1.2-Monomers And Polymers

Question 1

1) What is a polymer?

Answer 1

A polymer is many monomers joined together

Question 2

2) Describe a condensation reaction

Answer 2

A condensation reaction joins two molecules together with the formation of a chemical bond and involves the production of a molecule of water.

Question 3

3) Describe a hydrolysis reaction

Answer 3

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

Question 4

1) Define a monosaccharide. Name the three monosaccharides you need to know and give their formula

Answer 4

Monosaccharides: a single carbohydrate unit which cannot be hydrolysed (broken down) to any simpler carbohydrate.
Glucose, galactose and fructose are examples – all have the formula C6H12O6

Question 5

3) Describe the reaction which forms a disaccharide.

Answer 5

Formed when two monosaccharides join together. A condensation reaction occurs, a water molecule is removed and a glycosidic bond is formed between the two monosaccharides.

Question 6

5) For each of the disaccharides you need to know (there are 3), write the monosaccharides they are formed from and the chemical equation for each.

Answer 6

Lactose C12H22O11: made of glucose and galactose.
Sucrose C12H22O11: made of glucose and fructose
Maltose C12H22O11: 2 a-glucose molecules joined together

Question 7

6) What is a polysaccharide?

Answer 7

Polysaccharides: are long chains of many monosaccharides joined together in condensation reactions with the formation of glycosidic bonds

Question 8

Starch

Answer 8

Starch
Found in plants used for storage
Made of alpha glucose
All the same way up
chains form a helical structure
Yes – holding the starch in the helical shape
1-4 glycosidic bonds and a few 1-6 glycosidic bonds.

Question 9

Glycogen

Answer 9

Found in Animals used for storage
Made of alpha glucose 
All the same way up
Helical with lots of branches
Yes – holding the glucogen in the coil
1-4 glycosidic bonds are formed and lots of 1-6 glycosidic bonds

Question 10

Cellulose

Answer 10

Found in Plants - strength in cell walls
Made of beta glucose

Long straight chains
Yes – MANY H-bonds between the chains forming microfibrils and fibrils
1-4 glycosidic bonds are formed

Question 11

1) Describe the difference in structure between starch and cellulose

Answer 11

• Starch is made of alpha glucose and cellulose is made of beta glucose.
• Starch is made of 1-4 glycosidic bonds and some 1-6 glycosidic bonds. Cellulose contains only 1-4 glycosidic bonds.
• Starch glucose monomers are the same way up. Cellulose glucose monomers are alternately inverted.
• Starch has a coiled structure whereas cellulose is made of long straight chains.
• Cellulose chains are held together by H-bonds forming microfibrils, but this doesn’t happen in starch

Question 12

1) How is the structure of starch related to its function?

Answer 12

• Compact storage molecule because of its helical structure
• Doesn’t affect osmosis because it is insoluble
• Cannot leave cells because it is a large molecule

Question 13

1) How is the structure of glycogen related to its function?

Answer 13

• Can be hydrolysed quickly because it has lots of branches so enzymes can act at the end of each branch
• Doesn’t affect osmosis because it is insoluble
• Is a compact storage molecule because it is tightly coiled

Question 14

1) How does the structure of cellulose relate to its function?

Answer 14

Long straight chains are joined together by MANY hydrogen bonds forming microfibrils. This provides strength to the cell wall.

Question 15

1) Describe the test for Reducing sugars

Answer 15

• Heat with Benedict’s solution. A red precipitate shows the presence of a reducing sugar

Question 16

1) Describe the test for non-reducing sugars

Answer 16

• Add HCl and heat
• Add sodium hydrogen carbonate to neutralise the acid.
• Add Benedict’s solution and heat.
• A red precipitate shows the presence of a reducing sugar

Question 17

1) Describe the test for starch

Answer 17

• Add iodine dissolved in potassium iodide.

* It turns Blue/Black if starch is present

Question 18

1) Describe how you would use colorimetry to identify the concentration of glucose in an unknown solution

Answer 18

1. Carry out the Benedict’s test on samples of glucose with a known concentration of glucose
2. Use a colorimeter to find the % light transmission of known samples of glucose
3. Draw a graph with glucose concentration on the x-axis and % light transmission on the y-axis
4. Plot the points on the graph and draw a calibration curve
5. Carry out the Benedict’s test on the solution of glucose with an unknown concentration
6. Find the % light transmission for this sample using the colorimeter
7. Find this % of light transmission on the y-axis and draw a horizontal line until you reach the calibration curve. Then draw a vertical line down and read the conc. of glucose from the x-axis