Section 2 - Cell Structure Flashcards
(193 cards)
1
Q
Define - Magnification
A
How much an image is enlarged under a microscope.
2
Q
What is magnification controlled by?
A
The power of the lens used.
3
Q
Define - Resolution
A
The minimum distance apart that two objects can be in order for them to appear as separate items
4
Q
What is resolution controlled by?
A
The wavelength of the illumination used
5
Q
Give ordered list of microscopes and their resolution power?
A
Light - low
SEM - high
TEM - Highest
6
Q
What does SEM stand for?
A
Scanning electron microscope
7
Q
What does TEM stand for?
A
Transmission electron microscope
8
Q
What are the advantages of using a TEM?
A
Transmission electron microscope
- highest magnification and resolution ( as shorter wavelength of electrons)
- focuses using a condenser electromagnet
- produces 2D photomicrograph (digital)
9
Q
What are the disadvantages of using a TEM?
A
Transmission electron microscope
- dead cells
- must be in a vaccum
- must cut specimen (thin specimen)
- complicated preparation may create artefact
- does not produce colour image
10
Q
Define - Artefact
A
Error caused with something that is not part of natural specimen
11
Q
How do TEM’s work?
A
Transmit electrons through a specimen
12
Q
How do SEM’s work?
A
They scan for electrons by detecting electrons that bounce off a specimen.
13
Q
What are the positives of using SEM’s?
A
Scanning electron microscope
- high resolution
- specimen doesn’t need to be thin
- focuses using a condenser electromagnet
- produces a 3D image using computer analysis
14
Q
What are the negatives of using a SEM?
A
- dead cells
- must be in a vacuum
- complicated preparation may create artefact
- does not produce colour images
15
Q
How can you calculate magnification?
A
Magnification = Image size / actual size
16
Q
How does an eyepiece graticule do?
A
It helps us measure the size of an object
It is a way to measure with a scale of 10mm and divided into 100 sub-divisions
17
Q
Why must you calibrate an eyepiece graticule?
A
All objective lenses have different degrees of magnification
18
Q
How do you calibrate an eyepiece graticule?
A
- use a microscope slide called a stage micrometre
- this provides a second scale
- line up the eyepiece graticule scale and the stage micrometre to calculate the length of the divisions on the eyepiece graticule
- To calculate divide the differences in magnification.
- You must give in graticule units (gu) eg. X10 Magnification 1mm = 10gu 1/10mm = 1gu 0.1mm = 1gu
19
Q
What is cell fractionation?
A
the process of breaking up cells and different organelles they contain in order to separate the organelles (by size) ready for study
20
Q
What is the process of cell fractionation?
A
stage 1 - cold, buffered and isotonic solution
stage 2 - homogenisation
stage 3 - sieve to remove insoluble material
stage 4 - ultracentrifugation
21
Q
what is stage 1 of cell fractionation?
A
Place fractionation cells in a cold, buffered and isotonic solution.
22
Q
what is stage 2 of cell fractionation?
A
Homogenisation - cells are broken up by a homogeniser to release the organelles
23
Q
Why are fractionation cells placed in a cold solution?
A
to reduce enzyme activity that could damage the organelles
24
Q
Why are fractionation cells placed in a buffered solution?
A
to maintain a constant pH and prevent protein damage
25
Why are fractionation cells placed in a isotonic solution?
to prevent cell organelles bursting or shrinking(osmosis out)
26
Define - homogenisation
cells are broken up by a homogeniser to release the organelles
27
What is a homogeniser?
Basically a blender that breaks up cells for fractionation
28
what is stage 3 of cell fractionation?
the blended tissue is **filtered** though a sieve to remove insoluble materials eg. cell wall, large pieces of unhomogenised tissue and connective tissue
29
what is stage 4 of cell fractionation?
Ultracentrifugation -
1. The **filtrate** is placed in **centrifuge** and **spun at a slow speed.**
2. The **heaviest organelles** eg. the nucleus are forces to the bottom and form a thin **pellet**.
3. The fluid at the top (**supernatant** ) is **removed**. The supernatant can be **re spun** at a faster rate to gain the next heaviest organelles.
4. You should **repeat** this until all organelles are separated.
30
How is the supernatant?
The fluid that stays at the top during ultracentrifugation
31
Which individual helped discover the cell?
Robert Hooke - 1665
32
Why was the electron microscope such an important discovery?
It allowed scientists to see the complete ultrastructure of the cell.
