1. what chemical indicator is used to determine amylose (starch) hydrolysis? How
ID: 193006 • Letter: 1
Question
1.
what chemical indicator is used to determine amylose (starch) hydrolysis? How does it
reveal whether s
tarch has been digested?
2.
Amylase is a hydrolase. What does that mean (you may have to consult your text if you
don’t remember this from cell biology)? What is the basic function of hydrolases? What
specific reaction does amylase catalyze?
4.
What indicates a positive fermentation test?
5.
Does the sugar tube fermentation test reveal which specific fermentation products a
bacterium makes?
6.
What does an alkaline reaction indi
cate? Why does the medium become alkaline?
7.
Why is it necessary to label your sugar tubes as soon as you remove them from the rack?
Explanation / Answer
Answer 1
Iodine reagent is used.
Test: An inoculum frim a pure culture is streaked on a sterile plate of starch agar. The inoculated plate is incubated at 35-37 for 24 hours.
Iodine reagent is then added to flood growth.
Presence of clear halos surrounding colonies is positive for their ability to digest the starch and thus indicates presence of alpha amylase.
Answer 2
Amylase an enzyme that catalyzes the hydrolysis of starch into simpler compounds . So, amylase is categorized under hydrolase.
Hydrolases catalyze reactions that involve hydrolysis. This cases usually involves the transfer of functional groups of water.
Alpha amylase occur in animals and include pancreatic and salivary amylase, the beta amylase occur in higher plants. The pancreas and salivary gland make amylase to hydrolyze dietary starch into disaccharides and trisaccharides which are converted by other enzyme to glucose to supply the body with energy.
Answer 4
Fermentation test
If lactose is fermented to produce acid end products, the pH of the medium will drop. A pH indicator in the medium changes color to indicate acid production.
Experiment:
An inoculum from a pure culture is transferred aseptically to a sterile tube of phenol red lactose broth. The inoculated table is incubated at 35-37 for 24 hours.
A positive test consists of a color change from red to yellow indicating a pH change to acidic.
Answer 5
Fermentation of sugar is indicated by a color change to yellow. It means the end product is acid.
If this color is dark pinkish red it means the end product is alkaline or basic which is due to utilization of the peptone rather than the sugar.
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