Carbohydrases break down carbohydrates to simple sugars. Amylase is a…

The idea

Carbohydrases are enzymes that catalyse the hydrolysis of carbohydrates into simple sugars. Digestion converts large, insoluble food molecules into small, soluble molecules that can be absorbed across the gut wall. Amylase is a specific carbohydrase that breaks down starch, a polysaccharide, into simpler sugars such as maltose and eventually glucose. Starch is a polymer of glucose joined by glycosidic bonds; hydrolysis uses water to split these bonds. Amylase is produced in the salivary glands and pancreas, and works in the mouth and small intestine. Its active site is complementary to starch, so it is specific.

What earns the marks

• Carbohydrases are enzymes that catalyse the breakdown of carbohydrates into simple sugars.
• Amylase is a carbohydrase that specifically breaks down starch.
• Starch is a polysaccharide made of glucose units joined by glycosidic bonds.
• Digestion is hydrolysis: water is used to split bonds, producing smaller soluble sugars.
• Amylase is produced in salivary glands and the pancreas and acts in the mouth and small intestine.
• Enzyme specificity means amylase's active site is complementary to starch, not to all carbohydrates.

Common mistakes and how to put them right

• Saying carbohydrases break carbohydrates into amino acids.

  Put it right: They produce simple sugars such as glucose and maltose.

• Confusing amylase with protease or lipase.

  Put it right: Amylase acts on starch, a carbohydrate.

• Writing that enzymes are used up in the reaction.

  Put it right: Enzymes are biological catalysts and are not consumed, so they can be reused.

Exam tips

• Name the substrate and product for amylase explicitly: starch to simple sugars such as maltose and glucose.
• Use the term hydrolysis when explaining breakdown, and state that water is used.
• Link enzyme specificity to the complementary active site rather than saying enzymes 'fit' any substrate.