Carbohydrates

Question 1

What elements do carbohydrates consist of?

Answer 1

Carbon, Hydrogen and Oxygen

Question 2

How to identify the difference between α and β-glucose?

Answer 2

In α-glucose , the (-OH) group attached to C1 is below the plane of the ring whereas in the β-glucose, the (-OH) group attached to C1 is above the plane of the ring.

Question 3

Significance of molecular structure of monosaccharides?

Answer 3

• Small in size and has many hydroxyl groups that can form hydrogen bonds with water, making it readily soluble in water
• Linear form possesses a free carbonyl group (C=O), gives them reducing ability hence called reducing sugars
• Pentoses and hexoses can exist as rings which are stable building blocks for larger molecules
• Ring structures exhibit α- and β- isomerism, increasing diversity of monosaccharides

Question 4

What is the bond between disaccharides

Answer 4

Glycosidic bond

Question 5

State the 4 polysaccharides?

Answer 5

Glycogen, Amylose, Amylopectin and Cellulose

Question 6

What is the monomer for starch (amylose and amylopectin)?

Answer 6

α-monomers

Question 7

What is the monomer for glycogen?

Answer 7

α-monomers

Question 8

What is the monomer for cellulose

Answer 8

β-monomers

Question 9

What are the bonds found in starch?

Answer 9

α(1-4) glycosidic bonds and α(1-6) glycosidic bonds

Question 10

What are the bonds found in glycogen?

Answer 10

α(1-4) glycosidic bonds and α(1-6) glycosidic bonds

Question 11

How do the structures of glycogen, amylose and amylopectin determine its function?

Answer 11

• Made of many glucose residues, making it a large energy store that can be hydrolysed and a large molecule that is insoluble in water thus not affecting water potential of cell.
• All comprises of helices making it a compact molecule
• Intramolecular hydrogen bonding and projection of hydroxyl groups into core reduces available hydroxyl groups for hydrogen bonding with water, making it insoluble
• Amylopectin and glycogen are branched allowing mutiple enzymes to work at the same time due to multiple branch ends

Question 12

What are the bonds in cellulose?

Answer 12

β(1-4) glycosidic bond

Question 13

How does structure of cellulose contribute to its function and properties?

Answer 13

• Adjacent β-glucose monomers are rotated 180° with respect to each other, thus cellulose molecules are linear and able to form hydrogen bonds with adjacent hydroxyl groups with parallel cellulose chains, forming microfibrils which has high tensile stregnth.
• Few hydroxyl groups available for hydrogen bonding with water, thus microfibrils are insoluble in water

Question 14

Where is starch stored at?

Answer 14

Stored as granules in chloroplast

Question 15

Where is glycogen stored at?

Answer 15

Stored in liver and muscle cells