EXAM #2

Question 1

What is magnification?

Answer 1

The ratio of an object’s image size to real size ; produce an image of an object at a larger scale than it’s actual size

Question 2

What is resolution?

Answer 2

The minimum distance between two distinct points where they can distinguished ; ability to distinguish two objects from each other

Question 3

What is contrast?

Answer 3

Accentuates the differences in parts of the sample (makes things look lighter / darker ; Lightness or colorless or transparent specimens relative to the darkness in the background. (Difference in light intensity.)

Question 4

What are the types of microscopy?

Answer 4

Light microscopy & Electron microscopy

Question 5

Light microscopy

Answer 5

Uses lenses to bend light that has passed through a specimen in a way that magnifies the image

Question 6

Electron microscopy

Answer 6

Uses a focused beam of electrons that passes through a specimen or onto its surface

Question 7

Types of electron microscopy

Answer 7

Scanning (SEM) & Transmission (TEM)

Question 8

Scanning (SEM)

Answer 8

Produces images of a specimen’s surface structure (topography), with a focused beam of electrons. (Electrons bounce off gold-coated specimen to get these images.)

Question 9

Transmission (TEM)

Answer 9

Produces images of a specimen’s internal structure by using transmitted electrons that pass through the sample.

Question 10

Phase contrast microscopy

Answer 10

Provides increased contrast without stains (staining the cells), so the cells are still alive & can be observed living

Question 11

Brightfield microscopy

Answer 11

Objects are dark and the field is light & can be used to observe unstained living or fixed (preserved) microorganisms ; Creates a dark image against a white background.

Question 12

Brightfield microscopy (stained)

Answer 12

Staining with various dyes to enhance contrast (but the cells usually die). Most staining procedures usually requires that cells be fixed (preserved)

Question 13

Types of light microscopy

Answer 13

Bright field, phase contrast, fluorescence, & confocal fluorescence microscopy.

Question 14

Fluorescence microscopy

Answer 14

Uses specific fluorescent dyes that emits fluorescence when illuminated with ultraviolet radiation, that bind to specific molecules in a cell. (This will sometimes / most of the time kill the cell.)

Question 15

Confocal fluorescence microscopy

Answer 15

Uses a computer to put together scans at different levels of the sample ; creates sharp images of fixed (preserved) or living cells and tissues with greatly increased optical resolution and contrast

Question 16

Fluorescent molecules

Answer 16

Molecules which absorb light of one wavelength and emit (release) PART of it back out at a different / longer wavelength of light.

Question 17

Cell fractionation

Answer 17

Separation of sub-cellular components / isolation of organelles from other cellular components.

Question 18

Homogenization

Answer 18

Break open the cells, which releases the cellular components (organelles) into the solution, which then produces homogenate ; Making two mutually non-soluble liquids uniform (the same)

Question 19

Homogenate

Answer 19

A mixture of all of the components of the cell, but no intact cells.

Question 20

Centrifugation

Answer 20

Separates components (molecules) having different densities by spinning them in solution around an axis at high speed.
(The largest particles / densities centrifuge down the fastest & are the easiest).

Question 21

What happens after centrifugation?

Answer 21

A pellet(s) & a supernatant are formed

Question 22

Cell fractionation technique

Answer 22

Mixture (from fractionation) –> Homogenization –> Homogenate –> Centrifugation

Question 23

Pellet

Answer 23

Heavy organelles that sink to the bottom of the centrifugation tube, (because of size / density).

Question 24

Supernatant

Answer 24

Anything that was not large enough to be pelleted, and is still soluble in the solution ; Clear liquid remaining after sediment settles