y Transporter proteins z. Vibrio Recognize the metric units that are used for mi
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y Transporter proteins z. Vibrio Recognize the metric units that are used for microorganisms. For example, if a microbe measures 10 um in length, how long is it in nanometers? 2. 3. Describe the path of light in a compound microscope and of electron in an electron microscope 4. How do magnification, resolution, and contrast affect microbial observations in microscopy? 5. Distinguish bright-field, dark-field, phase-contrast, and fluorescence microscopy. What are their uses? 6. Why do electron microscopes have greater resolution than light microscopesi? 7. For what is TEM used? SEM? Scanned-probe microscopy? 8. Explain the purpose of simple staining. How do you prepare microbial species for staining? Why is fixing necessary for most staining 9. procedures? 10. Describe the Gram staining procedure. Why is the Gram stain so useful? 11. Which stain would be used to identify microbes in the genera Mycobacterium and Nocardia? Why? 12. What are the benefits of using fluorescent dyes and tags? 13. What is each of the followin: capsule stain, fagel la stain, endospore stain? 14. Describe similarities and differences between Eukaryotic and Prokaryotic cells 15. Identify the basic shapes of bacteria and understand the terms used to describe the shapes and arrangement of bacterial cels. Book Pro F3 F4 F5 F6 F7 F8 F9Explanation / Answer
2)metric units that are used for micro organisms are as follows:
1 meter = 10 0 m.
Decimeter = 1/10 = 1dm=0.1m=10-1m
Micrometer= 1/1000000 = 0.0000001 m = 10-6m
Nanometer= 1/1000000000=0.0000000001 m = 10-9m
Typically virus measures about 100 micrometer, 10 times smaller than a typical bacteria which is at least 10 times smaller than plant or animal cell.An object must measure about 100 micrometer to be visible without a microscope.
3)Compound microscope is also called bright field microscope which is a ordinary microscope.When a ray of light passes from one medium to another, refraction occurs, the ray is bent at the interface. The reflective index is a measure of how greatly a substance slows the velocity of light; the direction and magnitude of bending is determined by the reflective indexes of the two media forming the interface.Thr specimen image rays get refracted when it enters and exits the objective lens and the eye piece. The objective lens forms an enlarged real image within the microscope, and the eyepiece lens further magnifies the primary image. From start to the end the ray starts from a tiny point and it gets magnified at the end point at the human eyes.So, when one looks into a microscope, the enlarged specimen image called the virtual image appears to lie just beyond the stage about 25 cm away. The light ray gets refracted at the base of the index of refraction of the lens. Here the magnifying power of microscope is the linear magnificating of the objective times the angular magnification of the eye piece. The total magnifications is calculated by multiplying the objective and eyepiece magnifications together.
The basic principle in modern transmission electron microscope is complex and sophisticated. A heated tungsten filament in the electron gun generates a beam of electrons that is focused on the specimen byvthe condenser.Since electrons cannot pass through a glass lens , doughnut shaped electromagnets called magnetic lenses are used to focus the beam. The column containing the lenses and specimen must be under high vaccum to obtain a clear image because electrons are deflected by collisions with air molecules. The specimen scatters electrons passing through it, and the beam is focused by magnetic lenses to form an enlarged, visible image if the specimen on a flourescent screen. A denser region in the specimen scatters more electrons and therefore appears darker in the image since fewer electrons strike that area of the screen. In contrast, electron transparent region are brighter. The screen can also be moved aside and the image captured on photographic film as a permanent record.
4)Magnification is the apparent increase in the size of an object as viewed through a microscope.
Objective ( lens near the specimens) magnifications typically are 4X,10X and 40X.
Ocular ( eye piece) magnification is typically 10X
Total magnification = magnifications of objective * magnifications of ocular.
Resolution is the relative clarity of the microscope image. The resolution of the image is principle controlled using the coarse and fine focus knobs. However , intensity of light, controlled by the substage diaphragm also has a dramatic effects upon the resolution of the image.
Contrast is the difference in intensity between an object and it's surroundings. Contrast adjusted using the substage diaphragm. In general, diaphragm should be nearly closed under the scanning (4X) objective , and opened to increase the brightness as we switch to higher power objectives.
4) the ordinary microscope is called a bright field microscope because it forms s dark image against a brighter background. A light source , either is a mirror or an electric illuminator, us located in the base. Two focusing knobs, the fine and coarse adjustment knobs, are located on the arm and can move either the stage or the nose piece to focus the image.
The dark field microscope: only light that has been reflected or refracted by the specimen forms an image. The field surrounding a specimen appears black, while the object itself is brightly illuminated. Because the background is dark , this type of microscope is called dark feild microscope. It is used to identify bacteria like the thin and distinctively shaped Treponema pallidum .
The phase contrast microscope: it converts slight difference in refractive index and cell density into easily detected variation s in light intensity and is an excellent way to observe living cells.
Flourescence microscope: it exposes a specimen to UV, violet or blue light and forms an image of the object resulting flourescence light.
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