Amylase is a biological polymer. Name the monomer (smaller molecule) that forms this polymer.

Name two organs in the human digestive system that produce amylase.

Explain how amylase breaks down starch. Answer in terms of the 'lock and key theory'.

A student investigated the effect of temperature on the activity of amylase.

The student used the following method:

1. Measure $5{cm}^3$ of starch suspension and $2{cm}^3$ of a pH 7 buffer solution into a test tube.
2. Place this test tube and a separate tube containing $2{cm}^3$ of amylase solution into a water bath at $40^{\circ }C$ for 5 minutes.
3. Add the amylase solution to the starch mixture, stir, and start a stopwatch.
4. Every 30 seconds, use a pipette to add one drop of the mixture to a drop of iodine solution in a well on a spotting tile. Iodine is normally yellow-brown, but turns blue-black in the presence of starch.
5. Record the time taken for the iodine solution to remain yellow-brown.
6. Repeat the experiment using water baths maintained at different temperatures.

Why did the student leave the tubes in the water bath for 5 minutes before mixing them?

Name two control variables the student kept constant in this investigation.

Explain why the iodine solution remains yellow-brown after a certain time has passed.