Question

Some sorghum seeds were soaked in water for two days. They were then broken into small pieces and placed on the surface of agar containing starch. After two days, it was found that the agar no longer contained starch.

1. How was the test for starch in the agar carried out?
2. Explain why there was no starch in the agar after two days.
3. Why were the sorghum seeds broken into smaller pieces?
4. State the observation made when the seeds were soaked in boiling water. 

Answer 1

1. Add three drops of iodine on the agar the colour of iodine remained brown indicating absence of starch in the agar;
2. Sorghum seed contain (enzyme) amylase/ptyalin (acc diastase); which converted/digested/hydrolysed/break down starch in the agar to maltose;
3. To increase surface area for working/activity/action of enzyme;
4. Brown iodine solution changes colour to blue-black since starch is not digested because the enzyme is denatured by boiling/high temperatures;