Topic 1.2 - Carbohydrates

Question 1

Monomers

Answer 1

smaller units from which larger molecules are made

Question 2

Monomers eg

Answer 2

Monosaccharides, amino acids
and nucleotides

Question 3

Polymer

Answer 3

Many monomers joined together

Question 4

Condensation reaction

Answer 4

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

Question 5

3) Describe a hydrolysis reaction

Answer 5

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

Question 6

Monosaccharides:

Answer 6

a single carbohydrate unit which cannot be hydrolysed (broken down) to any simpler carbohydrate.

Question 7

Eg of monosaccharides and formula

Answer 7

Glucose, galactose and fructose are examples – all have the formula C6H12O6

Question 8

3) Describe the reaction which forms a disaccharide.

Answer 8

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 9

Polysaccharides

Answer 9

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

Question 9

Disaccharides eg and formula

Answer 9

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

Question 10

Starch use

Answer 10

Found in plants
Storage molecule

Question 11

Starch made of which monomers

Answer 11

Alpha glucose

Question 12

Starch structure

Answer 12

Chains form a helical structure
Some branches

Question 13

H bonds in starch?

Answer 13

Yes holds the starch in place

Question 14

Glycogen use

Answer 14

Found in Nima’s
Storage molecule

Question 15

Glycogen monomers

Answer 15

Alpha glucose

Question 16

Glycogen structure

Answer 16

Helical
Lots of branches

Question 17

Glycogen H bonds?

Answer 17

Yes holds it in its helical shape

Question 18

Cellulose use

Answer 18

Found in plants
Provide strength to cell walls

Question 19

Cellulose monomers

Answer 19

Beta glucose
Every other beta glucose is inverted

Question 20

Cellulose structure

Answer 20

Long straight chains

Question 21

Cellulose H bonds?

Answer 21

Yes
Many between the long straight chains to form micro fibrils and fibrils

Question 22

Starch bonds that are present

Answer 22

Mainly 1-4 glycosidic bonds
Some 1-6 glycosidic bonds

Question 23

Glycogen bonds that are present

Answer 23

Mainly 1-4 glycosidic bonds
Lots of 1-6 glycosidic bonds

Question 24

Cellulose bonds that are present

Answer 24

Only 1-4 glycosidic bonds

Question 25

Describe the difference in structure between starch and cellulose

Answer 25

• Starch is made of alpha glucose whereas cellulose is made of beta glucose.
• Starch is made of mainly 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, helical structure whereas cellulose is made of long straight chains.
• Many hydrogen bonds between long straight chains in cellulose, but no hydrogen bonds between
  chains in starch

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Can be hydrolysed quickly because it has lots of branches, so enzymes can act at the end of each
branch
* Doesn’t affect osmosis/ water potential because it is insoluble
* Compact storage molecule because its helical structure

Question 28

How does the structure of cellulose relate to its function?

Answer 28

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

Question 29

12) Describe the test for Reducing sugars
*

Answer 29

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

Question 30

Describe the test for non-reducing sugars
*

Answer 30

Heat with Benedict’s solution and stays blue/negative
* Add HCl and heat
* Add sodium hydrogen carbonate to neutralise the acid.
* Add Benedict’s solution and heat.
* Brick red precipitate shows the presence of a reducing sugar

Question 30

Describe the test for starch
*

Answer 30

Add iodine dissolved in potassium iodide.
* It turns Blue/Black if starch is present

Question 31

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

Answer 31

1. Create a dilution series of glucose with known concentrations
2. For all known glucose concentrations, add Benedict’s solution and heat
3. Remove precipitate/ allow precipitate to settle and remove solution
4. Use a colorimeter to measure the % light transmission of known samples of glucose
5. Draw a graph with glucose concentration (units) on the x-axis and % light transmission on the y-axis
6. Plot the points on the graph and draw a line of best fit (calibration curve)
7. Carry out the Benedict’s test on sample of glucose with an unknown concentration à add Benedict’s
   solution and heat
8. Remove precipitate/ allow precipitate to settle and remove solution
9. Measure the % light transmission using a colorimeter
10. Find this % of light transmission on the y-axis and draw a horizontal line until you reach the
    calibration curve.
11. Then draw a vertical line down and read the concentration of glucose from the x-axis