Experiment #10: HYDROLYSIS OF STARCH ( ACID-CATALYZED) Flashcards
Common name to a white, granular or powdery, odorless, tasteless, complex carbohydrates
Starch
Formula of Starch
(C6 H10 O5)x
Starch is abundant in the ____ of _____ and in _____ and _______
seeds, cereal plants, bulbs, tubers
Starch is a ________ found in ______ and deposited in the form of _______ in the______ of the cell
Complex polysaccharide, plants, large granules, cytoplasm
2 Components of starch
Amylose, amylopectin
The _____ of ______ linked in a ______ by _______ . It has ______ ends and _____ end
Amylose, D-glucose units, linear fashion, a 1-4 linkages. 2 non-reducing, a reducing
Branched polysaccharide
Amylopectin
In these molecules, shorter chains of glucose units linked by _______ are also joined to each other by _______
a-1,4 linkages, a- 1,6 linkages
What happens to starch when placed in a boiling water
Granules rupture, forming a paste that gels on cooling
When a small amount of starch is added to the large amount of boiling water,a______ in water is formed
Colloidal dispersion of starch
Starch gives a characteristic _______ with ______
Deep blue color, iodine
Used to detect the presence of starch
Iodine test
When starch is hydrolyzed it forms
Dextrins (amylodextrin, erythrodextrin, achrodextrin), maltose then glucose
Iodine test is the test for the_________ with a _______ result
Presence of starch, blue- black positive
Starch (insoluble)
Blue-black/dark blue/ blue
Starch(soluble)
Blue-black/dark blue/blue
Amylodextrin
Blue-purple/ purple
Erythrodextrin
Red
Achrodextrin
No color/colorless
Maltose
No color
Glucose
No color
When the hydrolysis of starch is complete
The starch solution is colorless once 2 drops of iodine solution is added. The hydrolysis of starch does not occur immediately. The result of the test turns to black to dark purple before it becomes colorless
How is complex structure of starch is broken down into a simple carbohydrate, the glucose
Starch (C6 H10 O5) forms dextrins (amylodextrin, erythrodextrin, achrodextrin). Then it slowly forms maltose and finally glucose C6 H12 O6
Role of Hydrochloric Acid in Starch Hydrolysis
Acid caused scission of the glycosidic linkages, altering the structure and properties of the starch
Destroys the microcrystals in the starch, hydrolyze the glycosidic bond,
decrease the amount of amylopectin
Positive result of Lugol’s test
Blue-black/black
Presence of Glucose in Lugol’s test
Colorless
Negative result in Lugol’s test
Yellow
