Topic 8 - Carbohydrates

Question 1

Carbohydrate

Answer 1

Biological macromolecule (polymer) in which the ratio of carbon to hydrogen to oxygen is 1:2:1
- Molecular formula (CH2O)n, where n represents number of carbons

Question 2

What is the function of carbohydrates?

Answer 2

• Serve as energy source and structural support in cells; form arthropods’ cellular exoskeleton

Question 3

What is the monomer of carbohydrates?

Answer 3

Monosaccharides
- Aldose: R-CHO (aldehyde group)
- Ketose: RC(=O)R’ (ketone group)
- Triose: 3 carbons
- Pentose: 5 carbons (ex. ribose)
- Hexose: 6 carbons (ex. glucose)

Question 4

True or false: monosaccharides can exist as a linear chains or as ring-shaped molecules

Answer 4

True

Question 5

Name some common monosaccharides.

Answer 5

Glucose, fructose, ribose, deoxyribose

Question 6

Name the 2 different forms of glucose in a ring structure.

Answer 6

• α-glucose - hydroxyl (OH) group is below carbon 1; 1,4 OH have the same orientation
• β-glucose - hydroxyl (OH) group is above carbon 1; 1,4 OH have the opposite orientation

Question 7

Disaccharides

Answer 7

Two monomers linked by a glycosidic bond

Question 8

Glycosidic bond

Answer 8

A type of covalent bond between two monosaccharides; formed by dehydration synthesis

Question 9

Name some common disaccharides.

Answer 9

Lactose, maltose, and sucrose

Question 10

Polysaccharides

Answer 10

Long chains of monosaccharides linked by glycosidic bonds; may be branched or unbranched

Question 11

Name some examples of polysaccharides.

Answer 11

Starch, glycogen, cellulose, and chitin

Question 12

Describe the structure/function of starch (including the polymers that form it)

Answer 12

Polysaccharide used for energy storage in plants
- Amylose: α-1,4-glycosidic bonds (linear, unbranched)
- Amylopectin: α-1,6-glycosidic bonds (branched)

Question 13

Describe the structure/function of cellulose

Answer 13

Polysaccharide that comprises the plants’ cell wall; provides structural support to the cell
- Formed by β-1,4-glycosidic bonds
- Opposing β-glucose can form parallel strands held together with hydrogen bonds
- Hydrogen bonds and 1,4 linkage of β-glucose make cellulose a strong, sturdy structure for plants

Question 14

Describe the structure/function of glycogen

Answer 14

Polysaccharide used for energy storage in animals
- Highly branched
- 1,4 linkage of α-glucose extensively branched through 1,6 linkage of α-glucose

Question 15

Describe the structure/function of chitin

Answer 15

Nitrogen-containing polysaccharide used for structural support in arthropods and in the cell walls of yeast and fungi
- Hydrophobic
- Contains hydrogen bonds

Question 16

Describe the general functions of carbohydrates (AKA why they are important)

Answer 16

1. Quick energy (mono and disaccharides)
   - Water soluble and contain many C-H bonds; easily transported and broken down
2. Storage (glycogen and starch)
   - Less soluble - better for storage
   - Can still be quickly converted to mono and disaccharides when necessary

Question 17

Why are polysaccharides like starch and glycogen used for energy storage?

Answer 17

Polysaccharides have many C-H bonds which store chemical energy. The more C-H bonds, the more energy can be stored.

Question 18

Describe the structural difference between starch and cellulose.

Answer 18

Starch is made out of a chain of α-glucose molecules and can be linear or branched. Cellulose is a chain of β-glucose molecules that can form hydrogen bonds between the chains to create orderly rows, creating a rigid, elongated structure.