Which type of microscope would be best to use to observe each of the following?
a. a stained bacterial smear
b. unstained bacterial cells: the cells are small, and no detail is needed
c. unstained live tissue when it is desirable to see some intracellular detail
d. a sample that emits light when illuminated with ultraviolet light
e. intracellular detail of a cell that is 1μm long
f. unstained live cells in which intracellular structures are shown in color

Question

Which type of microscope would be best to use to observe each of the following?

a. a stained bacterial smear

b. unstained bacterial cells: the cells are small, and no detail is needed

c. unstained live tissue when it is desirable to see some intracellular detail

d. a sample that emits light when illuminated with ultraviolet light

e. intracellular detail of a cell that is 1μm long

f. unstained live cells in which intracellular structures are shown in color

Accepted Answer

Hi everyone. And welcome back. Our next question says which of the following statements about phase contrast microscopy is false. A it can visualize unstained samples. B it can allow visualization of intracellular structures. C it can excite fluorescent molecules in the sample or D all of the above. So even if we can't remember right away, what phase contrast microscopy is, we might be able to pick out our false statement just based on the thing that kind of sticks out as being different. And that's choice C it can excite fluorescent molecules because this is a false statement. Although I need to be careful, I'm going to put a little dot To note it as being false because I do have that answer choice. D all of the above. There's a possibility all of them could be false. So before I pick my final answer, I need to evaluate the other choices. But fluorescent molecules are excited during fluorescence microscopy which involves either labeling certain molecules with fluorescence or introducing fluorescent molecules into a sample and then exciting those fluorescent molecules with specific wavelengths of light. And that's specifically the tool used in fluorescence microscopy. These contrast microscopy in or by contrast, uses different light sources. So a direct light source but also reflected light refracted light and diffracted light, taking advantage of the different refractive indexes of different structures to be able to visualize unstained samples. So usually we use staining to sort of highlight the contrast and allow us to see different cellular structures. But in phase contrast microscopy, you take advantage of these different light phases to highlight those contrasts and see structures. So choice A it can visualize unstained samples is true. A phase contrast microscopy. And this is very important because it means that you can visualize living organisms. You don't need to stain them, you don't need to fix them things that involve killing a living organism. You can see living organisms, living cells under a microscope. So choice a being true is not our answer that also lets us eliminate choice D all of the above since we have at least one true statement and say that choice C is definitely the answer. But to be thorough, let's look at Choice B, it says it can allow visualization of intracellular structures. Well, this is also true. These different light sources take advantage as I said of those different refractive indices to highlight the contrast in the different in intercellular structures and shapes so that you can see them even without that staining. So Choice B cannot be our answer as it's a true statement. So once again, the false statement, when talking about phase contrast microscopy is choice C it can excite fluorescent molecules in the sample. See you in the next video.

Verified Solution

Key Concepts

Types of Microscopes

Staining Techniques

Resolution and Magnification