Question

question 15
select all correct statements regarding this starch test results
□ the enzyme tested for is amylase
□ iodine binds with starch to give a brown color
□ organism b is able to hydrolyze iodine.
□ organism a is positive for starch test.
□ organism b is positive for starch test.
□ iodine binds with starch to give a yellow halo
□ organism a is able to hydrolyze iodine

Explanation:

1. Amylase test: The starch test here is for amylase (enzyme that breaks starch), so "The enzyme tested for is amylase" is correct.
2. Iodine - starch interaction: Iodine binds to starch to give a blue - black color, but in some visual results (like the plate here), the unhydrolyzed starch + iodine might appear brownish in the context of the plate. However, the key is about the test. Also, when an organism can hydrolyze starch (has amylase), the area around it won't show starch (so iodine won't bind there, creating a halo).
3. Organism A: The area around A has no starch (so iodine doesn't bind, dark area), meaning A hydrolyzed starch (positive for amylase, so "Organism A is positive for starch test" (since it can break starch, the test for starch presence would be negative in its halo, but the test for amylase (starch hydrolysis) is positive; maybe the wording here is about starch presence? Wait, no—if the plate has starch, and we add iodine, areas with starch turn (brown/blue - black), areas without (because organism hydrolyzed it) don't. So Organism A: the clear (dark) area around it means starch was hydrolyzed (so A has amylase). Organism B: the area around it is still brown (starch present), so B didn't hydrolyze starch.

• "The enzyme tested for is amylase": Correct, as starch test for amylase (amylase breaks starch).
• "Iodine binds with starch to give a brown color": In the context of this plate, the starch - iodine complex here appears brown (maybe due to the medium), so this can be correct.
• "Organism A is positive for starch test": If "starch test" here means starch hydrolysis (amylase presence), then A is positive (since it broke starch, so the area around it has no starch, so iodine doesn't bind there—so A is positive for amylase (starch hydrolysis), which is the test.
• Let's re - evaluate each option:
• "The enzyme tested for is amylase": Correct (starch test is for amylase, which digests starch).
• "Iodine binds with starch to give a brown color": In the image, the starch - containing areas are brown, so this is correct (maybe the iodine - starch complex here is brown, not blue - black, due to the medium).
• "Organism A is positive for starch test": If the test is for starch hydrolysis (amylase), then A is positive (since it hydrolyzed starch, so the area around it has no starch—so the test for amylase (starch breakdown) is positive).
• Other options:
• "Organism B is able to hydrolyze iodine": No, organisms don't hydrolyze iodine; they hydrolyze starch.
• "Organism B is positive for starch test": B's area has starch (brown), so if the test is for starch presence, B is positive (but the test is for amylase, so B can't break starch, so starch is present—so this could be correct if "starch test" is for starch presence. Wait, the question is "regarding this starch test results". The starch test here: the plate has starch, iodine is added. Areas with starch (iodine binds) are brown, areas without (starch hydrolyzed) are not. So:
• Organism A: area around it has no starch (so iodine doesn't bind, dark), so A hydrolyzed starch (positive for amylase, so "Organism A is positive for starch test" (if test is for amylase - mediated starch breakdown)).
• Organism B: area around it has starch (brown), so B didn't hydrolyze starch (negative for amylase, positive for starch presence).
• "Iodine binds with starch to give a brown color": Correct (as per the plate's appearance).
• "The enzyme tested for is amylase": Correct.

Answer:

• The enzyme tested for is amylase
• Iodine binds with starch to give a brown color
• Organism A is positive for starch test
• Organism B is positive for starch test

(Note: The exact correctness might depend on the precise interpretation of "starch test"—whether it's for starch presence or starch hydrolysis. But based on typical starch hydrolysis test (amylase test) and the plate's appearance, these options fit.)