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The Microscope Zacharias Janssen is to be credited for i.docx
- 1. The Microscope Zacharias Janssen is to be credited for inventing the first truly compound microscope Microscope What is a microscope?It is a tool or instrument often used in laboratories to aid in viewing organisms that cannot be seen with an unaided eye Types of microscope Biologist often used different microscope Compound light microscope Dissection microscope Scanning electron microscope(SEM) Transmission electron microscope(TEM) but of all, the compound light microscope is what we shall be using Dissecting Vs. Compound light microscope Scanning Vs. Transmission electron Microscope
- 2. Microscope Compound light microscope is simply a microscope that has at least two magnifying lenses (the oculars and the objectives)Binocular microscope possess two eyepieces (what we shall be using in the lab)Monocular microscope possess one eyepieces Bi = two mono = one Microscopes Electron microscope magnifies the specimen 1000X larger than the light microscopeThe Dissecting microscope on the other hand has a low magnification power (7X to 30X). It is used to view large objects * Microscope There are a variety of light microscope but each differs by the emission of light through the specimen that is viewed Phase contrast Darkfield Polarizing UV Terms Bright Field: illumination, sample contrast comes from absorbance of light in the sample.
- 3. Cross polarized light: illumination, sample contrast comes from rotation of polarized light through the sample. TermsDark Field: illumination, sample contrast comes from light scattered by the sample.Working distance: distance between the specimen and the objective lens ( is this distance greater with the 40x or the 10x objective ? Ans: 10x ) Phase Contrast: illumination, sample contrast comes from interference of different path lengths of light through the sample. labelsLight source, a light or a mirror (7)Diaphragm and condenser lens (8)Objective (3)Ocular lens (eyepiece) (1)In addition the vast majority of microscopes have the same 'structural' components:Objective turret/ nosepiece (to hold multiple objective lenses) (2) LabelsStage (to hold the sample) (6)Focus wheel to move the stage (4 - coarse adjustment, 5 - fine adjustment) Stage adjustment knobs (9) Terms used when dealing with a microscope The headIt supports the two sets of magnifying lenses
- 4. The Oculars (eyes)It is the lenses used to view the specimen.Located on the eyepieceHas a magnification of 10X Microscope Interpupillary distanceThis is the distance between the eyepiece on a binocular microscopeIt can be adjusted to suit your eyes Field of view “FOV”the diameter of the circle of light that you see when looking into a microscope Microscope (cont..) ObjectivesThese are the four lenses on the revolving nosepieceFour types exist: 4x , 10x , 40x , 100x 4X : the scanning lens 10X: the intermediate lens 40X: the high power lens 100X: the oil immersion lens Microscope(cont..) The ArmThe part of the microscope that connects the tube to the base The Condenser lensit focuses the light onto the specimen. It can be located in or below the stage Microscope (cont..) The Adjustment Knobused to adjust the height of the condenser
- 5. Iris DiaphramIt controls the amount of light that passes to reach a specimen StageThe flat plate where the slides are placed for observation. Microscope (cont..) Stage ClipsClips on the stage used to hold the slide in place Stage Adjustment KnobFound on mechanical stageAids in moving the stage left to right or back and forth (vice versa) Microscope(cont…) Fine FocusThis is the knob used to fine tune the focus on the specimen. It is also used to focus on various parts of the specimen. Generally one uses the coarse focus first to get close then moves to the fine focus knob for fine tuning. Microscope(cont..) Coarse FocusThis is the rough focus knob on the microscope. You use it to move the objective lenses toward or away from the specimen BaseThe bottom support of the microscope How to Use a Microscope To carry a microscope, place one hand on the arm and the other on the base of your microscope