33
What does the nucleus consist of?
- nuclear envelope
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus
34
What is the nuclear envelope?
- **surrounds the nucleus**
- **lipid bilayer membranes**
- Outer membrane is continuous with the ER and often has ribosomes on its surface
- controlling the entry and exit of materials in and out of the nucleus and the reactions taking place within it
35
What are nuclear pores?
* Allow the transport of molecules across the nuclear envelope
* RNA moving from the nucleus and proteins moving to the nucleus
* It is like holes in the envelope.
* typically 3000 pores in each nucleus
* each 40-100 nm in diameter
36
What is the nucleoplasm?
A granular, jelly-like material. The substance in cell's nucleus that makes up the bulk of the nucleus and includes chromosomes and nucleolus
37
What are chromosomes?
- Made of nucleic acids and proteins - carries genetic information in the form of genes - consisting of protein-bound, linear DNA
38
What is nucleolus?
- A small spherical region within the nucleoplasm - It is the largest structure in the nucleus - It manufactures ribosomal RNA and assembles the ribosomes. - There may be more than one in a nucleus
39
What is the function of cytoplasm?
This is where all the reactions occur and it also holds all the organelles.
40
What is the function of the cell membrane?
This is selective and choses what goes in and out of the cell
41
What is the function of the ribosomes?
To secrete proteins. It is also made into a large and small section
42
What is the function of the mitochondria?
The power house of the cell - so aerobic respiration can produce energy in the form of glucose
43
What is the function of the cell wall?
To keep the structure off the plant cells. It is made of cellulose.
44
What is the function of the vacuole ?
This contains the cell sap and gives some structure
45
What does Mitochondria consist of?
- double membrane - cristae - matrix
46
What is the function of the double membrane?
- outer membrane covers mitochondria like a skin - inner membrane folds into a layered structure - the inner membrane increases the surface area
47
What is the function of the cristae?
- This is the fold made by the inner membrane of the mitochondria. - It gives more space for the attachment of enzymes and other proteins involved in respiration
48
What is the function of the matrix?
- The fluid inside the mitochondria - It has its own ribosomes and DNA floating in it - containing granules which help with ion concentration - Contains protein, lipids, ribosomes and DNA that allows the mitochondria to control the production of some of their own proteins - Many enzymes involved in respiration are found in the matrix
49
What is the function of their chloroplast?
It is the sight of photosynthesis
50
What does the chloroplast contain?
- Chloroplast envelope - grana - stroma
51
What is the function of the chloroplast envelope?
It is a double plasma membrane that surrounds the chloroplast organelles. It is highly selective in what it allows to enter and leave the chloroplast.
52
What is the function of the Grana?
- stacks of discs known as thylakoids up to 100 discs - within the thylakoids is the photosynthetic pigment chlorophyll - resembles a stack of coins - site of light-dependant reactions photosynthesis - connected by intergranal thylakoids - some have tubual extensions that join up with thylakoids in adjacent grana (where the first stage of photosynthesis takes place)
53
What is the function of stroma?
- colourless fluid surrounding grana - contains enzymes required for photosynthesis - DNA and ribosomes are also present - a fluid filled matrix where the second stage of photosynthesis takes place (synthesis of sugars) - also includes starch grains
54
What are the two types of endoplasmic reticulum ?
rough and smooth
55
What are the functional differences between the types of endoplasmic reticulum ?
rough - has ribosomes attached - involved in protein synthesis smooth - to do with lipids - other molecules are synthesised
56
What is the resolving power of a light microscope?
0.2pm - means that any objects closer than that will appear as a single item.
57
What is a limit of resolution?
It is up to this point that increasing magnification will reveal more detail but beyond it increasing the magnification will not do this and the item while larger will be more blurred
58
Why do light microscopes have a poor revolution?
A result of a relatively long wavelength of light
59
What is the advantage of electron microscopes over light microscopes?
- the electron beam has a very short wavelength and the microscope can therefore resolve objects well - it has a high resolving power - as electrons are negatively charged the beam can be focused using electromagnets
60
What is the revolution power of electron microscopes?
0.1nm apart - 2000 times better than a light microscope
61
What must be created in the chamber of an electron microscope in order for it to work effectively?
A near-vacuum
62
What is a graticule?
A glass disc that is placed in the eyepiece of a microscope. There is a scale etched on the glass disc.
63
Why would you record the results of calibration?
