Biology: Chapter 4

Question 1

What are the 3 elements that make up carbohydrates?

Answer 1

Carbon, Hydrogen, Oxygen

Question 2

Carbohydrate components and types

Answer 2

• starch, cellulose and sugar
• made up or carbon, hydrogen and oxygen
• 1 molecule of carbohydrate has 2(carbon + oxygen) = hydrogen

Question 3

Use of Carbohydrate

Answer 3

In animals:
- transported around body as glucose
- carried in blood plasma
- used for cellular respiration
- stored as glycogen

In plants:
- used in respiration
- transport sucrose around plant body
- stored as starch
- cellulose used to make cell wall

Question 4

Structure of Starch

Answer 4

Glucose linked together and coil into spiral shape

Question 5

Structure of Glycogen

Answer 5

Glucose link together to form glycogen

Question 6

Structure of Cellulose

Answer 6

Glucose links together in a chain to form straight line

Question 7

Features of Sugar: Monosaccharides

Answer 7

• glucose, fructose, galactose
• simple sugar
• very small
• soluble in water
• sweet
• monomers of carbohydrate

Question 8

Features of Sugar: Disaccharides

Answer 8

• sucrose (glucose + fructose), lactose (galactose + glucose), maltose (glucose + glucose)
• two simple sugars joined together
• sucrose (used in hot drinks & cereals)
• maltose (malt sugar: sweet potato, honey, barley)
• soluble in water
• sweet

Question 9

List 3 substance that are included in Carbohydrates

Answer 9

Sugar, Starch, Cellulose

Question 10

Give one importance of carbohydrates in animals

Answer 10

-Glucose, transported around the body in blood plasma
- needed for energy , cellular respiration

Question 11

Features of Sugar: Polysaccharides

Answer 11

• starch, cellulose, glycogen
• many simple sugars join together
• contains thousands of sugar molecules joined in a long chain
• insoluble, do not taste sweet

Question 12

What is the category containing fats and oils?

Answer 12

Lipids

Question 13

What are lipids made up of?

Answer 13

Carbon, Hydrogen, Oxygen

Question 14

Use of fats

Answer 14

• making cell membrane
• used as energy stores
• heat insulating layer in some animals (mammals)

Question 15

What are proteins made up of?

Answer 15

Carbon, Hydrogen, Oxygen, Nitrogen

Question 16

Features of Protein: Monomer

Answer 16

• made up of amino acids
• 20 different kinds of amino acids
• each protein made up of different amino acid linked together

Question 17

Function of Protein

Answer 17

• antibodies
• enzymes
• haemoglobin
• cell membrane
• keratin (hair and nails)

Question 18

Test for Protein

Answer 18

Name: Biuret’s solution
1. Preapre clean test tube
2. Prepare food samples by cutting into small pieces
3. Add small amount of Biuret’s solution into test tube
4. Shake the test tube to mix the food sample with the solution
5. Observe for colour change from blue to violet

Results
Positive: Biuret’s solution turns from blue to violet
Negative: Biuret’s solution remains blue

Question 19

Test for Lipids (fats & oils)

Answer 19

Name: Ethanol Emulsion Test
1. The food is cut up into small pieces
2. Add food samples to small amount of ethanol and shake it to mix them.
3. Take a clean test tube and add distilled water (same amount as ethanol)
4. Add ethanol mixed with food sample into distilled water
5. Observe for any milky or cloudy emulsion.

Results
Positive: Lipids will form small droplets and make the water cloudy (emulsion)
Negative: No changes to water and ethanol mixture, no milky emulsion

Question 20

Test for Vitamin C

Answer 20

Name: DCPIP solution
1. Prepare a clean test tube and drop 1ml of DCPIP solution in with syringe
2. FOR SOLID FOODS: grind food sample and mix with distilled water
3. Use a syringe to drop the food sample slowly until the solution becomes clear
4. Record smount of food sample that was added
(The lower the amount of food sample needed to make DCPIP solution clear, the higher the amount of vitamin C in the sample)

Results
Positive: Solution in test tube will turn clear
Negative; Solution remains purple

Question 21

Test for Starch

Answer 21

Name: Iodine solution
1. Prepare a small piece of food sample
2. Add a few drops of iodine solution on the food samples
3. Observe for change of colour from brown to blue-black

Results
Positive: Iodine solution will turn from brown to blue-black
Negative: Iodine solution will remain brown

Question 21

Test for Reducing Sugar

Answer 21

Name: Benedict’s solution
1. Prepare two boiling tubes
2. Take a small piece of food sample and grind it
3. Put the food samples into the boiling tubes
4. Add some distilled water into the boiling tube and shake
5. Add a small amount of Benedict’s solution into boiling tube and shake
6. Prepare a water bath to heat the boiling tubes.
7. Observe for colour changes in heated solution

Results
Positive: Benedict’s solution changes colour from blue to green/yellow/orange/brick-red
Negative: Benedict’s solution remains blue

Question 22

What does DNA stand for?

Answer 22

DeoxyriboNucleic Acid

Question 23

What determines the sequences of amino acid?

Answer 23

Sequence of bases on DNA

Question 24

What is DNA made up of/

Answer 24

Nucleotides

Question 25

Structure of DNA molecules

Answer 25

• 2 chains of nucleotides coiled around each other (double helix)