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52 Cards in this Set
- Front
- Back
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How far apart do objects have to be for a light microscope to distinguish them as separate objects? |
0.2 micrometers (um) |
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How close together do two objects need to be for the electron microscope to distinguish them as separate objects? |
0.1 nanometers (nm) |
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What is the equivalent in metres of a micrometer? |
1x10^-6 |
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What is the equivalent in meters to a nanometer? |
1x10^-9 |
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Magnification = |
Size of image / size of real object |
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Why is magnification? |
How many times bigger the image is compared to the object |
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What is resolution? |
The minimum distance apart 2 objects have to be to be seen as separate objects |
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What is cell fractionation? |
It's the process where cells are broken up and the different organelles are separated out |
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What 3 things does a solution need to be in order for cell fractionation to begin? |
1. Cold - to reduce enzyme activity, which has the potential to break down the organelles 2. Buffered - so that the pH does not fluctuate, as this could change structure of organelles or change functioning of enzymes 3. Isotonic - to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water. |
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What are the 2 stages of cell fractionation? |
1. Homogenation - cells are broken up by homogeniser. This releases the organelles from the cell. The resultant fluid is called a homogenate and is filtered to remove any complete cells or debris. 2. Ultracentrifugation - process by which the fragments in the homogenate are separated in a machine called a centrifuge, where solution is spun at very high speed in order to create a centrifugal force. |
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Describe the process of ultracentrifugation for animal cells: |
1. Tube is spun at low speed in centrifuge 2. Heaviest organelles are forced to bottom of tube, forming thin sediment 3. Fluid at top, SUPERNATENT, is removed 4. The supernatent is put in new tube and spun at faster speed 5. Next heaviest organelles are forced to bottom 6. Process is repeated |
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Light microscopes are not as good as electron microscopes because.... |
Light has a long wavelength and so has a poor resolution |
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What are the two main advantages of the electron microscope? |
1. Electron beam has short wavelength and so microscope can resolve objects well 2. As electrons are negatively charged the beam can be focused using electromagnets |
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Why does a near-vacuum need to be created in the chamber of a electron microscope? |
As electrons are absorbed or deflected by molecules in the air, affecting the microscopes accuracy |
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How does the TEM work? |
Consists of electron gun which focuses a beam of electrons into the specimen by a condenser electromagnet. Parts of the specimen will absorb the electrons, appearing dark in image. Parts of the specimen allow the electrons to pass through, this is shown by a light colour. |
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What are the main limitations of the TEM ? |
1. Vacuum is needed, therefore no living specimens can be observed. 2. Staining of specimen is required, which is a complicated process 3. Specimen needs to be extremely thin 4. Image may contain artefacts, which are small alterations as a result of preparing the specimen. This affects the true image of the specimen |
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What image is produced by a TEM? |
Flat, 2-D image |
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How does the SEM work? |
By scanning the electron beam back and forth over the surface of the specimen. The electrons are scattered by it and the pattern is analysed to build up a 3D image. |
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Compare SEM to TEM |
SEM has all same limitations as the TEM. However the specimen doesn't need to be so thin, as electrons are not penetrating it. The SEM has a lower resolving power though |
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What is difference between Euk and Pro cells? |
Euk have a distinct nucleus whereas Pro cells don't |
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What is difference between Euk and Pro cells? |
Euk have a distinct nucleus whereas Pro cells don't |
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List 9 parts of a Euk cell |
1. Nucleus 2. Mitochondria 3. Ribosomes 4. Chloroplasts 5. Lysosomes 6. Cell wall 7. Vacuole 8. Endoplasmic reticulum 9. Golgi apparatus |
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Describe nucleus |
Contains DNA and controls cells activity Double membrane (nuclear envelope - controls what enters and leaves. Nucleoplasm - jelly like material which makes up bulk of nucleus Nuclear pores - allow passage of large molecules Nucleolus manufactures ribosomal RNA and assembles the ribosomes |
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Describe nucleus |
Contains DNA and controls cells activity Double membrane (nuclear envelope - controls what enters and leaves. Nucleoplasm - jelly like material which makes up bulk of nucleus Nuclear pores - allow passage of large molecules Nucleolus manufactures ribosomal RNA and assembles the ribosomes |
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Describe mitochondria |
Rod shaped Double membrane Cistae - provide large SA for attachment of enzymes and other proteins involved in respiration Matrix - contains proteins, lipids, ribosomes and DNA Site of respiration |
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Describe nucleus |
