- Which one of the following is NOT produced by α- amylase digestion of ingested amylopectin
(1) Glucose (2) Maltose
(3) Maltotriose (4) α-limit dextrins
α-Amylase is an important digestive enzyme that hydrolyzes starch molecules such as amylopectin and amylose into smaller carbohydrates, facilitating their absorption in the human gastrointestinal tract. Amylopectin, a highly branched polysaccharide, is one of the two main components of starch. Understanding the specific products formed during α-amylase digestion of amylopectin is key for grasping the digestion and metabolism of complex carbohydrates.
Amylopectin and Its Structure
Amylopectin consists of glucose units linked primarily by α(1→4) glycosidic bonds, with branch points connected by α(1→6) glycosidic bonds approximately every 24 to 30 glucose residues. This branching is crucial because it affects how enzymes break down the polysaccharide.
Role of α-Amylase
α-Amylase acts on amylopectin by cleaving α(1→4) glycosidic bonds randomly, breaking down the long glucose chains into smaller oligosaccharides. However, it cannot cleave the α(1→6) bonds at the branch points; the result is a mixture of digestion products.
Major Products of α-Amylase Digestion of Amylopectin
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Maltose:
Maltose is a disaccharide consisting of two glucose units linked by α(1→4) bonds. It is one of the main products when α-amylase cleaves linear sections of amylopectin. -
Maltotriose:
Maltotriose contains three glucose units linked via α(1→4) bonds and is another common product formed by α-amylase action. -
α-Limit Dextrins:
These are branched oligosaccharides resulting from digestion stopping near an α(1→6) branch point. They are resistant to α-amylase and require other enzymes for further breakdown.
What Is NOT Produced?
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Glucose:
Free glucose is not a direct product of α-amylase digestion of amylopectin. Glucose is produced only after further enzymatic action by enzymes such as maltase and isomaltase that act on maltose, maltotriose, and α-limit dextrins.
Summary Table: α-Amylase Digestion Products of Amylopectin
Product Description Produced by α-Amylase? Maltose Glucose disaccharide formed from α(1→4) bonds Yes Maltotriose Glucose trisaccharide formed from α(1→4) bonds Yes α-limit dextrins Branched oligosaccharides near α(1→6) linkages Yes Glucose Monosaccharide sugar, product of further digestion No Conclusion
During α-amylase digestion of amylopectin, maltose, maltotriose, and α-limit dextrins are formed, but glucose is not directly produced. Glucose arises downstream through further actions of other enzymes.
Therefore, the correct answer is:
(1) Glucose -
