Karteikarten
Lab Quiz #1
Karten in diesem Stapel (18)
- 1Microscopean invaluable tool used for observing objects that can not be seen by the naked eye; enables us to view the ultrastructure (fine detail) of organisms, cells, and tissues.
- 2compound light microscopemagnifies objects from 40 to 1000 times its original size
specimens must be either small objects of very thinly cut sections of an object; translucent allowing light to be transmitted through them - 3dissecting (stereoscopic) microscopemagnifies objects from 4 to 50 times
specimens are usually opaque - 4Normal Procedure to prepare a specimen for most staining protocolsallow the organisms to dry to a glass slide; pass the slide through the Bunsen burner flame in order to fix the organisms to the slide
- 5Problems with this procedure and whyThis procedure does not allow one to visualize the cells in their natural state. The size and shape of the cell may become distorted. Also, heat-fixing removes the water from the cell which affects the size of the cell when viewed under the microscope
- 6Pros to Negative Stainingallows one to view living organisms that have not been heat-fixed to a slide; allows one to visualize organisms or parts of organisms, such as a capsule, which may not readily take up stains
- 7Negative Staining characteristicsThe background is filled with a stain (such as India ink or nigrosin) while the organisms remain clear, unstained objects that stand out clearly against this dark background.
- 8The "why" behind the cells appearing clear when stainedThese stains (negative stains) do not penetrate the bacterial cells due to the repulsion between the negative charge of the stains and the negatively charged bacterial cell.
- 9Two different methods to prepare negative stainsa suspension of bacterial cells is emulsified in a drop of nigrosin (India ink) and covered with a cover slip (wet mount) or allowed to air dry (smear)
- 10Most microorganisms appear ______ when viewed through a ___________ _______ microscope.colorless; brightfield light
- 11Most common method method of allowing visualization of microorganisms under a microscope is to ...stain, or color them.
- 12Staining _________ to the microorganisms so that various structures can be observedimparts color
- 13How to prepare a bacterial smearA drop of liquid bacterial culture or a drop of water and a portion of a bacterial colony is spread over the surface of the slide
- 14Important facts about preparing the bacterial smearone loopful of liquid bacterial culture usually provides sufficient bacteria for easy viewing
REMEMBER 1 bacterial colony = millions of individual bacteria
When mixing water with the bacteria only a small drop of water is needed - 15Why is only a small amount of water needed?the smears are air-dried, the more liquid, the longer the smear will take to dry
- 16When mixing the bacteria with the water to create the smear...avoid overmixing because this can lead to inaccurate bacterial cell patterns (chains may appear as clumps and vice versa)
- 17Once the smear has air-dried, the next step is toheat-fix the slide
- 18Heat-fixThe air-dried smear is briefly passed through the Bunsen burner flame 2 or 3 times.
Informationen
- Beschreibung
- This includes exercises 2, 6, 7, and 8 which are entitled The Compound Light Microscope; The Negative Stain; Preparing a Bacterial Smear; and The Simple Stain
- Erstellt von
- Calla Frederiks
- Aufrufe
- 12
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