The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the α form. Which of the following could amylase break down?
a) starch and chitin
b) starch, amylopectin, and cellulose
c) glycogen and cellulose
d) cellulose and chitin
e) glycogen, starch, and amylopectin
The Correct Answer and Explanation is :
The correct answer is e) glycogen, starch, and amylopectin.
Explanation:
Amylase is an enzyme that catalyzes the breakdown of polysaccharides into smaller sugar molecules. It specifically breaks the α-glycosidic linkages between glucose monomers. For amylase to effectively break down a polysaccharide, the glucose units must be in the α (alpha) configuration, which means that the hydroxyl group on the first carbon of each glucose molecule is positioned below the plane of the ring.
Now, let’s examine each of the options:
- Starch and Chitin:
- Starch: Starch is a polysaccharide composed of glucose molecules linked by α-glycosidic bonds. Amylase can break down starch because it contains α-linkages.
- Chitin: Chitin is a polysaccharide found in the exoskeletons of arthropods and fungi. It is made up of N-acetylglucosamine (a derivative of glucose) linked by β-glycosidic bonds, not α-glycosidic bonds. Since amylase cannot break β-glycosidic bonds, it cannot break down chitin.
- Conclusion: This option is incorrect.
- Starch, Amylopectin, and Cellulose:
- Starch: As mentioned, amylase can break down starch, which contains α-glycosidic bonds.
- Amylopectin: This is a branched form of starch and also contains α-glycosidic bonds. Therefore, amylase can break down amylopectin as well.
- Cellulose: Cellulose is a structural polysaccharide found in plant cell walls, made up of glucose monomers linked by β-glycosidic bonds. Since amylase cannot break β-glycosidic bonds, it cannot break down cellulose.
- Conclusion: This option is incorrect.
- Glycogen and Cellulose:
- Glycogen: Glycogen is a highly branched polysaccharide found in animals, composed of glucose monomers linked by α-glycosidic bonds. Amylase can break down glycogen.
- Cellulose: As stated, cellulose contains β-glycosidic bonds, so amylase cannot break it down.
- Conclusion: This option is incorrect.
- Cellulose and Chitin:
- Cellulose and Chitin both contain β-glycosidic bonds. Amylase cannot break down either of these substances.
- Conclusion: This option is incorrect.
- Glycogen, Starch, and Amylopectin:
- Glycogen, Starch, and Amylopectin are all composed of glucose monomers linked by α-glycosidic bonds, making them substrates that amylase can break down.
- Conclusion: This is the correct answer.
Thus, the enzyme amylase can break down glycogen, starch, and amylopectin, all of which have glucose monomers connected by α-glycosidic bonds.