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Description
Flashcards by lottieweaver, updated more than 1 year ago
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Created by lottieweaver
almost 11 years ago
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| Question | Answer |
| When did Robert Hooke develop the compound microscope? | The 1660's. |
| What is a compound microscope? | A microscope with several lenses. |
| What did Hooke use the microscope to examine and what did he see? | Slices of cork taken from beneath the bark of a tree, he saw lots of tiny chambers, like cells in a monastry. |
| Who created The Cell Theory and when was it accepted? | Schleiden and Schwann in the 1840's. |
| Who extended The Cell Theory and what did it state? | Virchow (1855) and Weismann (1880), it states that: all living things are made of cells, new cells are only formed by the division of pre-existing cells, cells contain information as instructions for growth which is passed on to new cells. |
| What is magnification? | The degree to which the size of an image is larger than the object itself. |
| What is resolution? | The degree to which it is possible to distinguish between two objects that are very close together. |
| How do light microscopes work? | Number of lenses, light passes from bulb under stage, through condenser lens, through specimen, focused through objective lens, through eyepiece lens, rotational 4 objective lenses. |
| What is the maximum magnification of a light microscope? | x1500 |
| What is the maximum resolution of a light microscope? | 200nm |
| Why are samples stained? | Chemicals bind to chemicals on or in the sample, allowing the specimen to be seen more clearly and highlight certain features. |
| Why are samples sectioned? | Specimens are embedded in wax, thin section are cut without distorting the structure, useful for soft tissue, e.g. brain. |
| What is a micrometre used to measure? | As a µm is one millionth of a metre, it is the standard unit of measurement for cells. |
| How big is the average animal cell? | 20-40 µm |
| What are nanometres used to measure? | As a nm is one thousand millionth of a metre, they are used to measure organelles and molecules. |
| What is the average width of a cell surface membrane? | 10nm |
| What is the average diameter of a ribosome? | 20nm |
| How big is the average virus? | 40-100nm long |
| What is the resolution of the human eye? | 100 µm |
| What is the resolution of an electron microscope? | 0.2nm |
| What is a graticule? | A transparent cover for the eyepiece of a microscope with a small ruler etched on it for measuring dimensions of a specimen. |
| How is magnification worked out? | Magnification = Image size/Actual size |
| How do electron microscopes work? | Generate beam of electrons, magnets focus beam onto specimen, black and white image projected. |
| What is a TEM? | Transmission electron microscope, beams pass through thin sample, the denser the sample the more difficult creating contrast, 2D image, magnification x500000. |
| What is an SEM? | Scanning electron microscope, electron beams directed at sample, bounced off, 3D view of surface, magnification of x100000. |
| What are the advantages of electron microscopes? | Resolution 0.2nm, detailed images of organelles, SEM produces 3D images to reveal contours and cellular and tissue arrangements. |
| What are the limitations of electron microscopes? | Electron beams are deflected by air so samples have to be in a vacuum, very expensive, requires skill and training to prepare and use. |
| What are the 7 characteristics of living things? | Movement, respiration, sensitivity, nutrition, excretion, reproduction and growth. |
| What are organelles? | The structures inside a cell, e.g. the nucleus, they make up the ultrastructure. |
| What is the division of labour? | When each organelle has a specific role within the cell. |
| What is the cytoskeleton? | A network of protein fibres used to keep the cell's shape stable by providing an internal framework, they also move organelles around inside the cell. |
| What are microtubules? | Cylinders, 25nm in diameter, made of protein called tubulin, they waft microorganisms through liquid or waft liquid past the cell, using ATP. |
| What are flagella/undulipodia and cilia? | Hair-like extensions that stick out from the cell. They are made of a cylinder that contains 9 microtubules in a circle, with 2 microtubules in a central bundle. |
| Which are longer - undulipodia or cilia? | Undulipodia. |
| What are vesicles? | Membrane-bound sacs found in cells used to carry substances around cells. |
| What are vacuoles for in plant cells? | They maintain cell stability, they are filled with water to make the cell turgid, this is especially important in non-woody plants. |
| What are plant cell walls made of? | Cellulose, a carbohydrate polymer made of glucose subunits, it is a sieve-like network that makes the wall strong, the whole cell is held firm by turgor pressure. |
| What is the structure of the nucleus? | Largest organelle, surrounded by a nuclear envelope, two membranes with fluid between, nuclear pores in envelope, nucleolus inside. |
| What is the function of the nucleus? | Houses genetic material, chromatin consists of DNA and protein, instructions for making proteins, makes RNA and ribosomes. |
| What is the structure of endoplasmic reticulum? | Flattened membrane-bound sacs called cisternae, rough ER is studded with ribosomes, smooth ER is not. |
| What is the function of ER? | RER transports proteins made on ribosomes, SER makes lipids. |
| What is the structure of the golgi apparatus? | Stack of membrane-bound flattened sacs. |
| What is the function of the golgi apparatus? | Receives proteins from ER and modifies them, may add sugar molecules, packages into vesicles to be transported. |
| What is the structure of the mitochondria? | Spherical/oval, two membranes separated by fluid-filled space, inner membrane folded to form cristae, central part is the matrix. |
| What is the function of the mitochondria? | Produces ATP during respiration (adenosine triphosphate). |
| What is the structure of chloroplasts? | Only in plant cells and some protoctists, two membranes separated by fluid-filled space, flattened membrane sacs called thylakkoid (granum/grana) chlorophyll molecules. |
| What is the function of chloroplasts? | The site of photosynthesis in plant cells, light energy used to drive reaction, carbohydrate molecules made from carbon dioxide and water. |
| What is the structure of lysosomes? | Spherical sacs surrounded by a single membrane. |
| What is the function of lysosomes? | Contain powerful digestive enzymes, break down materials, e.g. white blood cell/sperm cell. |
| What is the structure of ribosomes? | Tiny organelles, some free in cytoplasm, some bound to ER, consists of two subunits. |
| What is the function of ribosomes? | The site of protein synthesis, coded information (mRNA) from nucleus is used to assemble proteins from amino acids. |
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