2.3 Biological Molecules

Question 1

What are lipids?

Answer 1

a group of biological molecules including fats and oils, made from fatty acid chains and glycerol

Question 2

What elements do lipids contain?

Answer 2

Carbon
Hydrogen
Oxygen

Question 3

How do you test for fat (lipids)?

Answer 3

1. add 2cm3 of ETHANOL to the test solution
2. add 2cm3 of distilled water
3. leave for 3 minutes and then record the colour
   –> if fat is present a milky white emulsion will form
   –> if fat is not present the solution will remain colourless

Question 4

Which chemical elements are present in carbohydrates?

Answer 4

• carbon
• oxygen
• hydrogen

CHO

Question 5

Which chemical elements are present in proteins?

Answer 5

• carbon
• oxygen
• hydrogen
• sulphur
• nitrogen
• phosphorus

CHONPS

Question 6

Which molecules are carbohydrates broken down into?

Answer 6

The polymers break down into simple sugars

Question 7

Which molecules are proteins broken down into?

Answer 7

amino acids

Question 8

Which molecules are lipids broken down into?

Answer 8

The large polymers break down into 3 fatty acids and glycerol

Question 9

How to test for glucose?

Answer 9

1. Add BENEDICT’S SOLUTION into the test tube containing the food sample
2. Heat in a water bath at 60-70 degrees for 5 minutes
3. Take test tube out and record the colour
   –> if glucose is present the solution will turn brick red
   –> if glucose is not present solution will remain blue

Question 10

How to test for starch?

Answer 10

1. Pipette the sample solution into wells or on a tile
2. add drops of IODINE SOLUTION and leave for 1 minute
3. record any colour change
   –> if starch is present the solution will turn blue-black
   –> is starch is not present the solution will remain brown

Question 11

How to test for protein?

Answer 11

1. add the sample solution into a test tube
2. add drops of BIURET SOLUTION into the test tube
3. leave for 1 minute and then record the colour
   –> is protein is present the solution will turn purple
   –> if protein is not present the solution will remain blue

Question 12

What are amino acids?

Answer 12

the monomer from which proteins are assembled from

Question 13

Glycogen

Answer 13

a carbohydrate made from glucose that acts as an energy store in animals

Question 14

enzymes

Answer 14

proteins that are biological catalysts that increase the rate of reactions by providing an alternate pathway with a lower activation energy

Question 15

Active site

Answer 15

part of the enzyme that is complementary to the shape of the substance which can change shape if the enzyme is exposed to extreme pH solutions or high temperatures
–> this would result in less enzyme-substrate complexes