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General Biology I Lab Practical Notes 1-6

General Biology I Lab Practical Notes 1-6 - Ann Halmi...

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Ann Halmi General Biology I Lab Practical Notes 1-6 [Section B6 – 9:00 AM in Room 140] LAB 1: Cell Structure –How to use a compound microscope What you are able to observe with a microscope depends largely on your ability to use it properly Carry the microscope in an upright position Carry the microscope with both hands to grasp the arm and support the base Always leave the microscope on the lowest-power objective when finished Cleans lens surface only with lens paper Always begin examining an object by using the lowest-power objective (on many microscopes this is the scanning lens) While changing magnification be sure they will not strike any object place on the stage Commercially prepared slides vs. “wet mounts” Always focus with the scanning lens With the high power objective in position, focus with the fine adjustment only Never remove a slide from beneath the high power objective; switch back to low power first –Main parts of a cell There is no such thing as a typical cell “Representative” Eukaryotic Cells – Contains a true nucleus with multiple chromosomes, have several types of specialized organelles, and have a differentially permeable cell membrane, includes protozoa, fungi, algae, plants, and invertebrate and vertebrate animals o Plant cell with chloroplasts ( Elodea leaf cell) o Plant cell without chloroplasts ( Onion epidermis) o Animal cell ( Human cheek cell) o Single-celled organism ( Euglena – Often called “plant-like” because it is photosynthetic) Prokaryotic Bacterial Cells – Lack a membrane bound nucleus, instead containing a single strand of nucleic acid, contain few organelles, rigid or semi-rigid cell wall provides shape to the cell outside the plasma membrane, includes bacteria and archaea o Bacteria –Parts of a microscope Nosepiece – Turn for objectives Eyepiece (ocular) – 10x
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Arm – Hold microscope Objectives o Scanning Lens (4x) o Low Power (10x) o High Power (40x) Specimen Holder – Positions the slide to be examined Stage Controls – Moves slide Condenser o Should always be close to the slide o Opens and closes the field o Lens system located immediately below the stage o Two Important Functions: Focuses the light on the specimen (should be close to the side you are viewing) and the condenser diaphragm determines the contrast and resolution (resolving power) of what you are seeing Condenser Diaphragm Adjustment Lever o Closed – Maximized for contrast, easier to see a clear object, but loses detail (resolution) o Open – Lose contrast (harder to see) but you can see more detail o Should constantly be opened and closed to adjust for contrast or resolution Knob to Adjust Condenser Height Coarse Adjustment (towards) – Raises/lowers the stage Fine Adjustment (away) – Sharpens focus Lamp – Light source Base On/Off Switch Intensity Adjustment (dial) – Brightness of light Power Cord
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