- If a specific objective lens then you can leave this attached to the microscope saving you time to have to recalibrate each time you use to measure the size of the object being viewed under the microscope
64
What is an ultrastructure?
The internal structure that suits the cells specific function.
65
What do eukaryotic cells have?
A distinct nucleus and possess membrane-bounded organelles
66
What is the function of the nucleus?
- Act as the control centre of the cell through the production of mRNA and tRNA and hense protein synthesis - retain the genetic material of the cell in the form of DNA and chromosomes - manufacture ribosomal RNA and ribosomes
67
What does the nucleus contain?
the organism's hereditary material and controls the cells activity. Its using spherical
68
What is the role of mitochondria?
sites of aerobic stages of respiration (Krebs cycle and the oxidative phosphorylation pathway) - therefore responsible for the production of energy-carrier molecule, ATP, from respiratory substances such as glucose. - The number of mitochondria will vary with the level of metabolic activity
69
How are chloroplasts adapted for their function?
- granal membrane provides a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis. These chemicals are attached to the membrane in a highly ordered fashion - the fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis - chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
70
What is the ER?
Endoplasmic Reticulum
It is continuous with the outer nuclear membrane,
network of tubules and flattened sacs called cisternae
71
What is the function of the rough ER?
1. Provide a large surface area for the synthesis of proteins and glycoproteins 2. Provide a pathway for the transport of materials, especially proteins, throughout the cell
72
What is the function of the smooth ER?
- synthesise, store and transport lipids - synthesise, store and transport carbohydrates
73
Describe the structure of the golgi apparatus?
- Similar to the SER but is more compact - stacks of membranes that make up flattened sacs (cisternae) with small rounded hollow structures called vesticles - Proteins made in ER pass though in strict sequence - The golgi modifies these proteins often adding non-protein components eg. carbohydrates. - Also labelling them allowing them to be accurately sorted adn sent to correct destinations - once sorted the proteins and carbohydrates are transported in Golgi cisternae - These vesicles may move to the cell surface, where they fuse with the membrane and release their contents to the outside
74
What is the function of the Golgi Apparatus?
- Add carbohydrate to proteins to form glycoproteins - produce secretory enzymes, such as those secreted by the pancreas - secrete carbohydrates, such as those used in making cell walls in plants - transport, modify and store lipids - form lysosomes
75
In what cells are Golgi Apparatus' especially well developed?
Well developed in secretory cells, such as the epithelial cells that line the intestines
76
How are lysosomes formed?
When the vesicles produced by the Golgi Apparatus contain enzymes such as proteases and lipases.
77
What are lysozymes?
Enzymes that hydrolyse the cell walls of certain bacteria.
78
How many enzymes may be contained in a single lysosomes
as many as 50
79
What size are lysosomes?
up to 1.0 pm in diameter
80
What is the function of lysosomes?
- hydrolyse material ingested by phagocytic cells, such as white blood cells and bacteria - release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell - digest worn out organelles so that the useful chemicals they are made of can be re-used - completely break down cells after they have died (autolysis)
81
What cells have abundant lysosomes?
secretory cells - epithelial cells and phagocytic cells
82
What are ribosomes?
small cytoplasmic granules found in all cells. They may be in the cytoplasm or the RER
83
What are the two types of ribosomes and where are they found?
- 80S - in eukaryotic cells around 25nm in diameter - 70S - in prokaryotic cells, mitochondria and chloroplasts and is slightly smaller
84
What is the function of ribosomes?
- site of protein synthesis - made of two subunits (one large and one small) - each containing ribosomal RNA and protein - despite their small size they occur in such high vast numbers that they account for 25% of the dry mass of the cell
85
How much of the cells dry mass is made up of ribosomes?
25%
86
What is the cell wall made up of?
In all plant cells, it consists of microfibrils of the polysaccharide, cellulose, embedded in a matrix.
87
What is the function of cellulose microfibrils?
They have considerable strnegth and so contribute to the overall strength of the cell wall.
88
What features do cell walls have?
- consist of a number of polysaccharides such as cellulose - a thin layer called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together
89
What is the middle lamella?
A thin layer which marks the boundary between adjacent cell walls and cements adjacent cells together
90
What is the functions of the cellulose cell wall?
- provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water - to give mechanical strength to the plant as a whole - to allow water to pass along it and so contribute to the movement of water through the plant
91
What are the cell walls of algae made off?
