1.1 Carbohydrates

Question 1

What is a monomer?

Answer 1

Subunit that repeats to form a polymer.

Question 2

What is a polymer?

Answer 2

Complex molecule formed with repeating units called monomers.

Question 3

Describe a condensation reaction

Answer 3

Condensation is the reaction that forms large, biological molecules.
The reaction releases water and bonds the smaller components together into larger molecules.

Question 4

Describe a hydrolysis reaction

Answer 4

Hydrolysis is the reaction that breaks down large, biological molecules.
The reaction requires water and splits larger molecules into their smaller components.

Question 5

Hydrolysis of proteins makes…

Answer 5

Amino acids

Question 6

Hydrolysis of polysaccharides makes…

Answer 6

Disaccharides and monosaccharides

Question 7

Hydrolysis of lipids makes…

Answer 7

Fatty acids and glycerol / monoglycerides

Question 8

Carbohydrates are made from which atoms?

Answer 8

Carbon, oxygen and hydrogen.

Question 9

What is an isomer?

Answer 9

Same molecular formula but different atom arrangement.

Question 10

What is the different between the isomers alpha and beta-glucose?

Answer 10

The OH (hydroxyl) groups are in a different orientation around C1.

Question 11

What is maltose made of?

Answer 11

Glucose + glucose

Question 12

What is sucrose made of?

Answer 12

Glucose + fructose

Question 13

What is lactose made of?

Answer 13

Glucose + galactose

Question 14

What is the bond between two monosaccharides?

Answer 14

Glycosidic bond

Question 15

How to test for reducing sugars?

Answer 15

• Add Benedict’s reagent
• Heat
• If reducing sugar present, turn from blue to orange/red

Question 16

How to test for non-reducing sugars?

Answer 16

Step 1: Boil in dilute HCl (to hydrolyse the non-reducing sugar).
Step 2: Neutralise the solution by adding sodium hydrogen carbonate.
Step 3: Add Benedict’s reagent and heat
The result will now be positive if a non-reducing sugar is present. Positive = change from blue to orange/red.
If the solution remains blue, then no sugar is present.

Question 17

Function of starch

Answer 17

Starch is the main energy storage material in plants. Can be hydrolysed to release glucose.

Question 18

How is starch structure suited to function?

Answer 18

• Insoluble so doesn’t affect water potential so water not drawn in by osmosis
• Large and insoluble so doesn’t diffuse out of cell
• Compact so a lot can be stored in a small space
• Has a branched form so has many ends that enzymes can simultaneously hydrolyse so quick release of glucose.

Question 19

How to test for starch?

Answer 19

• Add iodine solution
• If starch is present, colour will change from orange to blue-black.

Question 20

Function of glycogen

Answer 20

The main energy storage material in animals.

Question 21

How is the structure of glycogen suited to its function?

Answer 21

• Insoluble so does not affect water potential or draw in water via osmosis.
• Large so doesn’t diffuse out of cells
• Compact so can be stored in a small space
• More highly branched than starch so has ends that can be acted on simultaneously by enzymes to release glucose quickly.

Question 22

What is the function of cellulose and what is it made of?

Answer 22

Component of the plant cell wall and provides strength and rigidity. It is made of beta-glucose.

Question 23

What is cellulose structure and how is it suited to its function?

Answer 23

• Made of beta-glucose forming long, straight, unbranched chains.
• Cellulose chains run parallel to each other and are cross linked by hydrogen bonds which provide strength.
• These molecules are grouped to form microfibrils which in turn are grouped to form fibrils which provide strength.