Lab Exam 1

Question 1

Homogenization

Answer 1

Cell walls of the bacteria are broken down

Question 2

Purpose of EDTA

Answer 2

Disrupts the cell membrane

Question 3

Purpose of proteinase K

Answer 3

Degrades the proteins

Question 4

Purpose of phenol/chloroform

Answer 4

Denatures proteins and separates them from the DNA

Question 5

Precipitation

Answer 5

DNA is concentrated by removing it from the aqueous layer

Question 6

Purpose of sodium acetate

Answer 6

Neutralizes the charge of the sugar-phosphate backbone making the DNA less hydrophilic

Question 7

Deproteinization

Answer 7

Proteins in the cells are removed

Question 8

Non-fastidious bacteria

Answer 8

Do not require additional nutrients for growth

Question 9

Fastidious bacteria

Answer 9

Requires CHNOPS and additional nutrients for growth

Question 10

Defined media

Answer 10

Exact chemical composition is known
Growth of non-fastidious bacteria

Question 11

Complex media

Answer 11

Contains sources for CHNOPS but exact composition not known

Question 12

Enriched media

Answer 12

Contains sources of CHNOPS plus additional nutrients
Ex) Blood Agar

Question 13

Differential media

Answer 13

Appearance of bacteria depends on their ability to us a specific substrate or produces a specific enzyme
Ex) Blood agar

Question 14

Basic dyes

Answer 14

Have a positive charge and stain the microbial cells

Question 15

Acidic dyes

Answer 15

Have a negative charge and stain the background

Question 16

Gram positive cells stain what color?

Answer 16

Blue/violet

Question 17

Gram negative cells stain what color?

Answer 17

Pink

Question 18

Crystal violet dye

Answer 18

Basic dye; stains all bacteria blue/violet

Question 19

Gram’s Iodine

Answer 19

Forms a complex with the crystal violet w/in the peptidoglycan of gram positive cell walls

Question 20

Ethanol Stain

Answer 20

Decolorizer; solubilizes the outer membrane of gram negative cells and removes the crystal violet. Gram positive cells resist decolorization.