Either cellulose or glycoproteins or a mixture of both
92
What are the cell walls of fungi made off?
comprise a mixture of a nitrogen-containing polysaccharide called chitin, a polysaccharide called glycan and glycoproteins
93
What is chitin?
A nitrogen-containing polysaccharide
94
What are vacuoles made of?
A fluid-filled sac bounded by a single membrane.
95
What is the tonoplast?
The single membrane around a mature plant cells vacuole.
96
What solution is in a plants vacuole?
Mineral salts, sugars, amino acids, wastes and sometimes pigments such as anthocyanin
97
What is anthocyanin?
A pigment in plant vacuoles
98
What are the functions of plant vacuoles?
- support herbaceous plants, and herbaceous parts of woody plants, by making cells turgid - the sugars and amino acids may act as a temporary food store - the pigments may colour petals to attract pollinating insects
99
What are the two main types of cells?
- Eukaryotic cells - Prokaryotic cells
100
Whats the difference between the different types of cells?
Eukaryotic cells - Larger and have a nucleus bounded by nuclear membranes (nuclear envelope) Prokaryotic cells - Smaller and have no nucleus or nuclear envelope.
101
what are three characteristics of bacterial cells?
- versatile - adaptable - Very successful
102
What is the normal size of a bacterial cell?
0.1-10 pm in length
103
What is the cell wall in bacterial cells made off?
murein - this is a polymer of polysaccharides and peptides.
104
How do bacterial cells further protect themselves?
They have a Capsule of mucilaginous slime around the cell membrane and wall
105
What type of ribosome is in bacterial cells?
70S - which are smaller than those in the cytoplasm of eukaryote cells (80S) but still synthesis proteins
106
What food does bacteria store?
- Glycogen - Granules - Oil droplets
107
What is the genetic material in bacterial cells?
- Circular strand of DNA - Plasmids These can reproduce themselves independently and may give the bacterium resistance to harmful chemicals, such as antibiotics
108
What are plasmids used as?
As vectors in genetic engineering.
109
What is a vector?
A carrier of genetic information
110
List the cell structure in bacterial cells.
- Cell wall - Capsule - Cell-surface membrane - Circular DNA - Plasmid - Flagellum
111
What is the role of the cell wall in bacterial cells?
It is a physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis
112
What is the role of the capsule in bacterial cells?
This protects bacterium from other cells and helps groups of bacteria to stick together for further protection.
113
What is the role of the cell-surface membrane in bacterial cells?
This acts as differentially permeable layer, which controls the entry and exit of chemicals
114
What is the role of the circular DNA in bacterial cells?
This possesses the genetic information for the replication of bacterial cells
115
What is the role of the plasmid in bacterial cells?
This possesses genes that may aid the survival of bacteria in adverse conditions eg. Produces enzymes that break down antibiotics
116
What is the role of the flagellum in bacterial cells?
There may be more than one but only in certain species - Used for locomotion
117
What is the role of the cytoplasm in bacterial cells?
It is a jelly-like substance that contains enzymes and other soluble materials. Where reactions take place
118
What is the role of the ribosomes in bacterial cells?
They are smaller than in eukaryote (80S-70S) They synthesis proteins
119
How thick are the cell walls in bacterial cells?
10-80 nm
120
What are viruses?
They are acellular, non-living particles
121
What genetic information do viruses contain?
Nucleic acids such as DNA and RNA
122
What is the ranging in size of a virus?
20-300nm
123
What encloses the nucleic acids in virus'?
Within a protein coat calles a capsid
124
What cells are surrounded by a lipid envelope?
human immunodeficiency virus
125
What is attached to the outer layer of virus cells?
Attachment proteins
126
What is the role of attachment proteins?
They are essential to allow the virus to identify and attach to a host cell.
127
List the structure of a virus cell.
- Attachment proteins - Lipid envelope - Matrix - capsid - nucleoproteins - Genetic material (RNA and DNA)
128
Explain how virus' replicate
1. Virus attaches to host cell using there attachment proteins and injects it with nucleic acid 2. genetic material used as code to synthesise proteins providing instructions for the host cells metabolic processes to start producing the viral components, nucleic acid, enzymes and structural proteins. 3. New virus particles are assembled 4. Viruses burst out of, and destroy, host cells
129
What is the function of attachment proteins in virus cells?
They make it possible to attach the virus to host cells
130
What is the function of the lipid envelope in virus cells?
This is derived from the host cell's membrane making it easy to attach
131
What is the function of genetic information in virus cells?
