Question

Which set of molecules is digested in human beings only in an alkaline medium?
(a)Diglycerides, maltose, disaccharides, starch
(b)Isomaltose, proteins, triglycerides, dipeptides
(c)Isomaltose, starch, DNA dipeptides
(d)Lactose, dipeptides, RNA, maltose

Answer 1

The pH of the medium is very important as the enzymes require a particular optimum pH for their functioning and get denatured if there is a change in the pH. This is seen in the case of the pepsin enzyme which digests proteins in the stomach only in the presence of acidic pH.

Complete answer:
The molecules that are digested only in alkaline medium include diglycerides, maltose, disaccharides, and starch. This is because diglycerides are digested by lipases into fatty acids and glycerol, maltose is digested into 2 molecules of glucose by maltase, and disaccharides are broken into monosaccharides in the alkaline pH of 7.8 in the small intestine. Starch is digested by the salivary amylase in the mouth which also has a 6.8 alkaline pH. Dipeptides are also digested in the alkaline pH of the small intestine, but they are digested by pepsin in the acidic pH of the stomach as well.

Additional Information: Let us look at the digestive enzymes produced in the alimentary canal.
-The enzyme salivary amylase is released along with saliva which is responsible for digesting 30% of the starch in the mouth.
-A proteolytic enzyme is released in the stomach known as pepsin which is responsible for digesting proteins into proteases and peptones. Lipases are also secreted in the stomach.
-The pancreatic juice consists of many enzymes such as trypsin, chymotrypsin, carboxypeptidases, amylases, lipases, and nucleases.
-The bile juice secreted by the liver does not contain any enzymes but helps in the emulsification of fats as well as activation of lipases.
-The intestinal juice also contains several enzymes such as disaccharidases (e.g., maltase), dipeptidases, lipases, nucleosidases, etc.
So, the correct option is ‘Diglycerides, maltose, disaccharides, starch’.

Note: -Saliva also contains an enzyme lysozyme which acts as an antibacterial agent and prevents mouth infections.
-Rennin is similar to pepsin and is found in the gastric juice of infants to digest the milk proteins.
-The bile juice contains bile salts, bile pigments, cholesterol, and phospholipids but no enzymes.