Ch 2 Microscopy

Question 1

What were the first microscopes like?

Answer 1

They were simple microscopes that allowed people to see microorganisms. Through these microscopes, light was passed through only one lens.

Question 2

What types of things could be seen with the first microscopes?

Answer 2

microbes like bacteria, protozoa, and single-celled organisms.

Question 3

What does resolution mean?

Answer 3

ability to differentiate that 2 points are separate.

Question 4

What factors determine resolution?

Answer 4

wavelength and numerical aperture

Question 5

How does wavelength affect resolution?

Answer 5

shorter wavelengths have a greater resolving power, allowing people to see smaller objects.

Question 6

How does numerical aperture affect resolution?

Answer 6

measures the ability of a lens to gather light; the higher it is, the better the resolution of an object is

Question 7

Why is immersion oil important?

Answer 7

It enhances resolution by collecting more light to strike the lens.

Question 8

What size range are “typical” eukaryotic cells?

Answer 8

Around 10 µm to 100 µm

Question 9

What size range are “typical” prokaryotic cells?

Answer 9

About 1 µm

Question 10

What size range are “typical” viruses?

Answer 10

Roughly 100 nm

Question 11

What is Bright field microscopy?

Answer 11

A compound microscope that is one of the most used types of microscope. It produces dark images of an organism on a white field. It uses staining to increase the contrast and resolution of a specimen.

Question 12

What is Dark field microscopy?

Answer 12

produces an image of a light organism on a dark field
- it does not need stains to create a high contrast and resolution image of a specimen

Question 13

Which specimen does dark field microscopy examine?

Answer 13

live, unstained specimens.

Question 14

What is phase contrast microscopy?

Answer 14

utilizes refraction and interference caused by the structures in an organism. Refraction and interference allow the production of high-resolution and contrast images.
- images are created by the alteration of wavelengths of light rays that pass through the organism

Question 15

Which specimen does phase contrast microscopy examine?

Answer 15

live specimens
Ex: endospores in prokaryotic cells and organelles in eukaryotic cells

Question 16

What is fluorescence microscopy?

Answer 16

Uses fluorochromes that absorb energy from a light source and emit it as visible light. Fluorescent probes bind to specific cell types or type of structure to create an image of an organism in bright colors against a dark field.

Question 17

Which specimen does flourescence microscopy examine?

Answer 17

spot and pinpoint disease-causing microorganisms (immunofluorescence).

Question 18

What is confocal microscopy?

Answer 18

lasers scan numerous z-planes, to create multiple high-resolution, 2-D images at a variety of depths
- These images can be used to create a three-dimensional image using a computer. Fluorescent stains increase the resolution and contrast of the images.

Question 19

Which specimen does confocal microscopy examine?

Answer 19

thick specimens both unfixed and alive

Question 20

What is electron microscopy?

Answer 20

increase the magnification and resolution of an image by using short-wavelength electron beams. They have very short wavelengths of 0.005nm with a very high resolution of 1nm. With these microscopes, people can see subcellular structures. This type of microscopy cannot be used on living material.

Question 21

What is scanning electron microscopy?

Answer 21

used to view surfaces of specimens
- a beam of electrons is used to knock electrons off the surface of the microorganism
- three-dimensional, highly detailed images

Question 22

What is transmission electron microscopy?

Answer 22

Electron beams that pass through an organism are used to examine small images. The specimens have to be extremely thin and dehydrated to see the internal structures of the specimen.

Question 23

What is probe microscopy?

Answer 23

Very short and sharp probes that are passed over the surface of the specimen and directly interact with it are used. This type of microscopy does not use light or electrons. It can be used to view atoms and surfaces.

Question 24

What is scanning tunneling probe microscopy?

Answer 24

Pictures the structure of surfaces at a resolution where atoms can be seen. The process involves moving a probe horizontally above a surface and measuring the variations in the current. This type of microscopy works best with conducting materials

Question 25

What is atomic force microscopy?

Answer 25

It has a constant current, but it measures variations in the height of the thin probe tip as it is passed just above the specimen. With a resolution at the atomic level, images of the surface of the specimen are produced. Atomic force microscopy is easier to use with nonconducting specimens.

Question 26

What microbes/structures can we NOT see with our brightfield microscopes?

Answer 26

Viruses