Chapter 4 - Biological Molecules

Question 1

Why are biological molecules important in organism?

Answer 1

They are needed to build structure and for use in metabolic reactions

Question 2

What are carbohydrates made up of?

Answer 2

Carbohydrates are made up of sugar molecules containing carbon, hydrogen and oxygen atoms.

Question 3

When glucose molecules bind together in a chain what can be made?

Answer 3

cellulose, starch and glycogen

Question 4

What are monosaccharides? Name an example and some characteristics of them.

Answer 4

Monosaccharides are simple sugars such as glucose and taste sweet and are very small

Question 5

What is the symbol formula of glucose?

Answer 5

C6H12O6

Question 6

What are polysaccharides? Name an example and some characteristics of them

Answer 6

A chain of many simple sugars such as starch and are mostly insoluble and don’t taste sweet

Question 7

In what form are excess sugars stored in plants?

Answer 7

Sugars are stored as starch usually in the tissue and seeds.

Question 8

In what form are excess sugars stored in animals?

Answer 8

Sugars are stored as glycogen in the liver

Question 9

Functions of carbohydrates:

Answer 9

• Needed for energy released by respiration
• Stored as glycogen in animals in liver
• Stored as starch in plants seeds or tubers
• Used to make cellulose, very strong

Question 10

What are fats also known as? and what are they made up of?

Answer 10

Fats are also known as lipids and oils and are made up of glycerol and fatty acids

Question 11

What do fats contain?

Answer 11

Fats contain carbon, hydrogen and oxygen

Question 12

Functions of fats:

Answer 12

• Can be used to release energy
• Extra energy from fat makes it useful for storing energy
• Insulates body heat
• Plants store it in oils

Question 13

What do proteins contain?

Answer 13

Nitrogen, carbon, hydrogen, oxygen and sulphur. They make up amino acids which bind in a chain and different arrangements make different proteins and shapes.

Question 14

Functions of proteins:

Answer 14

• Your hair and nails are made up of a protein called keratin
• Proteins in food used for making new cells
• Cell membranes and cytoplasm contain alot of protein
• Needed for antibodies
• For enzymes

Question 15

What does DNA stand for?

Answer 15

Deoxyribonucleic acid

Question 16

What is the structure of DNA?

Answer 16

It is composed of two strands coiled around each other to form a double helix. Each strand made of a sugar backbone with bases attached. These bases bind to bases on the other strand to form cross links

Question 17

Which bases bind to each other?

Answer 17

C-G and A-T

Question 18

Why is water important?

Answer 18

• It acts as a solvent in which chemical reactions occur
• Helps to maintain a constant temperature
• Needed for digestion as a medium for enzymes and to allow free passage of digestive product
• Allows soluble molecules in digestion to be transported around and through cell membranes
• Transports waste products such as urea

Question 19

Chemical test for starch and the method:

Answer 19

Iodine test, add iodine solution to sample a colour change from yellow-brown to blue - black indicates presence of starch

Question 20

Chemical test for reducing sugars and method:

Answer 20

Benedicts test, add sample to benedicts solution and heat to 80 C. Colour change from blue to brick red indicates presence of glucose and other reducing sugars

Question 21

Chemical test for proteins and method:

Answer 21

Biuret test, sample solution added to tube with equal amount of sodium/potassium hydroxide and add a few drops of copper sulphate solution. Colour change from blue to purple

Question 22

Chemical test for fats and oils and method:

Answer 22

Emulsion test, add sample to tube and add ethanol, Shake tube and then add water and shake gently. Colour change from clear to cloudy white

Question 23

Chemical test for Vitamin C and method:

Answer 23

DCPIP test, add DPIP to tube then sample and shake gently, colour change from blue to colourless.