1) Carbohydrate fermentation tests typically use media that contain a pH indicator such as phenol red. Explain the purpose of a pH indicator and the conditions under which phenol red turns yellow and turns magenta.
2) The metabolism of four sugars were tested in this lab exercise: glucose, lactose, sucrose, and mannitol. Research these sugars and describe one characteristic of each structure that makes them unique from the others.
3) Open your two lab reports from this lab and compare them side by side. Which test results were the same? Which test results were different? Were any of the test results not helpful (did not eliminate any organisms)? If so, which one(s)?
4) Based on your answers for question numbers 3 and 4 above, and your knowledge of cell structures used for metabolism, why might organisms that can metabolize some sugars not be able to metabolize them all?
5) Is it possible to fully identify an unknown using only phenol red carbohydrate tests? Explain your answer.