2.1.2 Biological Molecules - Carbohydrates

Question 1

What are the elements do carbohydrates only contain?

Answer 1

carbon, hydrogen, and oxygen

Question 2

Monomer to carbohydrates

Answer 2

1 unit = monosaccharide
2 units = disaccharide
2 or more units = polysaccharide

Question 3

What is the difference between alpha glucose and beta glucose?

Answer 3

Alpha glucose contains the OH on the bottom (right hand side of model) whilst Beta glucose has the OH at the top.
view diagram in notes

Question 4

Glucose:

Answer 4

• hexose monosaccharide
• soluble
• polar
• easily transported

Question 5

Why is glucose polar and soluble in water?

Answer 5

This is due to hydrogen bonds that form between the hydroxyl groups and water molecules.
Due to glucose being soluble it means that glucose is dissolved in the cytosol of the cell.

Question 6

What bonds form between two glucose molecules?

Answer 6

Glycosidic bonds

Question 7

What type of reaction takes place which causes water to form as a product?

Answer 7

Condensation reaction

Question 8

What type of reaction uses water to break bonds?

Answer 8

Hydrolysis reaction

Question 9

Ribose?

Answer 9

pentose monosaccharide

Question 10

glucose + glucose –>

Answer 10

Maltose

Question 11

galactose + glucose –>

Answer 11

Lactose

Question 12

glucose + fructose –>

Answer 12

Sucrose

Question 13

How does starch form?

Answer 13

Two polysaccharides of alpha glucose joined by glycosidic bonds.

Question 14

Starch?

Answer 14

Glucose made by photosynthesis in plant cells is stored as starch. It is a chemical energy store.
Amylose + amylopectin = starch

Question 15

Amylose:

Answer 15

Formed by alpha glucose molecules joined together only by 1,4 glycosidic bonds.
The angle of the bond causes this long chain of glucose to twist, to form a helix which is further stabilised by hydrogen bonding within the molecule.
Makes it more compact and much less soluble.

Question 16

Amylopectin:

Answer 16

Made by 1,4 glycosidic bonds between alpha glucose molecules, but there are also some glycosidic bonds formed by condensation reactions between carbon 1 and carbon 6 (so 1,6 glycosidic bonds present) on two glucose molecules.
This means that amylopectin has a branched structure.

Question 17

Benefits of Amylose?

Answer 17

• long, unbranched chain of alpha glucose
• coiled
• compact
• good for storage

Question 18

benefits of Amylopectin?

Answer 18

• long, branched chain of alpha glucose

- easy release of glucose as enzymes can reach the glycosidic bonds easily.

Question 19

What is the name of the energy storage molecule in animals and fungi?

Answer 19

Glycogen

Question 20

Glycogen:

Answer 20

• contains 1,4 and 1,6 glycosidic bonds
• forms more branches than amylopectin = more compact therefore less space is needed for it to be stored.
  this is important since animals are mobile.
• the branching also means there are many free ends where glucose molecules can be added or removed = speeds up the process of storing or releasing glucose molecules required by the cell.

Question 21

Cellulose:

Answer 21

• long, unbranched chains of beta glucose
• straight, linear chains
• cellulose chains linked together by hydrogen bonds => which form strong fibres called microfibrils
• the strong fibres means that cellulose structural support for cells