimen scatter electrons and the pattern in which this happens can be used by a computer to generate a 3D image
104
What are the advantages and disadvantages of electron microscopes over light microscopes?
```
ADV
• Better resolution
• Beam can be focused by electromagnets
• SEMs can produce 3D images
DIS
• Expensive
• Large
• Vacuum must be maintained
• Only thin specimen can be observed by TEM
• Specimen must be stained -> Image is not in colour
• Artefacts -> Preparation of specimen may alter finished photomicrograph
• Training is required
```
105
What are the advantages of TEMs and SEMs?
TEMs
• Give higher resolution images than SEMs
SEMs
• Can be used on thicker specimen than TEMs
106
What are plasmodesmata?
"Channels" in the cell wall for exchanging substances between adjacent cells.
107
How can a specimen be prepared for viewing under an optical microscope?
* Pipette a small drop of water onto the slide
* Place a thin section of your specimen on top using tweezers
* Add a drop of a stain
* Add the cover slip, standing it upright and then carefully lowering it down
108
What are the 3 main steps of cell fractionation?
* Homogenisation - breaking up cells
* Filtration - getting rid of the big bits
* Ultracentrifugation - separating the organelles
109
What is homogenisation?
Breaking up cells to release the organelles into a solution.
110
Give some ways in which homogenisation can be done.
* Vibrating the cells
| * Grinding the cells up in a blender
111
What are the conditions for homogenisation?
* Ice-cold
* Isotonic solution
* Buffer solution
112
During homogenisation, why must the solution be kept ice-cold?
To reduce the activity of enzymes that break down the cell organelles.
113
During homogenisation, why must the solution be isotonic?
To prevent movement of water and thus the damage of organelles by osmosis.
114
During homogenisation, why must a buffer solution be used?
To maintain the pH.
115
What is a buffer solution?
A solution which keeps the pH almost constant.
116
Why must the homogenised cell solution be filtered during cell fractionation?
To separate any large cell debris or tissue debris, like connective tissue, from the solution.
117
What is the process by which different organelles in a solution are separated called?
Ultracentrifugation
118
Describe the process of ultracentrifugation.
1) Cell fragments are poured into a tube, which is put into a centrifuge. The centrifuge spins at a low speed. The most dense organelles (e.g. nuclei) are flung to the end of the test tube. They form a thick sediment called a pellet. The rest remains as a fluid above, called the supernatant.
2) Supernatant is drained off and poured into another tube. This time it is spun at a higher speed. Once again, the most dense organelles form a pellet and the supernatant is separated out.
3) The process is repeated several times, with the pellet being made out of gradually lighter organelles each time.
119
What are the two types of cell division in eukaryotes?
Mitosis and meiosis
120
What is mitosis?
When a parent cell divides to produce two genetically identical daughter cells.
121
What is mitosis needed for?
* Growth
| * Repairing damaged tissues
122
What is the process of cells dividing by mitosis called?
The cell cycle.
123
What are the two MAIN parts of the cell cycle?
* Interphase
| * Mitosis
124
What is interphase?
The period of cell growth and DNA replication, when mitosis isn’t happening.
125
What are the three parts of interphase?
* Gap phase 1
* Synthesis
* Gap phase 2
126
What happens in gap phase 1 of interphase?
Cell grows and new organelles and proteins are made.
127
What happens in the synthesis phase of interphase?
Cell replicates its DNA, ready to divide by mitosis.
128
What happens in gap phase 2 of interphase?
Cell keeps growing and proteins needed for cell division are made.
129
Describe the order of the cell cycle stages.
* Mitosis
* Gap phase 1
* Synthesis
* Gap phase 2
130
What abbreviations are used in the cell cycle?
* Mitosis = M
* Gap phase 1 = G1
* Synthesis = S
* Gap phase 2 = G2
131
What is the order of the stages of mitosis?
```
(• Interphase)
• Prophase
• Metaphase
• Anaphase
• Telophase
```
132
What abbreviation can be used to remember the stages of mitosis?
PMAT
133
What happens in interphase?
* Cell carries out normal function
* DNA is unravelled and duplicated
* Organelles are also replicated
* ATP content is increased
(See diagram pg 32)
134
Describe the chromosomes at the start of mitosis and how they end up after mitosis.
* Two separate strands called chromatids
* Joined in the middle by a centromere
* This is because each chromosome has made a copy of itself already during interphase
* After mitosis, chromatids end up as one-strand chromosomes
135
Describe prophase.
