4.1 practical experiment, fats, protein, starch and reducing sugars

 Practical task 4.1 looks at the 4 tests for identifying starch, sugars, protein and lipids.

Here you can find some of my videos of the experiment for marine science:

Starch:

For starch, we use the iodine test

the iodine solution is normally brown, but when in contact with starch it turns black within seconds.

Take the sample you want to test, put it on a plate, drop a few drops of iodine solution and note the  colour change

Sugars:

For sugars we use the Benedicts solution and a warm water bath. The benedicts solution changes colour from a clear blue to green, yellow and the red depending on the amount of reducing sugars

You take the food you want to test, cut it into smaller pieces, place it in a test tube with a few ml. of water and a few ml of Benedicts solution.

Then it's heated in a water bath with a temperature of at least 70 degrees for about 5 minutes. Colour change is then noted.

Protein:

For protein we use the Biuret test

The food to be tested is cut into as small fragments as possible, add a few ml of destilled water and then the same amount of Biuret solution.Be aware that this is a corrosive chemical, and proper lab technique and safety is important.

After a few minutes, note the colour change. A clear blue means little or no protein, a purple colour indicates the presence of protein.

Fat test:

The chosen food is grinded into small pieces and mixed with pure ethanol and allow it some time to dissolve the fat.

A test tube is filled halfway with destilled water. Then the alcohol(not the mixed foodstuff) is carefully transfered to the test tube. If there is a white layer at the top , this indicates the presence of lipids

This part of the syllabus is almost the same as experimental skill 4.1 in IGCSE Biology. So, if you have taken biology, you will notice its the same tests and skills beeing used.

the last video is for my IGCSE Biology class, but the experiment is basicly the same