Exp. 10: Carbohydrates Hydrolysis

Starch

What is the most important source of carbohydrates in the human diet, accounting for more than 50% of carbohydrate intake?

Amylose

What polymer in starch is a linear polysaccharide composed entirely of D-glucose units joined by α-1,4-glycosidic linkages?

Amylopectin

What polymer in starch is a branched polysaccharide with glucose units linked primarily by α-1,4-glycosidic bonds and occasional α-1,6-glycosidic bonds?

Blue-black

What color appears when iodine reacts with amylose due to its coiled structure?

Reddish-brown

What color is observed when iodine reacts with amylopectin?

Amylase

What enzyme hydrolyzes starch into shorter polysaccharides, dextrins, maltose, and glucose?

Hydrolysis

What is the chemical reaction called where carbohydrates are broken down into glucose by reacting with water?

Glycogen

What is the energy reserve carbohydrate of animals, abundant in the liver and skeletal muscle cells?

Both are branched-chain polysaccharides, but glycogen is more highly branched.

What is the structural similarity between glycogen and amylopectin?

Reddish-brown

What color does glycogen produce when treated with iodine?

Glycolysis

What is the process in which glucose is broken down to produce energy?

Iodine Test

What test distinguishes starch from monosaccharides, disaccharides, and other polysaccharides using iodine?

Bluish-black color

In the iodine test, what indicates a positive result for starch?

Yellowish-brown color (no change)

What indicates a negative result for starch in the iodine test?

Amylase cannot attack the branching (1→6) linkages in glycogen.

During the hydrolysis of carbohydrates, why can't amylase fully digest glycogen?

(1) Formation of branched oligosaccharides

(2) Formation of dextrin, maltose, and glucose.

What are the two stages in the degradation of starch?

Deep blue-black color

What is the expected theoretical result of starch treated with Lugol's iodine at 0 minutes?

Reddish-brown color

What is the expected theoretical result of glycogen treated with Lugol's iodine at 0 minutes?

Blue color

What is observed at 6 minutes when starch is treated with Lugol's iodine during hydrolysis?

Yellowish-brown color

What is observed at 6 minutes when glycogen is treated with Lugol's iodine during hydrolysis?

Very pale blue or colorless

What is the final color change observed for starch after 12 minutes in the iodine test during hydrolysis?

Colorless

What is the final color change observed for glycogen after 12 minutes in the iodine test during hydrolysis?

Due to the strong complex formed between iodine and the coiled structure of amylose.

Why does starch show a deep blue-black color with iodine initially?

The branching in glycogen reduces iodine binding efficiency.

Why does glycogen produce a weaker color reaction with iodine compared to starch?