Chapter 3 - Biological Molecules

Question 1

What are the different types of carbohydrates?

Answer 1

Monosaccharides (single sugars), Disaccharides (double sugars), and Polysaccharides (complex carbohydrates)

Question 2

What are the types of monosaccharides and where are they found?

Answer 2

Glucose (found in animals and plants), fructose (found in plants), galactose (found in milk sugar of mammals)

Question 3

What are the different types of disaccharides and what are they made up of?

Answer 3

Maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose + galactose)

Question 4

What are some examples of polysaccharides?

Answer 4

Starch ( found in leaves/storage organs), glycogen (found in liver/ muscle cells), cellulose (found in plant cell walls)

Question 5

What is not a reducing sugar?

Answer 5

Sucrose (cannot test using Benedict’s test)

Question 6

What is the general formula of carbohydrates

Answer 6

CnH2nOn

Question 7

What are the functions of carbohydrates?

Answer 7

• Carbohydrates are the main source of energy (glucose for aerobic respiration)
• carbohydrates are an energy storage

Question 8

What are the functions of carbohydrates?

Answer 8

• Carbohydrates are the main source of energy (glucose for aerobic respiration)
• carbohydrates are an energy storage

Question 9

What is the test for reducing sugar and how to test?

Answer 9

Benedict’s test. Add 2cm^3 of food sample into the tube. Add 2cm^3 of Benedict’s solution to the food sample. Shake the mixture and place it in a hot water bath. If the solution remained blue, reducing sugar is absent. If the solution changed from blue to green, yellow, orange, or red, reducing sugar is present.

Question 10

Does fats have more or less oxygen compared to hydrogen?

Answer 10

Less

Question 11

Hydrolysis of fat = ?

Answer 11

1 glycerol + 3 fatty acids

Question 12

What is the purpose of fats? (Name at least 3)

Answer 12

• long term energy storage
• thermal insulation
• protects vital organs
  Forms cell - membranes
• secreted as oil on the skin to reduce water loss

Question 13

What test is used to test for fats and how does it work?

Answer 13

Emulsion test. Add 2cm^3 of ethanol with 2cm^3 of food sample. Shake the contents in the tube vigorously. If fat is present, cloudy white emulsion is formed.

Question 14

What elements make up protein?

Answer 14

Carbon, hydrogen, oxygen, nitrogen, sulfur (for some proteins)

Question 15

What is the basic unit of protein?

Answer 15

Amino acid

Question 16

What is the function of protein?

Answer 16

• Growth and repair of cells
• production of enzymes, antibodies and some hormones
• Synthesis of new muscle fibres

Question 17

What is the test for protein and the procedure?

Answer 17

Biuret test. Add 2cm^3 of NaOH to 2cm^3 of food sample into a test tube and shake it thoroughly. Add 1% copper (II) sulfate solution drop by drop. If protein is present, purple and violet solution is formed.