7.1 Visualizing cells

Question 1

What are 4 characteristic ways that light or electrons can interact with matter?

Answer 1

Absorption, Refraction, Reflection, Fluorescence

Question 2

Why does an electron microscope see more detail than a light microscope?

Answer 2

Uses electrons to resolve fine structure of the cell

Question 3

What 2 methods is used to visualize light that is defracted by a specimen?

Answer 3

Light microscopy and darkfield imaging

Question 4

Fluorescent molecules absorb ____ light and emit _____ and longer wavelength light.

Answer 4

high energy light/less energetic light

Question 5

Fluorescent dye absorb wavelengths between ____ and ____ nm and emit orange, yellow or greenish light

Answer 5

230/350nm

Question 6

Fluorescent microscopes

Answer 6

• visualize specimens tagged with fluorescent dye.
• source of illumination is UV light.
• Primarily used to detect antigen-antibody reactions

Question 7

Phase contrast microscope

Answer 7

Observation of unstained microorganisms is possible with this microscope….light is transmitted thro a specimen with a refractive index different from that of the surrounding medium. A portion of the light is refracted (bent) due to slight variations in density and thickness of the cellular components.
The images appear dark against a light background

Question 8

GFP fusion proteins

Answer 8

ADVANTAGES:
Expressed fusion proteins are generally not toxic to cells. Detection does not require fixation or permeability of cells so the likelihood of artifacts is reduced
DISADVANTAGES:
large GFP-tag affects the function of the fused protein of interest, GFP cannot be amplified in a controlled manner