BIOLOGY REVISION

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What's magnification?
The degree to which the size of an image is larger then the object itself
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What's resolution?
How far apart to objects need to be in order to be seen as seperate
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What's the resolution of light microscopes?
200nM- good for cells, not as appropriate for organelles
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Why are light microscopes good?
Cheap, easy to use, can be used on living material
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What are the disadvantages of light microscopes?
Magnification limited to 1500x, wavelengths limited
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What are the benefits of being able to see living specimen through a microscope?
IVF- see what you're doing to living cells. You can also see how plant cells respond to light
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What preparation do you have to do to use a light microscope?
1. Staining- coloured stains are added to the specimen so the specimen can be seen. 2. Sectioning- specimens are embedded in wax and can be cut into thin slices, less than one cell thick, without damaging the structure.
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How is the transmission electron microscope preparation different to the light microscope preparation?
The specimen is covered in lead salts or gold to help focus the electron beam.
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How do transmission electron microscopes work?
Use electromagnets to focus a beam of electrons through the specimen, the denser parts of the cell absorb more electrons so make it look darker.
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Why are TEM's good?
They have a high resolution, and give a good idea of the internal structure.
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What are the disadvantages of TEM's?
They are expensive and difficult to use and artefacts can be created.
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What are artefacts?
False features made by the fixing process.
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What's the equation for magnification?
ACTUAL SIZE= IMAGE SIZE/MAGNIFICATION
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What's a micrometre?
0.000 001m
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What's the role of carbohydrates?
Energy storage and supply, structure.
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What's the role of proteins?
Structure, transport, enzymes, antibodies, most hormones.
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What's the role of lipids?
Membranes, energy supply, thermal insulation, protective layers/padding, electrical insulation in neurones (myelin sheath), some hormones (eostrogen).
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What's the role of vitamins and minerals?
Form parts in some molecules and take part in some metabolic reactions, some act as coenzymes or enzyme activators.
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What's the role of nucleic acids?
Information molecules, carry instructions for life.
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What's the role of water?
Takes part in many reactions, support in plants, solvent/medium for most metabolic reactions, transport.
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What's metabolism?
The sum total of all chemical reactions in the body.
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What's a catabolic reaction?
A breaking down reaction, e.g. digestion, respiration.
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What's an anabolic reaction?
A building up reaction, e.g. protein synthesis, photosynthesis.
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What's ATP?
Andenosphine triphosphate is produced by almost all living things in their cells in the mitochondria. It stores energy in its phosphodiester bonds.
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Why is H20 the universal solvent?
It is polar because of its shape so the oxygen side holds the negative charge and the hydrogen side holds the positive side, this means water can dissociate ionic compounds into their positive and negative ions.
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What's carbohydrate monomer and polymer?
Monomer- monosaccharides. Polymer- polysaccharides.
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What's proteins monomer and polymer?
Monomer- amino acids. Polymer- polypeptides and proteins.
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What's nucleic acids monomer and polymer?
Monomer- Nucleotides. Polymer- DNA and RNA.
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What happens in condensation reactions?
A water molecule is released, a new covalent bond is formed, a larger molecule is formed by the bonding together of smaller molecules.
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What happens in an hydrolysis reaction?
A water molecule is used, a covalent bond is broken, smaller molecules are formed by the splitting of a larger molecule.
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What's division of labour?
Each type of organelle has a specific role within the cell, the different organelles work together, each contributing its part to the survival of the cell.
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What are the 7 characteristics of living things?
Movement, respiration, sensitivity, nutrition, excretion, reproduction and growth.
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What are the organelles responsible for movement and stability in cells?
Cytoskeleton, flagella (undulipodia) and cilia, vesicles and vacuoles, plant cell walls.
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What are the organelles surrounded by membranes?
Nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, chloroplasts, lysosomes.
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What are the organelles without membranes surrounding them?
Ribosomes, centrioles.
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What's the test for cellulose?
Add schlutze's solution to the sample, it will turn purple if the cellulose is present.
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What's the test for starch?
Add iodine, the iodine will slip into the amylose coil of the starches and turn the substance back-blue.
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What are the elements that make up amino acids?
Carbon, nitrogen, oxygen and hydrogen.
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What's a glycosidic bond?
The covalent bond formed when carbohydrate molecules are joined together in condensation reactions.
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What kind of glycosidic bond is in cellulose?
Beta, 1,4
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What kind of glycosidic bond is in starch?
Alpha, 1,4
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Card 4

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What are the disadvantages of light microscopes?

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