Cells - From Spec.

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  • Created by: rachel
  • Created on: 04-03-13 15:50
What's the resolution & magnification of the light microscope?
Resolution: 200nm. Magnification: x1,500.
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What's the resolution & magnification of the TEM?
Resolution: 0.1nm. Magnification: x500,000.
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What's the resolution & magnification of the SEM?
Resolution: 0.1nm Magnification: x100,000
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What are the images like that the SEM produces? What can be seen?
3-D picture & cell surface structures can be seen.
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What are the images like that the TEM produces? What can be seen?
2-D picture & details of organelles can be seen.
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What's the definition of resolution?
The degree to which it is possible to distinguish between two objects that are very close together. It allows the viewer to see detail.
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What's the definition of magnification?
The number of times larger the image is compared to the object.
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Why is there a need for staining samples for use in light microscopy?
A lot of biological material isn't coloured so it may be difficult to distinguish between different features. Coloured stains are used to stain specimens with the use of a light microscope. Chemicals bind to other chemicals in/on specimen - can be se
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Why is there a need for staining samples for use in electron microscopy?
Electron micrographs start off black & white, the colour is added by a specialised computer afterwards.
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Give an example of a chemical which binds to a specific structure to produce a red stain.
Actin orcein staining DNA red.
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How do you calculate the linear magnification of an image?
Magnification = Image size / Actual size. (use IAM triangle).
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On a photograph, how could you spot the Nucleus?
It's the largest organelle.
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On a photograph, how could you spot the Nucleolus?
It's a dense, spherical structure inside the nucleus.
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On a photograph, how could you spot the Nuclear envelope?
It surrounds the nucleus.
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On a photograph, how could you spot the RER & ER?
It is continuous with nuclear envelope. RER is studded with ribosomes. SER is not.
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On a photograph, how could you spot the Golgi apparatus?
It is a sack of membrane-bound flattened sacs.
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On a photograph, how could you spot Ribosomes?
They are tiny. Some are in the cytoplasm & some are bound to the RER.
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On a photograph, how could you spot the Mitochondria?
They are spherical or sausage shaped & have a double membrane.
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On a photograph, how could you spot the Lysosomes?
They are spherical sacs with a single membrane.
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On a photograph, how could you spot the Chloroplasts?
They are only in plant cells & have two membranes. They contain Thylakoids.
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On a photograph, how could you spot the Plasma (cell surface) membrane?
Phospholipid bilayer.
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On a photograph, how could you spot the Centrioles?
They are small tubes of protein fibres. There are a pair of them next the the nucleus in animal cells.
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On a photograph, how could you spot the flagella & cilia?
They have hair-like extensions projecting from the surface of a cell.
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What are the functions of the Nucleus?
It houses all the cells genetic material in the form of DNA, which contains the instructions for protein synthesis.
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What are the functions of the Nucleolus?
It makes ribosomes & RNA which passes into the cytoplasm & are used in protein synthesis.
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What are the functions of the Nuclear envelope?
It has a double membrane with nuclear pores to allow mRNA out to go to the ribosomes for use in protein synthesis.
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What are the functions of the RER?
It transports proteins made by the attached ribosomes.
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What are the functions of the ER?
It is involved in the making of lipids.
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What are the functions of the Golgi apparatus?
It modifies proteins received from RER & then packages them into vesicles so they can be transported. It also produces Lysosomes.
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What are the functions of the Ribosomes?
They are the site of protein synthesis.
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What are the functions of the Mitochondria?
It is where ATP is made.
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What are the functions of the Lysosomes?
They contain lysins which are digestive enzymes which break down organelles, pathogens & cells. When a cell dies it undergoes autolysis under the direction of lysosomes.
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What are the functions of the Chloroplasts?
They are the site of photosynthesis in plants.
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What are the functions of the Plasma (cell surface) membrane?
It controls entry & exit of substances into & out of the cell.
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What are the functions of the Centrioles?
They form the spindle that moves chromosomes during cell division.
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What are the functions of Flagella & Cilia?
They move by using ATP. e.g. they wave mucus along trachea or make sperm swim.
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whats the first step of the production & secretion of proteins?
1. The gene containing the instructions for the production of the hormone is copies onto a piece of mRNA.
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whats the second step of the production & secretion of proteins, after the gene has been copied into mRNA?
2. mRNA leaves the nucleus through the nuclear pore.
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whats the third step of the production & secretion of proteins, after the mRNA has left the nucleus?
3. mRNA attaches to a ribosome.
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whats the fourth step of the production & secretion of proteins, after the mRNA attaches to a ribosome?
4.The ribosome reads the instruction to assemble the protein.
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whats the fifth step of the production & secretion of proteins, after the ribosome has assembled the protein?
5. The molecules are pinched off in vesicles & travel towards the Golgi apparatus.
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whats the sixth step of the production & secretion of proteins, after the molecules are pinched off in vesicles & travel to Golgi apparatus?
6. The vesicle fuses with the Golgi apparatus.
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whats the seventh step of the production & secretion of proteins, after the vesicle fuses with the Golgi apparatus?
7. The Golgi apparatus processes & packages the molecules, ready for release.
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whats the eighth step of the production & secretion of proteins, after the molecules are processed & packaged & are ready for release?
8. The molecules are pinched off in vesicles from the Golgi apparatus & move towards the cell surface membrane.
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whats the ninth step of the production & secretion of proteins, after the molecules are pinched off in vesicles from Golgi apparatus & move towards cell surface membrane?
9. The vesicle fuses with the cell surface membrane.
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Finally, whats the tenth step of the production & secretion of proteins?
10. The cell surface membrane opens to release molecules outside. This is exocytosis.
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Explain the importance of the cytoskeleton in providing mechanical strength.
It provides strength stability & support to cells
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Explain the importance of the cytoskeleton aiding transport within cells.
Determines shape & changes shape by moving the membrane for endo & exocyt. Move organelles such as mitochondria, RNA, proteins & chromosomes. Moves vesicles along microtubule tracks using ATP. Holds organelles in place. Make up centrioles & spindle f
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Explain the importance of the cytoskeleton in enabling cell movement.
MIcrotubules don't move, they provide an anchor for the protein to move along. Using ATP it swivels pushing the organelle along. The head reattaches itself to microtubule & process is repeated.
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Explain how Flagella move.
Flagella move with the aid of the protein, Dynein. When a molecule of dyne in 'swivels' it pulls one microtubule past the next, causing cilium to bend.
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Describe the movement of cilia.
Cilia move out of time with each other to create a 'wave'.
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Describe a prokaryote.
Cells that do not have a nucleus. They are bacteria & are much smaller than Eukaryotic cells.
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Describe what prokaryotes 'have'.
One membrane, no membrane-bound organelles, a cell wall made of peptidoglycan (not cellulose), smaller ribosomes, circular DNA, DNA isn't surrounded by membrane, some have flagella, ATP production takes place in mesosomes.
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What are mesosomes?
Specialised in-folded regions of the cell surface membrane, where ATP production takes place.
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Describe a plant cell.
Contains a cell wall thats outside of the cell surface membrane & is made of cellulose, this forms sieve-like network of strands which make cell wall strong. Kept rigid by the pressure of fluid inside cell, so supports cell & plant. Contains vacuole.
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What does a vacuole do inside a plant?
A vacuole maintains cell stability by making the cell turgid as it increases the pressure inside the cell. This in turn helps support the plant.
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