B3 - organisation and the digestive system

Question 1

How do you test for protein?

Answer 1

1. Place a small amount of food in a test tube.
2. Add 1 cm3 of Biuret reagent. Alternatively add 1 cm
   sodium hydroxide solution and then add a few drops of
   copper sulfate solution.
3. Blue Biuret reagent turns purple if a protein is present.
4. Record your result in the results table.
5. Repeat steps 1–4 for other types of food

Question 2

How do you test for starch?

Answer 2

1. Place a small amount of food on the spotting tile.
2. Add a few drops of iodine solution to the food on the
   spotting tile.
3. Yellow–red iodine solution turns blue–black if starch is
   present.
4. Record your result in the results table.
5. Repeat steps 1–4 for other types of food.

Question 3

How do you test for sugar?

Answer 3

1 Place a small amount of food in a test tube.
2 Add enough Benedict’s solution to cover the food.
3 Place the test tube in a warm water bath for 10 minutes.
4 Blue Benedict’s solution turns brick red on heating if a
sugar such as glucose is present.
5 Record your result in the results table.
6. Repeat steps 1–5 for other types of food.

Question 4

How do you test for lipids (fats)

Answer 4

1 Place a small amount of food into a test tube.
2 Add a few drops of ethanol to the test tube.
3 Shake the test tube and leave for 1 minute.
4 Pour the solution into a test tube of water.
5 Ethanol added to a solution gives a cloudy white layer if
a lipid is present.
6 Record your result in the results table.
7 Repeat steps 1–6 for other types of food.

Question 5

What is starch made of?

Answer 5

Simple sugars

Question 6

What do the fatty tails determine about lipids?

Answer 6

How saturated they are

Question 7

What enzyme breaks down protein?

Answer 7

Protease

Question 8

What enzyme breaks down carbohydrates?

Answer 8

Carbohydrase

Question 9

What enzyme breaks down lipids?

Answer 9

Lipase

Question 10

Where, in the digestive system, does protease work?

Answer 10

In the stomach and small intestine (produced in the pancreas)

Question 11

Where, in the digestive system, does lipase work?

Answer 11

Small intestine (produced in the pancreas)

• The process is helped by bile - Bile increases surface area of fats, which makes it easier for enzymes to break the fats down

Question 12

Where, in the digestive system, does carbohydrase work?

Answer 12

In the mouth. More specifically, in the salivate glands

Question 13

What is a specific example of a protease enzyme?

Answer 13

Pepsin

Question 14

What is a specific example of a carbohydrase enzyme?

Answer 14

Amylase