Carbohydrates (page 22 - 23)

Question 1

What are Carbohydrates made from?

Answer 1

Monosaccharides

Question 2

Most Carbohydrates are polymers, explain what a polymer is?

Answer 2

A polymer is a molecule made up of many similar, smaller molecules (called monomers) bonded together.

Question 3

The monomers that make up carbohydrates are called?

Answer 3

Monosaccharides.

Question 4

Explain why glucose is a hexose monosaccharide?

Answer 4

Glucose is a monosaccharide with six carbon atoms - this means its a hexose monosaccharide.

Question 5

What are the two forms of glucose?

Answer 5

Alpha (a) and beta (β). They both have a ring structure.

Look at diagram 1 on page 22, of the two types of glucose.

Question 6

Glucose’s structure is related to its function as the main energy source in animals and plants, do its structure make it a soluble? and why?

Answer 6

Yes its structure makes it soluble so it can be easily transported. Its chemical bonds contain lots of energy.

Question 7

Ribose is a monosaccharied with how many carbon atoms? name what it is called?

Answer 7

five carbon atoms - this means it’s a pentose monosaccharide. see structure diagram on page 22. - you need to know its structure.

Question 8

Ribose is what component of RNA nucleotides?

Answer 8

Ribose is the sugar component of RNA nucleotides (see page 34).

Question 9

All carbohydrates are made up of the same three chemical elements, name them?

Answer 9

Carbon (C)
Hydrogen (H)
Oxygen (O).

Question 10

For every carbon atom in carbohydrate there are usually what atoms?

Answer 10

two hydrogen atoms and one oxygen atom.

Question 11

Monosaccharides join together to form what?

Answer 11

Disaccharides and Polysaccharides

Question 12

How are Monosaccharides joined together?

Answer 12

they are joined together by glycosidic bonds.

Question 13

Explain the ‘condensation reaction’ during synthesis?

Answer 13

during synthesis, a hydrogen atom on one monosaccharide bonds to a hydroxel (OH) group on the other, releasing a molecules of water. - this is called a condensation reaction.

Question 14

what is the reverse of synthesis reaction called? and explain what happens

Answer 14

hydrolysis.

A molecule of water reacts with the glycosidic bond, breaking it apart.

Question 15

When is a disaccharide formed?

Answer 15

when two monosaccharides join together. look at diagram 3 on page 22 for the structure. you need to learn this.

Question 16

Sugar is a general term for what?

Answer 16

monosaccharides and disaccharides.

Look at diagram 3 on page 22 for example of glucose molecules.

Question 17

Two a-glucose molecules are joined together by a glycosidic bond to form maltose, (on diagram 3 page 22)

Other disaccharides are formed in a smilar way.

how is Surcrose disaccharide formed? and Lactose formed?

Answer 17

surcrose is a disaccharide formed when a-glucose and fructose join together.

and Lactose is a disaccharide formed by the joining together of either a-glucose of β-glucose and galactossee diagram 3 on page 22)

Question 18

Explain when a polysaccharide is formed?

Answer 18

when more than two monosaccharides join together.

look at diagram 4 on page 22.

Question 19

What is

Starch, Glycogen, and Cellulose?

Answer 19

Polysaccharides.

you need to know about the relationship between the structure and function of these three polysaccharides.

Question 20

What is Starch?

Answer 20

Starch is the main energy storage material in plants.

Question 21

Explain the function of starch?

Answer 21

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 22

Starch is a mixture of two polysaccharides of alpha-glucose, what are they called?

Answer 22

alpha-glucose

Amylose and amylopectin.

Question 23

Explain the function starch mixture of the two polysaccharides of alpha-glucose Amylose and Amylopectin polysaccharides?

Answer 23

Amylose - a long, unbranched chain of a-glucose. The angles of the glycosidic bonds give it a coiled structure, almost like a cylinder. This makes is compact so it’s really good for storage because you can fit more in to a small space. (see diagram 1 on page 23 of Amylose).

Amylopectin - a long, branched chain of a-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. (see diagram 2 on page 23).

Question 24

is Starch soluble or insoluble in water? explain why

Answer 24

Starch is insoluble in water - so it doesn’t cause water to enter cells by osmosis. (see page 58), which would make them swell. This makes it good for storage.

Question 25

Explain quickly what starch is?

