1.2 CARBOHYDRATES

Question 1

What are monosaccharides?

Answer 1

Monomers from which carbohydrates are made.

Question 2

What are some examples of monosaccharides? (3)

Answer 2

• Glucose
• Fructose
• Galactose

Question 3

How do you join two monosaccharides together?

Answer 3

A condensation reaction

Question 4

What is the bond between two monosaccharides called?

Answer 4

Glycosidic bond

Question 5

What is a disaccharide?

Answer 5

Two monosaccharides joined together by a glycosidic bond.

Question 6

What is maltose made of?

Answer 6

Glucose & Glucose

Question 7

What is sucrose made of?

Answer 7

Glucose & Fructose

Question 8

What is lactose made of?

Answer 8

Glucose & Galactose

Question 9

What is the difference between the 𝛂/β glucose structures?

Answer 9

(see notes for image)

𝛂: hydroxyl group below the oxygen
β: hydroxyl group above the oxygen

Question 10

What is a polysaccharide?

Answer 10

Multiple monosaccharides joined together by glycosidic bonds.

Question 11

What is cellulose made of?

Answer 11

chains of β glucose

Question 12

What is starch/glycogen made of?

Answer 12

chains of 𝛂 glucose

Question 13

What is the structure of starch?

Answer 13

• Has unbranched glucose chains, so compact.
• Also has some branched glucose chains.
• Very compact structure

Question 14

What is the function of starch?

Answer 14

• Insoluble and big so can be stored.
• Compacts so lots can be stored in small places
• Branched glucose chains allow enzymes to act of them quickly, to release lots of glucose.
• Used for storage in plants

Question 15

What is the structure of glycogen?

Answer 15

• Has very branched glucose chains.

- Has unbranched glucose chains, so compacted.

Question 16

What is the function of glycogen?

Answer 16

• Storage molecule for animals.
• Insoluble and big so can be stored.
• Compacts so lots can be stored in small places
• Branched glucose chains allow enzymes to act of them quickly, to release lots of glucose.

Question 17

What is the structure of cellulose?

Answer 17

• Straight, unbranched chains.

- Chains run parallel to one another.

Question 18

What is the function of cellulose?

Answer 18

• Chains running parallel are held together by H bonds.
• Makes these chains very strong.
• Cellulose molecules can clump together into fibres to make them stronger.
• Used for plant cell walls.

Question 19

Outline the test for reducing sugars

Answer 19

1. Add x volume of sample into test tube.
2. Dissolve this in water.
3. Add an equal (x) volume of Benedicts reagent.
4. Heat the mixture for 5 minutes.

Question 20

What are the observed colour changes for the reducing sugars test?

Answer 20

blue (no reducing sugars)

green - red (reducing sugars)

Question 21

Outline the test for non-reducing sugars?

Answer 21

1. Add x volume of sample into equal volumes of HCl.
2. Heat in a water bath for 5 minutes.
3. Add NaHCO₃ to neutralise the acid.
4. Then carry out the reducing sugars test on this sample.

Question 22

Why do you add HCl to you non-reducing sugar sample first?

Answer 22

HCl hydrolysed the polymer, breaking it up into its reducing sugar monomers.

Question 23

What is a reducing sugar?

Answer 23

A sugar that can donate electrons.

Question 24

Which sugars are reducing?

Answer 24

• All monosaccharides

- Maltos & Lactose (disaccharides)

Question 25

Outline the test for starch

Answer 25

1. Add iodine/potassium iodide to a crushed up sample.

2. If starch is present, the area with iodine/iodide will turn from yellow - blue/black.