Testing For Biological Molecules

Question 1

What’s something we do at the start of each testing?

Answer 1

Grind the food we are testing we a small amount of distilled water.

Question 2

What do we grind food in?

Answer 2

A mortar and pestle.

Question 3

What do we do once the grinder mixture is a paste?

Answer 3

Add more distilled water and stir.

Question 4

What do we do after we mix the food paste and distilled water?

Answer 4

We filter the mixture to remove solid food particles.

Question 5

Why do we filter solid food particles?

Answer 5

As they could make the test results difficult to see.

Question 6

What is the filtrate?

Answer 6

The food solution that passes through the filter.

Question 7

How much of the food solutions do we place in the test tube?

Answer 7

3cm^3

Question 8

What solution do we add to test for starch?

Answer 8

A solution containing iodine and potassium iodide.

Question 9

How much iodine solution do we add to test for starch?

Answer 9

1cm^3

Question 10

What colour does the solution turn if starch is present?

Answer 10

A blue-black colour.

Question 11

What colour would the solution be if starch isn’t present?

Answer 11

Remain orange.

Question 12

What solution is first added to test for proteins?

Answer 12

Dilute sodium hydroxide solution.

Question 13

What solution is added second to test for proteins?

Answer 13

Dilute copper (||) sulfate solution.

Question 14

What do we do after we add in solutions?

Answer 14

Mix.

Question 15

What colour does the solution turn if protein is present?

Answer 15

Purple or lilac.

Question 16

What colour will the solution be if protein isn’t present?

Answer 16

Remain blue.

Question 17

What is biuret solution?

Answer 17

A premixed solution of sodium hydroxide and copper (||) sulfate.

Question 18

What does the test for protein actually detect?

Answer 18

Peptide bonds.

Question 19

What are peptide bonds found in?

Answer 19

Proteins.

Question 20

What are peptide bonds not in?

Answer 20

Amino acids.

Question 21

In what test must the food solution not be filtered?

Answer 21

Test for lipids.

Question 22

Why is the lipid solution not filtered?

Answer 22

As the lipids stick to the filter paper.

Question 23

What do we do to the lipid food solution instead of filtering it?

Answer 23

Leave it to allow the food particles to settle.

Question 24

What and how much do we add to test for lipids?

Answer 24

3cm^3 of ethanol and 3cm^3 of water.

Question 25

What do we do after we add the ethanol and water to the lipid solution?

Answer 25

Shake it.

Question 26

What will happen if lipids are present?

Answer 26

A white cloudy emulsion will form.

Question 27

How do we know lipids aren’t present?

Answer 27

If the solution stays clear.

Question 28

Why must the lipid experiment not be carried out near flames?

Answer 28

As ethanol is highly flammable.