Digestive Systems and Enzymes - Food Molecules and Tests

Question 1

how do you prepare a food sample

Answer 1

1) get a piece of food and break it up using a pestle and mortar
2) Transfer the ground up food to a beaker and add some distilled water
3) Give the mixture a good stir with a glass rod
4) Filter the solution using a funnel lined with filter paper

Question 2

what do you use to test for sugars and how do you do it

Answer 2

for reducing sugars you use the benedict’s test

1) Prepare a food sample and transfer 5cm^3 to a test tube
2) prepare a 75 celcius water bath
3) add 10 drops benedict solution to the test tube
4) place and leave the test tube in the water bath for 5 minutes
5) if the food sample contains a reducing sugar, the solution will turn from blue to green/yellow/brick-red

Question 3

What do you use to test for starch and how do you do it

Answer 3

to test for starch you use iodine solution

1) make a food sample and transfer 5cm^3 to a test tube
2) Add a few drops of iodine solution and gently shake
3) If the sample contains starch the colour of the solution will change from browny-orange to black/blue-black

Question 4

How do you test for proteins

Answer 4

for proteins you use the Biuret Test

1) prepare a sample of ur food and transfer 2cm^3 to a test tube
2) add 2cm^3 of biuret solution to the sample and gently shake
3) If the sample contains protein it will change from blue to purple

Question 5

How do you test for lipids

Answer 5

Use the Sudan III test for lipids

1) prepare a sample of the food (dont filter it) and transfer 5cm^3 to a test tube
2) add 3 drops of Sudan III stain solution and gently shake
3) If the sample contains lipids the mixture will separate into two layer, the top will be bright red