Question

What are enzymes? Name an enzyme that is present in saliva and state its function.

Answer 1

Hint: Enzymes are ubiquitous substances that are required for speeding chemical reactions. Our body’s saliva is one of the most important components required for the digestion of food as it contains enzymes.

Complete answer:
 - Enzymes are protein molecules or macromolecules that act as biological catalysts that accelerate chemical reactions that occur in biological environments. The molecules that enzymes work on are substrates.
- Factors involved in the optimal working of the enzyme are pH, temperature, the concentration of the substrate, presence of inhibitors, competitors, etc.
- Saliva contains enzymes that break down the food we ingest and chew. An important enzyme is an amylase, also known as ptyalin.
- The enzyme breaks down starch into simpler sugars or polysaccharides such as maltose and dextrin. These broken down components are further digested in the small intestine.
- Amylase works optimally at the pH of 6.8.

Additional Information:
- About $30\%$ of the starch digestion occurs in the mouth cavity.
- The human saliva contains water, electrolytes, mucus, epithelial cells, enzymes apart from amylase such as lipase, some antimicrobial agents, lysozymes, etc.
- Apart from the presence of enzymes, the saliva helps in lubricating the food for its entry into the alimentary canal.
- Lack of saliva in the mouth is a characteristic of dehydration.

Note:
- Amylase also has an important role in protecting the teeth in the oral cavity from decay as they break down starchy food particles present between gaps of teeth, preventing microbial action on them.
- Almost all enzymes are protein, with the exception of ribozymes that are RNA-based enzymes.