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Exercise 2.2: Microscopy Now that you have made your culture media, you want to observe your HeLa cells' morphology, but they're too small to see! What do you do? Light microscopes use visible light and lenses to magnify small things (well, how convenient!). One of the largest human cells is the ovum (egg); it is 0.1 mm and can probably be seen with the naked eye, while one of the smallest cells, the red blood cell, is 8 µm. Your HeLa cells are approximate 40 µm and by comparison the SARS-CoV-2 virus is only 120 nm in diameter! Lenses have magnifying ability as well as resolving power, an ability to distinguish objects that are very close together, which is defined as the minimum distance by which those objects can be viewed as separate. This provides clarity, also known as resolution, and is what allows us to see detail. Two microscopes may give the same magnification, but the clarity of images provided by one may be better due to the superior resolving power, which in turn is a function of the quality of the lens. While we want the value of magnification to be large, we want the value of resolving power to be small. Unaided, the human eye can distinguish two objects as separate from each other when they are at least 0.1 mm apart. The best light microscopes can resolve parts of a specimen that are about 0.2 µm apart! There are different types of light microscopes each with benefits for specific application. You may be familiar with the common compound light microscope (Figure 6a), that has two lenses and a stage for placing a slide of a specimen. In a compound microscope, a bright background is created; for this reason, it is called a bright-field microscope. This does not allow for much contrast between the background and live cell imaging is difficult. A phase-contrast microscope increases contrast in the image by using an optical technique that amplifies phase shifts of light that occur due to differences in refractive index; this allows for many cell structures to become visible (Figure 6b). Finally, there are microscopes that can detect fluorescence in a cell by using a much higher intensity light; small molecules present can be detected by using specific fluorescent tags. For example, a confocal microscope, a laser beam is used to scan across the specimen in successive sections; a computer is then used to construct a 3-dimensional image from the scans (Figure 6c). Transmitted Light Techniques in Live-Cell Imaging Brightfield (a) (b) (c) Figure 6. Types of light microscopy. a- brightfield, b-phase contrast, c-confocal Sources: a- zeiss-campus.magnet.fsu.edu, b & c-olympus.lifescience.com 7. What cell structure(s) are visible in each type of microscopy (Figure 6)? 8. Which type of microscopy would you choose to observe your cells before you infect them? Provide your reasoning. 9. If you looked at your cells again after infecting them with SARS-CoV-2, would one of these microscopy types allow you to visualize the virus? Why or why not?

Exercise 2.2: Microscopy
Now that you have made your culture media, you want to observe your HeLa cells' morphology, but they're too small to see! What do you do?
Light microscopes use visible light and lenses to magnify small things (well, how convenient!). One of the largest human cells is the ovum (egg); it is 0.1 mm and can probably be seen with the naked eye, while one of the smallest cells, the red blood cell, is 8 µm. Your HeLa cells are approximate 40 µm and by comparison the SARS-CoV-2 virus is only 120 nm in diameter!
Lenses have magnifying ability as well as resolving power, an ability to distinguish objects that are very close together, which is defined as the minimum distance by which those objects can be viewed as separate. This provides clarity, also known as resolution, and is what allows us to see detail. Two microscopes may give the same magnification, but the clarity of images provided by one may be better due to the superior resolving power, which in turn is a function of the quality of the lens. While we want the value of magnification to be large, we want the value of resolving power to be small. Unaided, the human eye can distinguish two objects as separate from each other when they are at least 0.1 mm apart. The best light microscopes can resolve parts of a specimen that are about 0.2 µm apart!
There are different types of light microscopes each with benefits for specific application. You may be familiar with the common compound light microscope (Figure 6a), that has two lenses and a stage for placing a slide of a specimen. In a compound microscope, a bright background is created; for this reason, it is called a bright-field microscope. This does not allow for much contrast between the background and live cell imaging is difficult. A phase-contrast microscope increases contrast in the image by using an optical technique that amplifies phase shifts of light that occur due to differences in refractive index; this allows for many cell structures to become visible (Figure 6b). Finally, there are microscopes that can detect fluorescence in a cell by using a much higher intensity light; small molecules present can be detected by using specific fluorescent tags. For example, a confocal microscope, a laser beam is used to scan across the specimen in successive sections; a computer is then used to construct a 3-dimensional image from the scans (Figure 6c).
Transmitted Light Techniques in Live-Cell Imaging
Brightfield
(a) (b) (c)
Figure 6. Types of light microscopy. a- brightfield, b-phase contrast, c-confocal
Sources: a- zeiss-campus.magnet.fsu.edu, b & c-olympus.lifescience.com
7. What cell structure(s) are visible in each type of microscopy (Figure 6)?
8. Which type of microscopy would you choose to observe your cells before you infect them? Provide your reasoning.
9. If you looked at your cells again after infecting them with SARS-CoV-2, would one of these microscopy types allow you to visualize the virus? Why or why not?

$Exercise 2.2: Microscopy Now that you have made your culture media, you want to observe your HeLa cells' morphology, but they're too small to see! What do you do? Light microscopes use visible light and lenses to magnify small things (well, how convenient!). One of the largest human cells is the ovum (egg); it is 0.1 mm and can probably be seen with the naked eye, while one of the smallest cells, the red blood cell, is 8 µm. Your HeLa cells are approximate 40 µm and by comparison the SARS-CoV-2 virus is only 120 nm in diameter! Lenses have magnifying ability as well as resolving power, an ability to distinguish objects that are very close together, which is defined as the minimum distance by which those objects can be viewed as separate. This provides clarity, also known as resolution, and is what allows us to see detail. Two microscopes may give the same magnification, but the clarity of images provided by one may be better due to the superior resolving power, which in turn is a function of the quality of the lens. While we want the value of magnification to be large, we want the value of resolving power to be small. Unaided, the human eye can distinguish two objects as separate from each other when they are at least 0.1 mm apart. The best light microscopes can resolve parts of a specimen that are about 0.2 µm apart! There are different types of light microscopes each with benefits for specific application. You may be familiar with the common compound light microscope (Figure 6a), that has two lenses and a stage for placing a slide of a specimen. In a compound microscope, a bright background is created; for this reason, it is called a bright-field microscope. This does not allow for much contrast between the background and live cell imaging is difficult. A phase-contrast microscope increases contrast in the image by using an optical technique that amplifies phase shifts of light that occur due to differences in refractive index; this allows for many cell structures to become visible (Figure 6b). Finally, there are microscopes that can detect fluorescence in a cell by using a much higher intensity light; small molecules present can be detected by using specific fluorescent tags. For example, a confocal microscope, a laser beam is used to scan across the specimen in successive sections; a computer is then used to construct a 3-dimensional image from the scans (Figure 6c). Transmitted Light Techniques in Live-Cell Imaging Brightfield (a) (b) (c) Figure 6. Types of light microscopy. a- brightfield, b-phase contrast, c-confocal Sources: a- zeiss-campus.magnet.fsu.edu, b c-olympus.lifescience.com 7. What cell structure(s) are visible in each type of microscopy (Figure 6)? 8. Which type of microscopy would you choose to observe your cells before you infect them? Provide your reasoning. 9. If you looked at your cells again after infecting them with SARS-CoV-2, would one of these microscopy types allow you to visualize the virus? Why or why not?$

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