Qualitative Analysis of Carbohydrates

What percentage of starch is composed of amylopectin?

Which color indicates the presence of glycogen when using the iodine test?

What is the main structure responsible for the deep blue color observed in the presence of iodine?

What color is observed when iodine interacts with dextrin?

What type of bond links the D-glucose units in dextrins?

Which reagent is used to prepare the iodine solution for testing starch?

What precipitate is formed when basic lead acetate is added to starch paste?

What is the end product of complete hydrolysis of starch?

What does a faint brown color indicate in the iodine test?

Which polysaccharide is primarily found in all plant seeds for energy storage?

Qualitative Analysis of Carbohydrates (Polysaccharides)

Starch: Used for energy storage in plants.
- Found in all plant seeds.
- Composed of two subunits:
  - Amylose: 20% (inner layer)
  - Amylopectin: 80% (outer layer)
- Complete hydrolysis (breakdown) of both amylose and amylopectin by amylase enzyme or acid yields only D-glucose.
Dextrins: Low molecular weight carbohydrates produced by the hydrolysis of starch or glycogen.
- Mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic bonds.
- Most can be detected with iodine solution.

Iodine Test

Used for the detection of starch in solution.
Principle:
- Amylose in starch forms a deep blue color in the presence of iodine.
- Iodine molecule slips inside of the amylose coil.
Procedure:
1. Take 5 ml of solution in a test tube.
2. Add a few drops of iodine.
Results:
- Blue-black color: Indicates presence of starch (polysaccharide)
- Violet color: Indicates presence of dextrin
- Red color: Indicates presence of glycogen
- Faint brown color: Indicates presence of cellulose

Basic Lead Acetate Test

Used for the detection of starch in the solution.
Reagent: Basic lead acetate (NaOH + (CH3COO)2Pb)
Principle:
- Addition of lead acetate to starch paste leads to the formation of a white precipitate.
- This is discriminative for starch due to its high molecular weight.
Procedure:
1. Add 3 ml basic lead acetate to 2 ml of starch or dextrin paste.
Result: A white precipitate is observed only with starch.

Explore the qualitative analysis of carbohydrates, focusing on polysaccharides such as starch and dextrins. Understand the structure, hydrolysis process, and iodine test for detecting starch in solutions. This quiz aims to enhance your knowledge of carbohydrate chemistry and its applications.