Chapter 4: Biological molecules

Question 1

What are the main three nutrients required by organisms?

Answer 1

Carbohydrates
Proteins
Lipids

Question 2

What are nutrients?

Answer 2

Organic molecules.

Question 3

What do you mean by organic molecules?

Answer 3

Organic molecules are those that contain carbon atoms covalently bonded to other atoms in their respective molecules

Question 4

What atoms do carbohydrates contain?

Answer 4

Carbon
Hydrogen
Oxygen

Question 5

What atoms do lipids contain?

Answer 5

Carbon
Hydrogen
Oxygen

Question 6

What atoms do proteins contain?

Answer 6

Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur (sometimes)

Question 7

Give some examples of carbohydrates.

Answer 7

Starch
Cellulose
Glycogen

Question 8

Give some examples of proteins

Answer 8

Lipase
Pepsin
Amylase
Haemoglobin
Insulin

Question 9

Give some examples of lipids.

Answer 9

Cholesterol
Triglycerides

Question 10

Write the chemical formula of glucose.

Answer 10

C6H12O6

Question 11

What is a monomer?

Answer 11

Sugars made up of one carbon ring

Question 12

What is a disaccharide?

Answer 12

A disaccharide are sugars with two carbon rings in their molecules.

Question 13

What is a polysaccharide?

Answer 13

When many starch, glycogen or cellulose molecules are joined together, the carbohydrate is called a polysaccharide

Question 14

What are proteins made up of?

Answer 14

amino acids

Question 15

How are proteins formed?

Answer 15

Each type of protein has its amino acids arranged in a particular sequence.

Even a small difference in the order of the amino acids results in a different protein being formed

Question 16

What are lipids made up of?

Answer 16

fatty acids and glycerol

Question 17

How do you test for starch?

Answer 17

Reagent: Iodine
Positive result: Brown to Blue-black colour appears

Question 18

Give some examples of food containing starch.

Answer 18

Potato
Rice
Pasta
Bread

Question 19

How do you test for reducing sugars?

Answer 19

Reagant: Benedict’s
Positive result: Blue to Yellow/Green/Orange/Brick red

Question 20

Give some examples of foods with reducing sugars

Answer 20

Glucose (table sugar)
Fructose (fruits)
Maltose

Question 21

How do you test for proteins?

Answer 21

Reagent: Biuret
Positive result: Turns purple/lilac

Question 22

Give some examples of foods with proteins.

Answer 22

Milk
Eggs
Cheese

Question 23

How do you test for fats and oils?

Answer 23

Test: Ethanol emulsion test (a sample with ethanol is poured into distilled water)
Positive result: A milky white emulsion forms

Question 24

Give some examples of foods with fats

Answer 24

Cooking oil
Butter

Question 25

How do you test for Vitamin C?

Answer 25

Reagent: DCPIP
Positive result: Blue to purple/pink then Pink to clear

Question 26

Give examples of foods containing Vitamin C.

Answer 26

Citrus fruit
Fruit juices

Question 27

State the bases of DNA.

Answer 27

Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

A pairs with T
C pairs with G

Question 28

Describe the structure of DNA.

Answer 28

A DNA molecule is made up of long chains of nucleotides, forming two strands.

A nucleotide is a 5-carbon sugar molecule joined to a phosphate group and an organic base.