* Chromosomes condense, getting shorter and fatter
* Centrioles start moving to opposite ends of the cells, forming a spindle
* Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
136
What is a centromere?
The part that joins the two chromatids in a chromosome (when the DNA has been duplicated).
137
What is a chromatid?
A single strand of DNA in a chromosome (when the DNA has been duplicated).
138
What are centrioles?
Tiny bundles of protein that hold the ends of the spindle in mitosis.
139
What is the spindle?
A network of fibres across the cell in mitosis which help pull the chromosomes to opposite sides.
140
Describe metaphase.
* Chromosomes line up along the middle of the cell
| * Centromeres attach to the spindle
141
Describe anaphase.
* Centromeres divide, separating each pair of sister chromatids
* Spindles contract, pulling chromatids to opposite poles of the spindle by the centromeres -> Chromatids appear v-shaped
142
Describe telophase.
* Chromatids reach opposite poles, uncoil, and become long and thin -> Now called chromosomes again
* Nuclear envelope forms around each group of chromosomes
* Cytoplasm divides and two daughter cells are formed
143
What is the cytoplasm dividing called?
Cytokinesis
144
In which stage of mitosis do the chromatids appear v-shaped?
Anaphase
145
Revise mitosis diagrams.
See pg 32 of revision guide.
146
Describe how a cancer can form.
* Mitosis and the cell cycle are controlled by genes
* Usually, after dividing enough times, the cell stops
* A mutation in the genes can cause cell growth to get out of control
* A tumour forms
147
Describe how some cancer treatments work and the drawback of this.
* The treatment disrupts the cell cycle -> This kills the cell
* However, this also affects healthy tissue
148
What are two examples of cell cycle targets for cancer treatments?
* Gap phase 1
| * Synthesis
149
Describe how cancer drugs target G1.
Mostly chemotherapy drugs:
• Prevent the synthesis of enzymes needed for DNA replication
• Without these, the cell can’t enter synthesis and is forced to kill itself
150
Describe how cancer drugs target the synthesis stage.
Mostly radiation and some drugs:
• Damage DNA
• The cell checks its DNA for damage before and during the S phase
• If severe damage is detected, the cell will kill itself.
151
Describe how a root tip can be prepared for observation under a microscope.
1) Cut 1cm from the tip of a growing root
2) Prepare a boiling tube containing 1M HCl and put it in a water bath at 60*C
3) Put the root tip into the water and incubate for 5 minutes
4) Use a pipette to rinse the root tip well with cold water. Leave to dry on a paper towel.
5) Place the tip on a microscope slide and cut 2mm from the end. Remove the rest.
6) Use a mounted needle to break the tip open and spread the cells out thinly.
7) Add a few drops of stain and leave for a few minutes.
8) Place a cover slip over the cells and press down to squash the tissue.
9) Observe under a microscope.
152
How can cells on a slide be observed using an optical microscope?
1) Clip the slide onto the stage
2) Select the low-powered objective lens
3) Use the coarse adjustment knob to bring the stage up to just below the lens.
4) Looking down the eyepiece, use the coarse adjustment knob to move the stage downwards until it is roughly in focus
5) Adjust the focus with the fine adjustment knob
6) Repeat with higher magnification if necessary
153
What is true formula for mitosis index?
Mitotic index = No. of cells in mitosis / Total no. of cells
154
What does the mitotic index tell us?
* How quickly the tissue is growing
| * High mitotic index might suggest cancerous growth or that tissue repair is happening
155
What is an eyepiece graticule?
A transparent ruler without units that is fitted onto the
156
What is a stage micrometers and what is it used for?
* A microscope slide with a an accurate scale (with units).
| * Used to work out the value of the divisions on the eyepiece graticule at a particular magnification.
157
Describe how a stage micrometer and eyepiece graticule work together.
A stage micrometer is used to calculate what length each division on the eyepiece graticule represents.
158
What formula relates the actual size of a cell, the size of the image and the magnification?
Actual size = Size of Image / Magnification
159
What are artefacts?
Things that you can see down the microscope that aren’t part of the cell or specimen.
160
Give some examples of artefacts.
* Dust
* Air bubbles
* Fingerprints
161
When are artefacts especially common and why?
• In electron micrographs • Because the specimen requires a lot of preparation before viewing under an electron microscope