Answer 25

Starch is the main energy storage material in plants.
cells get energy from glucose.
starch is a mixture of two polysaccharides of alpha-glucose - amylose and amylopectin.
starch is insoluble in water, so it doesnt cause water to enter cells by osmosis.

Question 26

What is Glycogen?

Answer 26

Glycogen is the main energy storage material in animals.

Question 27

Animal cells get energy from where?

Answer 27

glucose.

Question 28

Animals store excess glucose as …..

Answer 28

glycogen - another polyaccharide of alpha-glucose.

Question 29

Explain Glycogen structure?

Answer 29

its structure is very similar to amylopectin, (a long branched chain of a-glucose, except that it has loads more side branches coming off it. (loads of branches means that stored glucose can be released quickly, which is important for energy release in animals.

Question 30

Why is Glycogen a compact molecule?

Answer 30

so it’s good for storage.

Question 31

Explain quickly what Glycogen is?

Answer 31

Glycogen is Polysaccharide of alpha-glucose
the main energy storage material in animals
animal cellls get energy from glucose ad store glucose as glycogen.
its structure is similar to amylopectin except it has loads more side branches coming off, - stored glucose can be released quickly.
also very compace molecure so good for storage.

Question 32

What is Cellulose?

Answer 32

the major component of cell walls in plants

Question 33

What is Cellulose made of?

Answer 33

made of long unbranched chains of beta-glucose. (see diagram on page 23).

Question 34

When beta-glucose molecules bond what do the form?

Answer 34

they form straight cellulose chains.

Question 35

How are cellulose chains linked together?

Answer 35

they 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 36

Explain quickly what Cellulose is?

Answer 36

Cellulose is a Polysaccharide
its the major component of cell walls in plants.
made of long unbranched chains of beta-glucose
when beta-glucose molecules bond they form straight cellulose chains.
the chains link together by hydrogen bonds to form strong fibres called microfibrils. (structural support for cells).

Question 37

What is the structural difference between an alpha-glucose molecule and a beta-glucose molecule?

Answer 37

The sole chemical difference between alpha and beta glucose is the orientation of the -OH (hydroxel) and -H (hydrogen) groups on carbon 1.

Unlike beta glucose, which has its -OH group attached above the ring, alpha glucose has its -OH group linked below the ring.

Polysaccharides are formed by the codensation of many glusode units. glycogen and starch are formed by the condensation of a-glucose, Cellulose is formed by the condensation of β-glucose.

Question 38

Describe how glycosidic bonds are formed and broken in living organisms?

Answer 38

during the condensation reaction, a molecle of water is removed (from a ydroxyl group on one sugar and a hydrogen on another) and a glycosidic bond forms.

When polysaccharides are broken down during digestion, a hydroysis reaction occurs in which a water molecule is added to bread the glycosidic bond.

Question 39

Briefly describe the structure of starch?

Answer 39

Starch is a polysaccharide that is made up of glucose molecules. It consists of a large number of glucose molecules that are combined together via glycosidic bonds in straight or branched chains to form starch.

Question 40

What is the function of cellulose?

Answer 40

Cellulose primarily functions as a structural support for plant cells and is found primarily in plant cell walls.

Question 41

Mannose is a hexose monosaccharie.

Which of the following is most likely to give the chemical formula of a mannose molecule?

A) C⁵H¹⁰O⁵
B) C⁶H¹²O⁶
C) C⁶H¹²N⁶
D) C⁵H⁵O¹⁰

Answer 41

the answer is ‘B’

remember a hexose monosaccharide is one with six carbon atoms and carbohydrates don’t contain nitogen, so the chemical formular must be C⁶H¹²O⁶

Question 42

State the function of glycogen and explain how the structure of glycogen is linked to its function (3 marks)?

Answer 42

Glycogen is a polysaccharide of alpha-glucose, which is used to store excell glucose in animals (1 mark)
It has a branched structure, meaning glucose can be released quickly (1 mark).
It’s also a very compact molecule, so its good for storage (1 mark).

Question 43

Remember…… for page 22 and 23 (carbohydrates)

Answer 43

remember that condensation and hydrolysis reactions are the reverse of each other. You need to learn how maltose, sucrose and lactose are formed and broken down by these reactions. And don’t forget that starch is composed of two different polysaccharides….and that glucose exists in two forms.