Carbohydrates

Question 1

What are monosaccharides?

Answer 1

Monomers from which larger carbohydrates can be made

Question 2

What are isomers?

Answer 2

Molecules with the same molecular formula, but arranged differently

Question 3

What are the four monosaccharide isomers?

Answer 3

Galactose, fructose, alpha glucose and beta glucose

Question 4

What does beta-glucose look like?

Answer 4

HO - H (bottom)

Question 5

Describe the structure of fructose

Answer 5

It has four carbons and one oxygen atom in its main structure

Question 6

What does galactose look like?

Answer 6

H - H (bottom)

Question 7

What does apha-glucose look like?

Answer 7

HO - OH (bottom)

Question 8

What monomers form the disaccharide maltose?

Answer 8

glucose + glucose

Question 9

What monomers form the disaccharide sucrose?

Answer 9

glucose + fructose

Question 10

What monomers form the disaccharide lactose?

Answer 10

glucose + galactose

Question 11

What is a condensation reaction?

Answer 11

A condensation reaction is when a molecule of water is eliminated to form a chemical bond between two molecules

Question 12

What is a disaccharide?

Answer 12

Two monosaccharides bond through a condensation reaction

Question 13

What is a hydrolysis reaction?

Answer 13

A reaction that breaks a chemical bond between two molecules and uses a water molecule.

Question 14

What bond is formed between monosaccharides after a condensation reaction?

Answer 14

Glycosidic bond

Question 15

Which bonds form coils?

Answer 15

Alpha, 1-4

Question 16

Which bonds form branches?

Answer 16

Alpha, 1-6

Question 17

What bonds form long, straight chains?

Answer 17

Beta, 1-4

Question 18

What monosaccharide is cellulose made from?

Answer 18

Beta- glucose monosaccharides

Question 19

What bonds are cellulose molecules joined with and why?

Answer 19

Beta-1,4-glycosidic bonds because it results in long, straight chains

Question 20

What bonds add to the rigidity of cellulose?

Answer 20

Microfibrils and macrofibrils held by hydrogen bonds

Question 21

What shape is glycogen and why?

Answer 21

It is coiled with 1-6 and 1-4 bonds for extra storage of energy as it is compact

Question 22

Why can’t glycogen escape the cell membrane?

Answer 22

Glycogen is a large molecule

Question 23

Why are polysaccharides insoluble?

Answer 23

If polysaccharides dissolve in the cell cytoplasm, they would decrease water potential. This would affect osmosis and thus the normal functioning of the cell.

Question 24

Why does glycogen have many alpha,1-6 glycosidic bonds for branching?

Answer 24

Glycogen can be hydrolysed more quickly to release glucose faster

Question 25

What is the difference between glycogen and starch?

Answer 25

Starch is found in plants, glycogen is found in animals

Question 26

What is osmotic lysis?

Answer 26

Bursting of the cell due to excess water moving in by osmosis

Question 27

Test for reducing / non-reducing sugars

Answer 27

How do we test for reducing sugars? 1. Prepare a beaker of fresh, boiling water as a water bath (to speed up the reaction with thermal energy) 2. Place 3cm^3 of the sample to a boiling tube, (water, grinded sample) add 3cm^3 of benedict's solution and place in the water bath 3. If there is no colour change, add HCl to a new sample 4. This will hydrolyse the sample and should break the glycosidic bonds to allow it to become monosaccharides 5. Slowly add 6cm^3 of sodium hydrogen carbonate in the heat to neutralise the acid (so benedict's solution can work effectively on it later on) 6. Test the solution using pH paper (e.g. litmus) 7. Add Benedict's solution 8. Blue to copper red would indicate the presence of a reducing sugar as the cu2+ ions would be reduced (they go blue to red, they lost electrons)

Question 28

What is the difference between amylose and amylopectin?

Answer 28

Amylose is unbranched and compact for extra storage of energy Amylopectin is branched with many side bonds for fast energy release

Question 29

What is the chemical formula for disaccharides?

Answer 29

C12H22O11

Question 30

What is the chemical formula for monosccharides?

Answer 30

C6H12O6

Question 31

What type of bonding is there between the chains of beta-glucose in cellulose?

Answer 31

Cellulose has many weak hydrogen bonds between the unbranched and straight chains of beta-glucose.

Question 32

Give 3 properties of glycogen

Answer 32

Insoluble, large, compact

Question 33

What is the role of glycogen and its location?

Answer 33

It is a storage molecule in animals

Question 34

How does the structure of glycogen aid with fast respiration?

Answer 34

There is a greater number of branches, so there are a greater number of ‘ends’ for the enzymes to attach to. A greater number of glucose molecules will be released