section 2: biological molecules - topic 3: carbohydrates

Question 1

most carbohydrates are …?

Answer 1

polymers.

Question 2

what 3 chemical elements are all carbohydrates made up of?

Answer 2

carbon.
hydrogen.
oxygen.

Question 3

how many of each element is in a carbohydrate?

Answer 3

every 1 carbon atom - 2 hydrogens & 1 oxygen.

Question 4

what are the monomers that make up carbohydrates called?

Answer 4

monosaccharides.

Question 5

name 2 monosaccharides.

Answer 5

glucose.
ribose.

Question 6

how many carbon atoms does glucose have?

Answer 6

6 carbon atoms.
(hexose monosaccharide)

Question 7

what are the 2 forms of glucose?

Answer 7

alpha.
beta.

Question 8

how many carbon atoms does ribose have?

Answer 8

5 carbon atoms.
(pentose monosaccharide)

Question 9

what is ribose?

Answer 9

the sugar component of RNA nucleotides.

Question 10

how are monosaccharides joined together?

Answer 10

by glycosidic bonds.

Question 11

describe the condensation reaction.

Answer 11

during synthesis, a hydrogen atom on 1 monosaccharide bonds to a hydroxyl (OH) group on the other, releasing a molecule of water.

Question 12

what is the reverse of the synthesis reaction?

Answer 12

hydrolysis.
^ a molecule of water reacts with the glycosidic bond, breaking it apart.

Question 13

how is a disaccharide formed?

Answer 13

when 2 monosaccharides join together.

Question 14

examples of disaccharides?

Answer 14

2 alpha glucose molecules are joined together by a glycosidic bond to form maltose.

sucrose = alpha glucose + fructose

lactose = either alpha or beta glucose + galactose

Question 15

how is a polysaccharide formed?

Answer 15

when more than 2 monosaccharides join together.

Question 16

example of a polysaccharide?

Answer 16

lots of alpha glucose molecules are joined together by glycosidic bonds to form amylose.

Question 17

what is starch?

Answer 17

the main storage material in plants.

cells get energy from glucose & plants store excess glucose as starch (when a plant needs more glucose for energy it breaks down starch to release the glucose).

Question 18

why is starch good for storage?

Answer 18

because it’s insoluble in water - so it doesn’t cause water to enter cells by osmosis (would make them swell).

Question 19

what is starch a mixture of?

Answer 19

2 polysaccharides:
amylose.
amylopectin.

Question 20

what is amylose?

Answer 20

a long, unbranched chain of alpha glucose.
the angles of the glycosidic bonds give it a coiled structure, almost like a cylinder.

this makes it compact - really good for storage as you can fit more into a small space.

Question 21

what is amylopectin?

Answer 21

a 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 a the glucose can be released quickly.

Question 22

what is glycogen?

Answer 22

the main energy storage material in animals.

animals store excess glucose as glycogen.

Question 23

what is the structure of glycogen?

Answer 23

very similar to amylopectin, but has loads more side branches coming off it.

Question 24

why is the structure of glycogen useful?

Answer 24

lots of branches means that stored glucose can be released quickly - important for energy release in animals.

it’s also a very compact molecule - good for storage.

Question 25

what is cellulose?

Answer 25

the major component of cell walls in plants.

Question 26

what is the structure of cellulose?

Answer 26

made of long, unbranched chains of beta glucose.

when beta glucose molecules bond, they form straight cellulose chains.
^ these are linked together by hydrogen bonds to form strong fibres (microfibrils).

Question 27

why is the structure of cellulose useful?

Answer 27

the strong fibres mean cellulose provides structural support for cells.