Starch And Casein Hydrolysis Flashcards
Hydrolysis or hydrolytic reactions
Reactions that use water to split complex molecules
Enzymes needed for hydrolysis or hydrolytic reactions
Hydrolytic enzymes
Intracellular versus extracellular in a hydrolysis reaction
Intracellular happens when When an enzyme catalyzes its reaction inside the cell
Extracellular happens when enzymes are secreted from the organism to catalyze reactions outside the cell
What are exoenzymes
Another name for extracellular enzymes
Starch agar
Dnase agar
Tributyrin agar
Milk agar that identify enzymes with which type of characteristics
Extracellular enzymes capable of diffusing into the medium and producing a distinguishable Halo of clearing around the bacterial growth
What does nutrient gelatin detect in the starch hydrolysis test
Gelatin Ace an exoenzyme that liquefies the solid medium
What type of enzymes are detected by the urease and bile esculin tests
Hydrolytic enzymes that are intracellular and produce identifiable color changes in the medium
What does the pyr test identify
A specific aminopeptidase that removes amino acid at the end of a polypeptide
What is starch?
A complex polysaccharide compound composed of a glucose polymers in one of two forms
Linear amylose and branched amylopectin usually as a mixture with branched being predominant
How is amylopectin different than amylose?
Amlopectin contains side chains covalently bonded to approximately every 30th glucose in the main chain
How is starch? Digested by bacteria
It is too large to pass through the bacterial cell membrane. Therefore, it must be digested extracellularly or in the periplasmic space in the case of gram-negative bacteria into smaller molecules
What bacteria are used for the starch hydrolysis test?
Bacillus subtilis
E. Coli
How do you inoculate for the starch hydrolysis test?
Divide the plate in half with a marker. spot Inoculate two sectors with the different organisms near the edge of the plate
How do you incubate for the starch hydrolysis test
35° plus or minus 2° C for 24 hours
After incubation, how do you check the results of the starch hydrolysis test
Use a marking pen to indicate the margins of growth for each bacteria
Cover the growth and surrounding areas with gram iodine and allow to soak in
A halo around the growth constitutes a positive result
A positive result in the starch hydrolysis test means what is present
Amylase is present
How do many bacteria use proteins
They use them as a source of amino acids for synthesis of their own proteins and other compounds and as an energy source
How do some bacteria use hydrolysis on proteins as in the casein hydrolysis test?
They produce and secrete enzymes into the environment that catalyze the hydrolysis of large proteins into smaller peptides or individual amino acids therefore enabling their uptake across the membrane
What is casease
A specific proteolytic enzyme That some bacteria produce to hydrolyze the milk protein casein
What does the milk protein casein do to milk
It gives it it’s white color but when broken down into smaller fragments it loses its opacity and becomes clear
What is milk? Agar
An undefined medium containing pancreatic digestive casein
Yeast extract
Dextrose
And powdered milk
What does a positive result look like in a casein hydrolysis test?
There will be a clearing in the milk. Agar around the bacteria
This proves that the enzyme casease is present
How do you inoculate the milk agar plate in the casein hydrolysis test?
Divide the plate into equal sectors
Spot inoculate with test organisms on each edge of the plate
How long to incubate for the casein hydrolysis test
- Plus or minus 2° C for 24 hours
