Unit 1 Biological Molecules - Carbohydrates & Biochemical Tests

Question 1

What are monomers and polymers?

- Example of monomers

Answer 1

Monomers - Smaller units from which the larger molecules are made of
Polymers - Larger molecules from a large number of monomers joined together
EXAMPLES:
Monosaccharides
Amino acids
Nucleotides

Question 2

Describe what is meant by a Condensation reaction?

Answer 2

• Joins 2 molecules together which forms a chemical bond (glycosidic) and releases water

Question 3

Describe what is meant by a Hydrolysis reaction?

Answer 3

• Breaks a chemical bond between two molecules and involves the use of a water molecule

Question 4

Describe the 2 Structures of the glucose molecules.

Answer 4

• Glucose is a hexose sugar (C6H1206)
  -Has 2 isomers a-glucose and b-glucose
  ₂- The structures are:
  a-glucose

b-glucose

Question 5

Describe what is meant by monosaccharides?

Answer 5

- Monomers from which larger carbohydrates are made from
Examples -
GLUCOSE
FRUCTOSE
GALACTOSE

Question 6

Describe what is meant by disaccharides?

-& Examples

Answer 6

• Made from condensation 2 monosaccharides forming glycosidic bond
  Examples -
  MALTOSE = Glucose molecule + Glucose molecule
  SUCROSE = Glucose molecule + Fructose molecule
  LACTOSE = Glucose molecule + Galactose molecule

Question 7

Describe what is meant by polysaccharides?

-& Examples

Answer 7

- Made from the condensation of many glucose units forming glycosidic bonds
Examples - 
STARCH = condensation of a-glucose
GLYCOGEN = condensation of a-glucose
CELLULOSE = condensation of b-glucose

Question 8

Describe the structure of and basic functions of Glycogen.

Answer 8

• Contains 1,4 & 1,6 glycosidic bonds
• Condensation of a-glucose
• • Main energy store molecule in animals
• • Branches molecule

Question 9

Describe the adaptations of glycogen

Answer 9

Highly branched = Increases surface area for rapid hydrolysis of glycogen back to glucose for respiration
Insoluble = Does not affect water potential of cells
Compact molecule = Storage

Question 10

Describe the structure of and basic functions of Cellulose.

Answer 10

USED FOR CELL WALL IN PLANTS
condensation of b-glucose

• Contains 1,4 glycosidic bonds
• Long unbranched straight chains

Question 11

Describe the adaptations of cellulose.

Answer 11

Hydrogen bonds form strong fibres microfibrils and long chains = Provide structural support and high tensile strength
Insoluble = Does not affect water potential

Question 12

Describe the structure of and basic functions of Starch.

Answer 12

- Energy store in plants
- condensation of a-glucose
AMYLOSE
- Contains 1.4 glycosidic bonds
- Unbranched molecule
AMYLOPECTIN
- Contains 1,4 and 1,6 glycosidic bonds
- Branched molecule

Question 13

Describe the adaptations of starch.

Answer 13

Insoluble = will not affect water potential of cells
AMYLOSE
Coiled therefore compact = a lot of energy can be stored in a small space
AMYLOPECTIN
- Higly branched = increased surface are for rapid hydrolysis into glucose for respiration

Question 14

Describe the biochemical test for starch

Answer 14

1. Add iodine to the solution

ORANGE-BROWN to BLUE-BLACK = starch present

Question 15

Describe the biochemical test for reducing sugars

Answer 15

1. Add benedict’s reagent and heat at 100*C for 5mins
   BLUE to BRICK-RED = reducing sugar present

• the higher the conc. of sugar the redder it is
  blue↠green↠yellow↠orange↠brick-red

Question 16

Describe the biochemical test for non-reducing sugars

Answer 16

• Negative benedicts test = solution remains blue
  1. Boil with HCL acid in water bath to hydrolyse
  2. Cool the solution and add alkali to neutralise
  3. Add benedicts reagent & heat
  RED precipitate = non-reducing sugar present

Question 17

Describe the biochemical test for proteins.

Answer 17

BIURET test confirms presence of peptide bond
STEP 1
1. Add sodium hydroxide solution so solution is alkaline THEN COPPER SULFATE SOLUTION
2. Add biuret reagant
BLUE to PURPLE = protein present

Question 18

Describe the biochemical test for lipids.

Answer 18

1. Dissolve sample in ethanol
2. Add distilled water and shake
   WHITE EMULSION FORMS = lipid present