Carbohydrates 3.1.2

Question 1

What is a single monomer of a carbohydrate

Answer 1

Monosaccharide

Question 2

List four traits of monosaccharides

Answer 2

Sweet tasting
Soluble
Made of C, H and O atoms
Have the general formula (CH2O)n where n can be any number from 3-7

Question 3

What is the name given to a three carbon carbohydrate

Answer 3

Triose

Question 4

What is the name given to a six carbon carbohydrate

Answer 4

Hexose

Question 5

What is the name given to a five carbon carbohydrate

Answer 5

Pentose

Question 6

What two monomers make maltose

Answer 6

Glucose and glucose

Question 7

What two monomers make sucrose

Answer 7

Glucose and fructose

Question 8

What two monomers make lactose

Answer 8

Glucose and galactose

Question 9

What happened to disaccharides are in the presence of water

Answer 9

They hydrolyse into their constituent monosaccharides monomers. Within cells, these reactions are catalysed by specific enzymes

Question 10

What are two uses of polysaccharides

Answer 10

Storage molecules and structural support to plant cells

Question 11

Amylopectin is…

Answer 11

Branched. It had 1:4 and 1:6 glycosidic bonds

Question 12

Amylose is…

Answer 12

Unbranched. It has 1:4 glycosidic bonds

Question 13

Where is starch found

Answer 13

Starch is found in many parts of plants in the form of small granules or grains

Question 14

How do you test for starch

Answer 14

Apply iodine solution to the sample. If starch is present in the sample will stain deep blue

Question 15

How is starch suited to its role

Answer 15

• It is insoluble - So it does not affect water potential and water is not drawn into the cell by osmosis.
• It is large and insoluble - So it does not diffuse out of cells
• It is compact - So a lot of it can be stored in a small place.
• amylopectin has many ends - Each of which can be acted upon by enzymes simultaneously - So glucose monomers are released rapidly

Question 16

Where is glycogen found

Answer 16

Glycogen is found in animal and bacterial cells, but never plant cells. It is stored as small granules, mainly in muscles and the liver.

Question 17

How is glycogen suited to its role

Answer 17

• It is insoluble - So it does not affect water potential and water is not drawn into the cell by osmosis.
• It is large and insoluble - So it does not diffuse out of cells
• It is compact - So a lot of it can be stored in a small place.
• It is more highly branched than starch - So it has more ends which can be acted upon by enzymes simultaneously - So glucose monomers are released rapidly, which are used in respiration. This is important in animals as they have a higher metabolic rate and respiratory rate than plants because they are more active.

Question 18

How to Celulose differ from starch and glycogen

Answer 18

Celulose is formed from beta glucose molecules rather than alpha glucose molecules

Question 19

Describe the structure of cellulose

Answer 19

Celulose has straight, unbranched chains, running parallel to one another, allowing hydrogen bonds to form cross linkages between adjacent chains. Whilst each individual hydrogen bond as very little to the strength of the molecule, the sheer number of them overall, makes a significant contribution to strengthening the molecule and makes it a valuable structural material

Question 20

How are cellulose molecules arranged

Answer 20

Cellulose molecules are grouped together to form microfibrils, which are arranged in parallel groups called fibres

Question 21

How is Celulose suited to its function

Answer 21

• Cellulose molecules are made up of beta glucose - So form long straight, unbranched chains.
• Celulose molecular chains run parallel to each other and are cross-linked by hydrogen bonds - which add collective strength.
• Molecules are grouped to form microfibrils and then fibres - Which provides more strength.

Question 22

Test for reducing sugars

Answer 22

Add 2 cm³ of the sample to be tested to a test tube
Add an equal volume of Benedict’s reagent
Boil the mixture in a gently boiling water bath for 5 mins

Question 23

Test for non reducing sugar

Answer 23

Add 2 cm³ of the food sample to 2 cm³ of dilutes hydrochloric acid in a test tube and then place the test tube in a gently boiling water bath for five minutes.
Slowly add some sodium hydrogen carbonate solution to the test tube in order to neutralise the acid
retest the resulting solution by heating it with 2 cm³ of Benedict’s reagent and heat the mixture in a gently boiling water bath in five minutes