- 6. Clean the MicroscopeIt is imperative to clean the lenses of your microscope each time you use begin an experimentClean using lens paper moistened with distilled water, then again without the water How to Use a Microscope(cont..) 2. Plug in your microscope and turn on the light. 3. Begin viewing from 4X. If the lens is not at 4X rotate till you get it 4. Make sure you always clean a prepared slide before viewing it. Place it on the stage 5. While looking through your oculars,(if binocular move the lenses until to are able to view just an image of the specimen) feel free to adjust your specimen using your coarse adjustment How to Use a Microscope(cont..) 6. The correct position of your condenser is when you slowly lower the condenser until the graininess disappear. While that of the iris diaphram is when you slowly open the diaphram until the entire field of view is illuminated 7. Rotate the nosepiece using different objective lenses How to Use a Microscope(cont..) NB: do not view your specimen using the 100X objective without using immersion oil. 8. At the end of your exercise, turn off your microscope and
- 7. clean before returning it in the cabinet. ONE HAND ON THE ARM & ONE HAND ON THE BASE!!!!!! Calculations What would be the total magnification if the ocular were 10X and the objective 40X?10 x 40 = 400X Organization of Cells Prokaryotes: These are singled (one) celled organisms. Eg: bacteria. They have a diameter of approximately 1 micrometer (μm).They lack a nucleus (houses the genetic materials). Genetic material is stored in the nucleiod region (cytoplasm)They have a cell membrane, flagellum (pl. – flagella) aids in mobility.Asexual reproduction Organization of Cells (cont..) Eukaryotes: These are cells with a nucleus and membrane bound organelles Eg: plasma membrane, mitochondria, golgi apparatus, chloroplast, ER, cilia and flagella, etc. Unicellular: singled celled (can survive by itself) Aggregates: clusters of cells Colonies: A consistent and predictable # of cells Organization of Cells(cont…)
- 8. Multicellular: Large # of cells, each cells has a special function. NB: none can exist successfully without the other. Lab ExerciseLearn how to use the light compound microscope.Identify parts of light compound microscope it moves using Pseudopodia(False feet )Aggregate and Colonial Organism: Examine the prepared slide Volvox Lab ExerciseMulticellul the basic tissue types of plants and animals.Plant cells: cell wall, protoplasm,cytoplasm, central vacuole, chloroplasts, nucleusAnimal cells: Human epithelial cells ( cheek cells) Lab ExerciseTo obtain a specimen ( epithelial cell or cheek cells):1. With a clean toothpick, gently scrape the inside of your cheek several times2. Roll the scraping into a drop of water on a clean microscope slide, add a small drop of methylene blue, and cover with a coverslip . Discard the used toothpick in disinfectant3. Using the compound microscope, view the cells under high power, identify the cell membrane, nucleus, and cytoplasm. Lab Report Format: Each report should include the following: Title page:
- 9. Name, Course, Instructor Title of experiments Partner’s name (if you worked with a partner that day) Introduction (20%): Write one paragraph (at least 4-5sentences) on background and purpose of the experiment. This should be mostly in present tense format. Materials and methods (10%): Give chemicals, materials and equipment you used in past tense prose format. The methods must be presented in past tense. If your methods deviated from those listed in the lab manual be sure to give the methods you actually used in lab. Don’t begin sentences with numbers. You may divide this section of the report into subheadings. For example, “Preparation of enzyme,” “Enzyme assay,” and “Temperature and pH effects on enzyme activity” could be some of the subheadings you may include. Results (40%): Record of data, including sample calculations, images, graphs: Refer to tables in the report as Table 1, Table 2, Table 3 etc. Refer to figures in the report as Figure 1, Figure 2, Figure 3 etc. Figures may include graphs, images, drawings, chemical structures. All figures, tables, etc. are to be clearly labeled. You should explain in writing what the figures demonstrate (no interpretation/conclusions in this section!!) Discussion (30%): Give a 1-2 paragraph discussion (at least three to five sentences
- 10. each) of the scientific conclusions you drew from the experiment. Results specific to the experiment are written in the past tense and the overall conclusions you draw are written in the present tense. In this section, also give any reasons for why your experiment do not work successfully (if applicable). For example, “In our study, polyphenoloxidase oxidized catechol twice as quickly as phenol and hydroquinone. Due to the observation that all three substrates exhibited some color change it is concluded that polyphenoloxidase exhibits group specificity.” 1