Contains DNA and controls cells activity Double membrane (nuclear envelope - controls what enters and leaves. Nucleoplasm - jelly like material which makes up bulk of nucleus Nuclear pores - allow passage of large molecules Nucleolus manufactures ribosomal RNA and assembles the ribosomes |
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Describe mitochondria |
Rod shaped Double membrane Cistae - provide large SA for attachment of enzymes and other proteins involved in respiration Matrix - contains proteins, lipids, ribosomes and DNA Site of respiration |
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Describe chloroplasts |
Carry out photosynthesis. Double membrane which is highly selective. Large SA |
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Describe nucleus |
Contains DNA and controls cells activity Double membrane (nuclear envelope - controls what enters and leaves. Nucleoplasm - jelly like material which makes up bulk of nucleus Nuclear pores - allow passage of large molecules Nucleolus manufactures ribosomal RNA and assembles the ribosomes |
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Describe mitochondria |
Rod shaped Double membrane Cistae - provide large SA for attachment of enzymes and other proteins involved in respiration Matrix - contains proteins, lipids, ribosomes and DNA Site of respiration |
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Describe chloroplasts |
Carry out photosynthesis. Double membrane which is highly selective. Large SA |
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Describe RER |
Has ribosomes present. Provides large SA for synthesis of proteins and glycoproteins Provides pathway for transport of materials throughout cell |
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Describe nucleus |
Contains DNA and controls cells activity Double membrane (nuclear envelope - controls what enters and leaves. Nucleoplasm - jelly like material which makes up bulk of nucleus Nuclear pores - allow passage of large molecules Nucleolus manufactures ribosomal RNA and assembles the ribosomes |
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Describe mitochondria |
Rod shaped Double membrane Cistae - provide large SA for attachment of enzymes and other proteins involved in respiration Matrix - contains proteins, lipids, ribosomes and DNA Site of respiration |
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Describe chloroplasts |
Carry out photosynthesis. Double membrane which is highly selective. Large SA |
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Describe RER |
Has ribosomes present. Provides large SA for synthesis of proteins and glycoproteins Provides pathway for transport of materials throughout cell |
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Describe SER |
Lacks ribosomes. Synthesises, stores and transports lipids and carbohydrates |
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Describe Golgi apparatus |
Consists of stack of membranes that make up flattered sacks, or cisternae, with small hollow structures called vesicles. The proteins made by the ER are passed into the Golgi apparatus. Here they are modified and then released to perform their function. The Golgi apparatus forms lysosomes and produces secretory enzymes. |
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Describe Golgi apparatus |
Consists of stack of membranes that make up flattered sacks, or cisternae, with small hollow structures called vesicles. The proteins made by the ER are passed into the Golgi apparatus. Here they are modified and then released to perform their function. The Golgi apparatus forms lysosomes and produces secretory enzymes. |
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Describe Lysosomes |
They release enzymes which destroy material outside of the cell. Digest worn out organelles Have many secretory enzymes |
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Describe Golgi apparatus |
Consists of stack of membranes that make up flattered sacks, or cisternae, with small hollow structures called vesicles. The proteins made by the ER are passed into the Golgi apparatus. Here they are modified and then released to perform their function. The Golgi apparatus forms lysosomes and produces secretory enzymes. |
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Describe Lysosomes |
They release enzymes which destroy material outside of the cell. Digest worn out organelles Have many secretory enzymes |
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Describe ribosomes |
Occur in cytoplasm or RER |
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Describe Golgi apparatus |
Consists of stack of membranes that make up flattered sacks, or cisternae, with small hollow structures called vesicles. The proteins made by the ER are passed into the Golgi apparatus. Here they are modified and then released to perform their function. The Golgi apparatus forms lysosomes and produces secretory enzymes. |
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Describe Lysosomes |
They release enzymes which destroy material outside of the cell. Digest worn out organelles Have many secretory enzymes |
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Describe ribosomes |
Occur in cytoplasm or RER |
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5 parts of a Projaryotic bacteria cell? |
Cell wall Capsule Cell surface membrane Circular DNA Plasmid |
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5 parts of a Projaryotic bacteria cell? |
Cell wall Capsule Cell surface membrane Circular DNA Plasmid |
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Function of capsule? |
Protects bacterium from other cells and helps groups of bacteria to stick together |
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5 parts of a Projaryotic bacteria cell? |
Cell wall Capsule Cell surface membrane Circular DNA Plasmid |
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Function of capsule? |
Protects bacterium from other cells and helps groups of bacteria to stick together |
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Function of plasmid? |
Possesses genes that may aid survival of bacteria in adverse conditions |