RNA and DNA encode virus proteins
132
What is the function of nucleoproteins in virus cells?
eg. Enzymes These are accessory proteins
133
What is the function of the capsid in virus cells?
This is a protein coat that encapsulates the DNA/RNA
134
What is the function of the matrix in virus cells?
This is the protein layer on the inside of the envelope.
135
What is the difference between mitosis and meiosis?
-Mitosis - produces two daughter cells that have the same number of chromosomes as the parent cell and each other - Meiosis - produces four daughter cells, each with half the number of chromosomes of the parent cell.
136
Define - Mitosis
The division of a cell that results in each of the daughter cells having an exact copy of DNA of the parent cell.
137
If there is a mutation how would this effect mitosis?
The genetic makeup of the two daughter nuclei is also identical to that of the parent nucleus.
138
What happens during interphase?
Considerable cellular activity that includes a very important event, the replication of DNA. The two copies of DNA remain joined at the place called the centromere.
139
Name the stages of Mitosis
- Prophase - Metaphase - Anaphase - Telophase - Cytokinesis
140
Explain what happens during prophase.
- The chromosomes become visible, (initially long and thin threads then shorter and thicker) - The two cylindrical organelles called centrioles move to opposite sides of the cells - Spindle fibres develop from each centriole. - The nucleolus disappears and the nuclear envelope breaks down leaving chromosomes free in the cytoplasm - These chromosomes are drawn towards the equator by the spindle fibres attached to the centromere
141
What is a collection of spindle fibres called?
spindle apparatus
142
Explain the metaphase
* - The chromosomes two chromatids.
* parents joined by centremere
* centremere pull along spindle apparatus
* **arrange on equator**
143
Explain the anaphase
- Centromeres divide into two and **spindle fibres pull the individual chromatids to their respective, opposite poles.**
- The energy for the process is provided by mitochondria which is gathered around the spindle fibres.
144
What would happen if the cells are treated with chemicals?
This will destroy the spindle and the chromosomes will remain at the equator unable to reach the poles
145
Explain Telophase
- Chromosomes reach their respective poles and become longer and thinner - They finally disappear altogether leaving only widely spread chromatin. - The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form.
146
Describe cytokinesis
The process of the cytoplasm dividing
147
Explain the process of binary fission
- the circular DNA molecules replicates and both copies attach to the cell membrane - The plasmids also replicate - The cell membrane begins to grow between the two DNA molecules and pinch inwards, dividing the cytoplasm into two. - The new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmid
148
What are the three stages of the cell cycle?
1. Interphase - most of the cell cycle and AKA the resting phase and no division takes place 2. Nuclear division - WHen the nucleus divides euther into 2 or 4 3. Cytokinesis - The division of the cytoplasm to produce two or four new cells
149
What is the typical length of a cell cycle in mammals?
24 hours
150
How much of the cell cycle is interphase?
90%
151
How many cancers are there?
Around 200
152
What causes cancer?
It is a group of diseases caused by a growth disorder of cells which is the result of damage to the genes that regulate mitosis and the cell cycle leading to an uncontrolled growth and division of cells. As a result a tumour is formes and constantly expands in size.
153
Where are tumours most commonly found?
The lungs, Prostate gland (male), breast and ovaries (female), large intestine, stomach, oesophagus and pancreas
154
What are the types of tumours?
- Benign - Slow acting, stay in one place and aren't called cancerous - Malignant - fast acting, spreads though the bloodstream and is cancerous
155
How are tumours created?
A mutation to one of the two types of genes results in uncontrolled mitosis. the mutant cells so formed are usually structurally and functionally different form normal cells. Most mutated cells dies but those that don't are capable of dividing to form clones of themselves and from tumours.
156
What is a malignant tumour?
Is rapidly growing, less compact and are more likely to be life threatening. They are cancerous
157
What is a benign tumour?
Slowly growing, more compact and are less likely to be life threatening.
158
What does the treatment of cancer involve?
The killing of dividing cells by blocking a part of the cell cycle. It disrupts the cell cycle and cell division and hence cancer growth cease.
159
What are the ways to treat cancer?
- Surgery (benign) - Chemotherapy - Radiotherapy
160
How does chemotherapy treat cancer?
Drugs - prevents DNA from replicating - Inhibiting the metaphase stage of mitosis by interfering with spindle formation
161
What is the problem with chemotherapy ?
It can disrupt the cell cycle of normal cells
162
What are the positives of chemotherapy ?
