CH1 and Appendix

Question 1

Latin for Small Room

Answer 1

Cellulus

Question 2

Not made of many cells

Answer 2

Acellular or Unicellular

Question 3

Greek for a hollow place

Answer 3

cyt- (ex. cytoplasm; cytosol)

Question 4

Three tenants of cell theory

Answer 4

1. All living organisms are composed of one or more cells.
2. The cell is the most basic unit of life.
3. All cells arise from pre-existing, living cells, by biogenesis.

Question 5

Typical cell sizes for prokaryotic and eukaryotic cells:

Answer 5

Eukaryotic cells - 10-100 micrometers in diameter (if spherical).
Prokaryotic cells - 1-10 micrometers in length (or diameter for cocci).

Question 6

Why can’t cells be very large?

Answer 6

Surface area to volume ratios need to be small.

Question 7

What are some characteristics of particularly large cells?

Answer 7

They are very long and not spherical (muscle cells), or large spheres with a very slow metabolism (chicken egg).

Question 8

The larger the sphere the _____ surface area it has per unit of volume.

Answer 8

Less (smaller surface area to larger volume)

Question 9

What is the minimum distance at which you can still distinguish two points as separate entities (as opposed to looking like one)?

Answer 9

200 nanometers. Any two objects closer together than that will look as one object under the microscope.
**It has nothing to do with the size of the object itself and everything to do with the distance between two objects.

Question 10

What is the term for the minimum distance that can separate two points that still remain identifiable as two points?

Answer 10

Resolution

Question 11

Ordinary light microscopy is also referred to as what?

Answer 11

Bright field microscopy

Question 12

What are some requirements for normal light microscopy? ~

Answer 12

Generally require stain/dye.

~Traditional stains require the specimen to be dead.

Question 13

How do stains for light microscopy generally adhere?

Answer 13

Using attractive electrostatic interactions.

Question 14

What kind of a stain would you use for DNA?

Answer 14

Positive stain. DNA is negatively charged, therefore a positive stain would be attracted.

Question 15

What are stains that are used with living organisms?

Answer 15

Vital stains.

Question 16

How good are vital stains?

Answer 16

Not the best… They tend to be very faint.

Question 17

What are some alternatives to bright field microscopy that do not require stain?

Answer 17

Phase contrast microscopy

Differential interference contrast (DIC)/Nomarski optics

Question 18

What type of microscopy creates light/dark details based on density?

Answer 18

Phase contrast microscopy

Question 19

How can you recognize phase contrast?

Answer 19

Halos around the cells (artifacts of the microscope).

Question 20

What can you use to accurately stain specific areas?

Answer 20

Antibodies.

Question 21

What is a variation of immunofluorescence in which you only see what is in focus on the microscope?

Answer 21

Confocal microscopy.

Question 22

What type of microscopy uses density gradients to provide contrast?

Answer 22

Differential interference contrast (DIC).

Question 23

How can you recognize DIC?

Answer 23

Light and dark areas are based on density. Causes false shadows, but there are no artifacts.

Question 24

Why would you rather choose an alternative to bright field than using stained specimens in bright field?

Answer 24

With the alternatives, the cells can be alive.

Question 25

How specific are traditional stains?

Answer 25

Not very… Positively charged stains will stain ANYTHING negatively charged, not necessarily just what you wanted stained.

Question 26

What kind of technique can you use to determine if a specific molecule is present in a sample?

Answer 26

Immunofluorescence.

Question 27

What procedure is used in immunofluorescence?

Answer 27

(Pretend we’re looking for aflatoxin in a sample) 1. Inject aflatoxin into animal (rabbit)
2. Animal produces “primary” antibodies (proteins) that bind to aflatoxin specifically.
3. Harvest primary antibodies from rabbit blood.
4. Apply to sample on slides.
–>The antibodies will bind to any aflatoxin in the sample.
Visualization: Apply fluorescent secondary antibodies. (Prepared by injecting another species, like a goat, with the rabbit antibodies. The secondary antibodies made against the primary antibodies are then modified with something fluorescent, and then used on the sample.)

Question 28

What is created in the view of the microscope when using confocal microscopy?

Answer 28

Optical sections. (Optical, because they’re not real sections, just in the view of the microscope).

Question 29

What does electron microscopy use to view specimens?

Answer 29

Electrons moving as waves.

Question 30

What is the resolution of electron microscopes?

Answer 30

2.5-6 nm resolution (Can tell two objects are separate if they’re at least that distance apart).

Question 31

Why is the resolution of electron microscopes better than light microscopes?

Answer 31

Electrons have a shorter wavelength than visible light.

Question 32

What does TEM stand for?

Answer 32

Transmission electron microscopy.

Question 33

How does TEM work?

Answer 33

Ultrathin sliced sections are infiltrated with liquid plastic, then stained with metals. Electrons are then shot through the section and form an image.

Question 34

The organelles that take up metal reflect electrons and create dark areas in TEM are called…?

Answer 34

Electron dense regions.

Question 35

How is a SEM image different than a TEM image?

Answer 35

SEM creates a 3D image, while TEM is differentiated by density.

Question 36

What are some disadvantages of SEM and TEM?

Answer 36

The picture is in black and white (electrons are only one wavelength, so no color). Also, the specimen is in a vacuum, so it must be dead.

Question 37

What is the process of freeze fracturing?

Answer 37

Coat specimen with metal from an angle to produce some false shadowing when shot with electron microscopy.

Question 38

How is SEM coating accomplished?

Answer 38

Coating is referred to as “sputter coating”. An ionized gas of gold moves between electrodes to coat the specimen.