~Q. Take 1 ml starch solution (1%) in two test tubes A and B. Add 1 ml of saliva to test tube a and leave both the test tubes undisturbed for 15 min. Now, add a few drops of iodine solution to the test tubes.
a) In which of the test tube, do you observe a colour change?
b) What does this indicate about the presence or absence of starch in both the test tubes?
c) Conclude about the action of saliva on starch.
a) Colour change will be observed in test tube B where saliva is not added.
b) Iodine changes the colour of starch. If starch is present then blue black colour is formed.
c) Saliva consists of salivary amylase which acts on the starch and convert it into glucose. Glucose does not give colour with iodine. Hence, no colour appears in test tube A where saliva is present.
b) Iodine changes the colour of starch. If starch is present then blue black colour is formed.
c) Saliva consists of salivary amylase which acts on the starch and convert it into glucose. Glucose does not give colour with iodine. Hence, no colour appears in test tube A where saliva is present.