They are more effective against rapidly dividing cells. Stoping a greater degree of damage to cells. Those body cells that are also rapidly dividing are also vulnerable to damage.
163
How can hair loose in cancer patients be explained?
A cancer cell has a particularly fast rate of division and so other body cells like hair-producing cells that also divide rapidly are also vulnerable to damage.
164
Explain cell specialisation
When cells of multicellular organisms are each specialised in a different way to carry out its only unique function.
165
How are cells in an organism produced?
mitotic divisions from the fertilised egg. So they all have the same genes
166
How does a cell become specialised?
Every cell contains the genes needed for it to develop into any one of the different cells in an organism. But only some of these genes are switched on (expressed) in any one cell, at any one time. Different genes are switched on in each type of specialised cell and the rest are switched off.
167
What is a tissue?
Collection of similar cells that perform a specific function.
168
What are epithelial tissue?
Found in animals and consist of sheets of cells. They line the surfaces of organs and often have a protective or secretory function. There are many similar types, including those made up of thin, flat cells that line organs where diffusion takes place eg. alveoli in the lungs and ciliated epithelium that lines a duct such as the trachea
169
What is the cilia?
These are used to move mucus over the epithelial surface eg. In the trachea
170
What are Xylem?
Occurring in plants and made up of a number of similar cell types. It is used to transport water and mineral ions throughout the plant and also gives mechanical support.
171
Give two example of tissues
- Xylem tissue - Epithelial tissue
172
What makes up an organ?
An organ is a combination of tissues that are coordinated to perform a variety of functions although they often have one predominant major function
173
What tissue is the stomach made up of?
- Muscle to churn and mix the stomach contents - Epithelium to protect the stomach wall and produce secretion - Connective tissue to hold together the other tissues
174
What tissues are leaves made off?
- **Palisade mesophyll** - photosynthesis
- **Spongy mesophyll** - gaseous diffusion
- **Epidermis** - protect the leaf and allow gaseous diffusion
- **Phloem** - transport the organic materials away from the leaf
- **xylem** - transport water and ions into the leaf
175
What is an organ system?
Organs that work together as a single unit. These systems may be grouped together to perform particular functions more efficiently.
176
What are examples of organ systems in humans?
- Digestive system - Respiratory system - Circulatory system
177
What is the digestive system made up of?
Organs such as the salivary glands, oesophagus, stomach, duodenum, ileum, pancreas and liver
178
What is the respiratory system made up off?
organs such as the trachea, bronchi and lungs
179
What is the circulatory system made up of?
Organs like the heart, arteries and veins.
180
Define - Chromatin
DNA when it is not wound up tightly as a chromosome
181
Define - Chromosome
A compact x or I shaped form of chromatin formed during cell division
182
Define - Chromotids
the two identical arms of the X-shaped chromosomes
183
Define - Centromere
Point at which chromosomes are joined
184
Define - Homologous Chromosomes
Two chromosomes originating from each parent. Containing the same genes, but different allele
185
What is the role of the nucleolus?
Make ribosomes
186
What are the stages of the cell cycle?
Interphase Cytokinesis Nuclear division
187
What is the role of lysosomes?
Breaks down waste materials
188
What type of ribosome is found in the eukaryotic cell?
80s
189
What is the role of the grana in the chloroplasts?
Photosynthesis
190
What phase of mitosis are spindle fibres formed?
prophase
191
What phase of mitosis does the nuclear envelope break down?
Metaphase
192
What phase of mitosis does the nuclear envelope reform?
Telophase
193
Required Practical 2
How can you prepare a slide of stained squashes of cells from plant root tips to identify the stages of mitosis?
1. Stand the beaker on a bench mat and add 10 ml of hydrochloric acid ). Label paper towel on bench mat
2. Place 2 cm of root tip in the acid - leave for 15 minutes.
3. Set up your microscope while you are waiting.
4. Rinse the root tip in distilled water in the watch glass.
5. Cut off the root tip (1mm) - place on microscope slide.
6. Cover with toluidine blue stain and macerate (needle to separate cells) - until tissue broken and stained blue
7. Use a piece of white paper to aid colouration of roots.
8. Add a cover slip - gentle finger pressure to ‘spread’ - blot using a folded filter paper between finger and slide.
9. Look carefully at all slides for cells undergoing mitosis. Chromosomes should stain dark blue. Repeat for several fields of view.
10. Record your data in a suitable table.
11. Calculate the mitotic index
