Module 2: Biological Molecules - Carbohydrates

Question 1

What are Carbohydrates?

Answer 1

Carbohydrates are molecules which consist only of Carbon, Oxygen and Hydrogen.

For every Carbon atom in the Carbohydrate there are usually two hydrogen atoms and one oxygen atom.

Question 2

What are the 3 types of Saccharides.

Answer 2

Monosaccharides.

Disaccharides.

Polysaccharides.

Question 3

What are Monosaccharides?

Answer 3

Monosaccharides are single sugar molecules and the simplest form of carbohydrates.

Question 4

What are some examples of Monosaccharides?

Answer 4

Glucose.

Fructose.

Galactose.

Ribose.

Question 5

What are Hexose sugars and give an example.

Answer 5

Hexose sugars are monosaccharides that have 6 Carbon atoms.

Example = Glucose.

Question 6

What are the 2 isomers of Glucose?

Answer 6

Alpha glucose.

Beta Glucose.

Question 7

What is the difference between alpha glucose and beta glucose?

Answer 7

The hydroxyl group on Carbon 1 for alpha glucose is below whereas in beta glucose the hydroxyl group is facing above.

Question 8

What are the properties of Glucose?

Answer 8

It is soluble in water. This is because glucose has a large number of hydroxyl groups (OH). These Hydroxyl groups can form hydrogen bonds with water molecules.

Its chemical bonds contains lots of energy.

The main energy source in animals and plants.

Question 9

What are Pentose sugars?

Answer 9

Pentose sugars are monosaccharides with 5 Carbon atoms

Question 10

What is Ribose.

Answer 10

It is a monosaccharide with 5 Carbon atoms.

Ribose is the sugar component of RNA nucleotides.

Question 11

What bonds join monosaccharides together?

Answer 11

Glycosidic bonds.

Question 12

Describe the formation of a Disaccharide.

Answer 12

During synthesis, a hydrogen atom on one monosaccharide bonds to a hydroxyl (OH) group on the other monosaccharides, releasing a molecule of water - this is a condensation reaction.

When water is added to a disaccharide, the glycosidic bonds breaks - this is a hydrolysis reaction.

Question 13

Which 2 monosaccharides forms Maltose?

Answer 13

Glucose + Glucose.

Question 14

Which 2 monosaccharides forms Sucrose?

Answer 14

Glucose + Fructose.

Question 15

Which 2 monosaccharides forms Lactose?

Answer 15

Glucose + Galactose.

Question 16

What are Polysaccharides?

Answer 16

They are formed when more than two monosaccharides join together.

Question 17

What are examples of Polysaccharides?

Answer 17

Starch in plants.

Cellulose in animals.

Glycogen in animals.

Question 18

What are the 2 different forms Starch exists in?

Answer 18

Amylose.

Amylopectin.

Question 19

Describe Starch.

Answer 19

It is the main energy storage material in plants. It is a mixture of 2 polysaccharides of alpha glucose - amylose and amylopectin.

Cells get energy from glucose and plants store excess glucose as starch. When a plant requires more glucose for energy, it breaks down the starch to release glucose.

Starch is insoluble in water. It doesn’t allow water to enter cells via osmosis. This is good for storage.

Question 20

Describe Amylose?

Answer 20

Long unbranched spiraling chains of alpha glucose. (1-4 glycosidic bonds).

The angles of the glycosidic bonds give it a coiled structure (cylinder-like). This makes it compact and good for storage as they can be packed.

Question 21

Describe Amylopectin.

Answer 21

It is a polymer of alpha glucose joined by 1-4 glycosidic bonds. They have a branch every 25-30 glucose molecules. (1-6 glycosidic bonds)

Long branched chain of alpha glucose. its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means that the glucose can be released quickly.

Question 22

Describe Glycogen.

Answer 22

It is a polysaccharide of alpha glucose.

It is the main energy storage material in animals. Animals store excess glucose as Glycogen.

Similar to Amylopectin but has more branches.
Loads of branches means that stored glucose can be released quickly. The glucose molecules at the branch points are joined by 1-6 glycosidic bonds.

It is a compact molecule which is good for storage

Question 23

Describe Cellulose.

Answer 23

It is a polymer of beta glucose. When a molecule of Cellulose is formed every second beta glucose molecule flips.. A glycosidic bond between 1-4 is formed.

It is the major component of cell walls in plants.

Its made of long unbranched chains of beta glucose. When beta glucose molecules bond, they form straight cellulose chains. The cellulose chains are linked together by hydrogen bonds to form strong fibres called Microfibrils.

The strong fibres mean cellulose provides structural support for cells. (e.g. in plant cell walls)

Question 24

Describe the structure of a Microfibril.

Answer 24

Microfibrils are primarily composed of long chains of a glucose polymer known as cellulose. Cellulose molecules consist of repeating glucose units linked together by β-1,4-glycosidic bonds.

Microfibrils are part of plant cells and give them support and shape, mainly found in the cell wall.