Question

If salivary amylase is lacking in the saliva, which of the following events in the mouth cavity will be affected?

• A. Proteins breaking down into amino acids.
• B. Starch breaking down into sugars.
• C. Fats breaking down into fatty acids and glycerol.
• D. Absorption of vitamins.

Answer 1

The correct option is B Starch breaking down into sugars.

Hint - Digestion of food starts from the mouth itself because of the presence of salivary amylase in saliva.

Part 1 - Structure of starch

• Starch is a heteropolysaccharide made up of two chains - Amylose and Amylopectin.
• Amylose is made up of straight-chain polymer of $\alpha -$D Glucose and Amylopectin is made up of branched-chain polymer of $\alpha -$D Glucose.

Part 2 - Action of Salivary amylase

• The salivary amylase is secreted by the salivary glands (like - Parotid gland, Sublingual gland, and Sub-maxillary gland).
• It acts on the $\alpha 1\to 4$ linkage present in amylose and amylopectin.
• Thus, break the starch by producing small chain polysaccharides and disaccharides like $\alpha$-Dextrin and Maltose.

Part 3 - Conclusion

• Salivary amylase cannot act upon the breakdown of proteins, fats, and the absorption of vitamins.
• Salivary amylase can only digest the starch into smaller sugar molecules.
• Thus, if salivary amylase is not present in the saliva then the starch digestion in the mouth would not take place.

Final step - If salivary amylase is lacking in the saliva, only starch breakdown will be affected.