If you chew on a piece of bread long enough, it begins to taste sweet because
(a) Maltose is formed by maltase
(b) Fatty acids are formed by lipase
(c) Disaccharides are formed by breaking down of starches by amylase
(d) Glucose is formed from disaccharides

Hint: Food tastes sweet when there are short polymers of saccharides present such as monosaccharide or disaccharide in it. Normally food such as bread is made up of polysaccharides which do not taste sweet.

Complete Answer:
The bread tastes sweet after chewing it for a long time because of the digestion of polysaccharides into disaccharide maltose with the help of salivary amylase which is secreted along with the saliva. Only the digestion of sugars i.e. polysaccharides takes place in the mouth as only amylase enzyme is present in saliva. Maltose is formed by 2 molecules of glucose and thus is sweet in taste.

Additional information: Let us look at the digestion of sugars in our bodies.
- The digestion of sugars starts in the mouth by the action of salivary amylase.
- Further, the carbohydrates are hydrolyzed in the intestine by the action of pancreatic amylase which is released along with the pancreatic juice.
- Carbohydrate digesting enzymes are also present in the intestinal juice which is also known as succus entericus.
- The enzyme maltase breaks down maltose into 2 molecules of glucose.
- The enzyme lactase digests lactose to form glucose and galactose.
- The enzyme sucrase digests sucrose into glucose and fructose.
Glucose, fructose, galactose all are simple monosaccharides that are directly absorbed and utilized by cells.
So, the correct option is ‘(c) Disaccharides are formed by breaking down starches by amylase’.

Note:
- Another enzyme known as lysozyme is present in saliva which is an antibacterial agent thus preventing infections.
- The pH of saliva is around 6.8 which is optimal for the functioning of the enzyme salivary amylase.
- Saliva contains mucus in it which helps in the lubrication of food and making it into a bolus.