Excercise 5-3 Micro Lab: Phenol Red Broth

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1

Phenol Red Broth

a differential medium. with phenol and peptone, prepared as a base to which a carbohydrate is added

2

Phenol red is _____ below 6.8 pH, ________ above 7.4, and ______ inbetween

yellow, pink to magenta, red

3

What causes the phenol red indicator to turn yellow?

acid production from fermentation of the carbohydrate lowers the pH

4

What causes the phenol red indicator to turn pink?

deamination of peptone amino acids produces ammonia NH3 which raises the pH

5

Why is PR broth used?

to differentiate members of Enterobacteriaceae and to distinguish them from other Gram negative rods

6

carbohydrate fermentation

the metabolic process by which an organic molecule acts as an electron donor (becoming oxidized in the process) and one or more of its organic products act as the final electron acceptor (FEA).

hydrolysis of disaccharides prior to the fermentation reaction

7

lactose and sucrose fermenter

an organism that splits the disaccharide lactose/sucrose into the monosaccharides glucose and galactose and then ferments the monosaccharides

8

fermenter

this term should be assumed to include the initial hydrolysis and/or conversion reactions

9

fermentation of glucose always begins with the production of ________ and does so through the process of _______

pyruvate

glycolysis

10

4 end products of pyruvate fermentation

1. organic acids
2. alcohols
3. hydrogen
4. carbon dioxide gas