Carbohydrates

Question 1

Properties of monosaccharides (Physical & Chemical) + reasons

Answer 1

Physical:
Soluble in water due to its small size and presence of numerous polar (-OH) groups that can form hydrogen bonds with water.

Chemical:
Are reducing sugars due to the presence of a (C=O) group that can donate electrons to reduce Cu2+ to Cu+ in Benedict’s test.

Question 2

What is a glycosidic covalent bond? How is it formed?

Answer 2

It is a covalent bond that links 2 monosaccharides in a disaccharide.

Formed via a condensation reaction between 2 monosaccharides, involving the loss of 1 water molecule.

Question 3

How is a glycosidic bond broken?

Answer 3

Hydrolysis- Breaking the glycosidic covalent bond with the addition of 1 water molecule.

2 ways:
Enzymatic
Acid Hydrolysis: Sugar is incubated with an acid at high temperature to facilitate the cleavage of the bond.

Question 4

Properties of disaccharides (Physical + Chemical)

Answer 4

Physical:
Same as monosaccharides

Chemical:
Able to undergo hydrolysis to form 2 monosaccharides
Are reducing sugars except sucrose

Question 5

Types of polysaccharides? + Examples

Answer 5

Energy storage
Starch / Glycogen

Structural
Cellulose

Question 6

What is the function of starch?

Answer 6

It serves as an energy storage molecule in plants. It is stored as starch granules within cellular structures such as chloroplasts.

Question 7

What is the structure and properties of starch?

Answer 7

Structure:
Polymer of α-glucose monomers, and consists of 2 types of polymers: Amylose and amylopectin.

Properties:
Insoluble in water due to its large size.

Question 8

Details about amylose (3 points)

Answer 8

It consists of α-glucose monomers joined by α-1,4 glycosidic bonds.

This gives rise to a compact helix: Many glucose molecules can be stored in the limited space of the plant cell.

(-OH) Groups on carbon 2 of each chain projects into the helix > Forms hydrogen bonds with each other > Stabilizes the helical shape.

Question 9

Details about amylopectin (2 points)

Answer 9

It consists of α-glucose monomers joined by α-1,4 glycosidic bonds and α-1,6 glycosidic bonds at branch points.

Branching provides many ends which are accessible to hydrolytic enzymes, allowing for the quick* hydrolysis of amylopectin to release many glucose molecules.

Question 10

Details about glycogen

Answer 10

It consists of α-glucose monomers joined by:

α-1,4 glycosidic bonds
Gives rise to helical structure of glycogen > compact > Able to store more glucose molecules within the limited space of the storage cell

α-1,6 glycosidic bonds at branch points
Branching provides many ends which are accessible to hydrolytic enzymes, allowing for the quick* hydrolysis of glycogen to release many glucose molecules.