Digestion

Question 2

he material from which Visking tubing is made is partially permeable. Starch was added to visking tube with amylase

After 15 minutes, the student removed samples from the liquid in the beaker and from the liquid inside the Visking tubing. She carried out biochemical tests on these samples. She drew the table below to record her results.

(b) Complete the table by placing a tick (✔) in each box that you expect to have shown a positive result.
Biochemical test

Liquid from beaker

Liquid inside Visking tubing

Biuret reagent

Iodine in potassium iodide

Benedict’s solution

Answer 2

tick inside liquid in beaker only benedicts

tick inside visking tube all 3

  Biuret: protein molecules too large to pass through tubing;

Neutral: enzyme molecules

2. Iodine in potassium iodide solution: starch molecules too large to pass through tubing;

If no tick in 04.2, allow no starch hydrolysed

3. Benedict’s: starch hydrolysed to maltose, which is able to pass through tubing.

Reject: glucose