1-2 Carbohydrates

Question 1

What are carbohydrates?

Answer 1

• Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen and they are long chains of sugar units called saccharides.

Question 2

What are monosaccharides?

Answer 2

• Single monomer
• Glucose, Galactose, Fructose

Question 3

What are disaccharides?

Answer 3

• Two monosaccharides
• Maltose, two glucoses
• Sucrose, glucose and fructose
• Lactose, glucose and galactose

Question 4

What are polysaccharides?

Answer 4

• Many monosaccharides
• Glycogen and starch both formed by condensation of alpha glucose
• Cellulose formed by condensation of beta glucose.

Question 5

Describe the structure of Glycogen?

Answer 5

• Glycogen, main energy store in animals and made from glucose joined by 1,4 and 1,6 glycosidic bonds, has a large number of side branches, large but compact

Question 6

Describe the structure of Starch?

Answer 6

• Starch, main energy store in plants and is a mixture of two polysaccharides called amylose and amylopectin.
• Amylose, unbranched chain, joined by 1,4 glycosidic bonds, as a result amylose is coiled and compact so storing lots of energy.
• Amylopectin, branched, 1,4 and 1,6 glycosidic bonds. Side branches so fast energy release.

Question 7

What properties of starch make it suitable as a storage molecule?

Answer 7

• Insoluble, so will not affect cell water potential
• Compact, so a lot of energy can be stored in a small space
• Hydrolysed to release alpha glucose which can be transported easily.

Question 8

Describe the structure of cellulose?

Answer 8

• Long unbranched chains of beta glucose
• Microfibrils, strong threads which are made of parallel cellulose chains joined by hydrogen bonds forming cross linkages.

Question 9

What properties of cellulose make it suitable as a cell wall?

Answer 9

• Exerts inwards pressure and stops influx of water.
• Helps keep cell turgid, maximising surface area of plants for photosynthesis.