Polysaccharide

Question 1

What are polysaccharides formed from?

Answer 1

Joining of glucose molecules during condensation reactions

The main polysaccharides include cellulose, starch, and glycogen.

Question 2

Glycogen and starch are formed by the condensation of _______.

Answer 2

a-glucose

Cellulose is formed by the condensation of B-glucose.

Question 3

What are the characteristics of polysaccharides?

Answer 3

• Do not taste sweet
• Relatively insoluble in water
• Non-reducing

They give a negative result in the Benedict’s test and function as storage or structural molecules.

Question 4

What is the primary function of starch in plants?

Answer 4

Storage carbohydrate

Starch consists of long, branched chains of a-glucose molecules linked by glycosidic bonds.

Question 5

Where is starch stored in plant cells?

Answer 5

In starch grains in the cytoplasm

Starch is ideally suited for storage due to its size and insolubility.

Question 6

List the reasons why starch is suited for its function as a storage compound.

Answer 6

• Large, cannot cross cell-surface membrane
• Insoluble, osmotically inactive
• Helical shape, compact store
• Branched, easy glucose release

These features prevent cell damage and facilitate respiration.

Question 7

How can starch be detected in a sample?

Answer 7

Using the iodine test

Add 2-3 drops of iodine/potassium iodide solution; a blue/black color indicates starch presence.

Question 8

What color indicates the presence of starch in the iodine test?

Answer 8

Blue / black

If no starch is present, the iodine solution remains orange / yellow.

Question 9

What is glycogen?

Answer 9

The storage carbohydrate found in the cytoplasm of animal cells

Glycogen is formed by the condensation of a-glucose and is stored in large amounts in liver and muscle tissues.

Question 10

List two reasons why glycogen is ideally suited to its function as a storage compound.

Answer 10

• It is insoluble and osmotically inactive
• It can be hydrolysed rapidly to release glucose for respiration

These properties prevent cell damage and allow for quick energy release.

Question 11

What is the primary structural difference between glycogen and starch?

Answer 11

Glycogen has more branches (free ends) than starch

This branching allows for faster hydrolysis of glycogen.

Question 12

What is cellulose and where is it found?

Answer 12

Found in the cell wall of plants

Cellulose provides rigidity and shape to the cell, preventing bursting (osmolysis).

Question 13

Cellulose is a polymer of _______ molecules joined by glycosidic bonds.

Answer 13

B-glucose

These bonds are formed in condensation reactions to produce long, straight chains.

Question 14

In cellulose, how are the B-glucose monomers arranged?

Answer 14

Every other B-glucose monomer is inverted

This arrangement differs from the condensation of a-glucose monomers in starch.

Question 15

What structural feature of cellulose contributes to its strength?

Answer 15

Hydrogen bonds between hydroxyl (OH) groups of adjacent chains

These bonds form a three-dimensional structure known as a microfibril.

Question 16

What is the structure of cellulose?

Answer 16

Long straight polymer of B-glucose monomers

Cellulose is a key structural component in plant cell walls.

Question 17

What type of bonds do OH groups form with other B-glucose polymers?

Answer 17

Hydrogen bonds

These bonds are weak individually but collectively provide significant strength.

Question 18

True or false: Hydrogen bonds in cellulose are strong.

Answer 18

FALSE

Hydrogen bonds are weak, but their large number contributes to the overall strength of cellulose.

Question 19

What is a microfibril in the context of cellulose?

Answer 19

Part of a microfibril

Microfibrils are composed of cellulose molecules and are crucial for the structural integrity of plant cell walls.

Question 20

What are the components of a cell wall in plants?

Answer 20

• Cellulose microfibrils
• B-glucose polymers

These components work together to provide strength and rigidity to plant cells.