Human saliva contains an enzyme that begins the digestion of starchy foods in the mouth. What is the name of this enzyme?

Introduction / Context:
Digestion of food in humans begins in the mouth, not only through chewing but also through the action of enzymes present in saliva. School biology textbooks emphasise that saliva contains a specific enzyme responsible for starting the breakdown of starch into simpler sugars. This question asks you to recall the name of that enzyme, which is a very common general knowledge item in human physiology.

Given Data / Assumptions:

• The site of action is the mouth, where saliva mixes with food.
• Starchy foods, such as rice, bread, and potatoes, are the main substrates initially affected.
• The options include salivary amylase (ptyalin), pepsin, trypsin, and pancreatic lipase.
• We assume standard knowledge of digestive enzymes and their locations.

Concept / Approach:
Salivary glands secrete saliva that contains the enzyme salivary amylase, also called ptyalin. This enzyme begins the digestion of carbohydrates by breaking down starch into maltose and smaller polysaccharides. Pepsin is a protein digesting enzyme found in the stomach, trypsin is a protein digesting enzyme secreted by the pancreas into the small intestine, and pancreatic lipase breaks down fats in the small intestine. Because the question explicitly refers to the enzyme in saliva that acts on starch, salivary amylase (ptyalin) is the correct answer.

Step-by-Step Solution:
Step 1: Recall that saliva is secreted by salivary glands in the mouth and mixes with food during chewing. Step 2: Know that the first chemical step in carbohydrate digestion occurs here, where an enzyme begins to break starch into simpler sugars. Step 3: Identify this enzyme as salivary amylase, also known by the older name ptyalin. Step 4: Compare this with other digestive enzymes: pepsin acts on proteins in the stomach, trypsin acts on proteins in the small intestine, and pancreatic lipase acts on fats. Step 5: Select salivary amylase (ptyalin) as the enzyme present in saliva that begins starch digestion.

Verification / Alternative check:
Experiments in school laboratories sometimes demonstrate how boiled saliva loses its ability to digest starch compared to fresh saliva, illustrating that an enzyme in saliva is responsible. Textbooks reinforce this by stating that salivary amylase converts starch into maltose, especially while food is still in the mouth or briefly in the upper oesophagus. They clearly separate this from pepsin, trypsin, and lipase, each of which is assigned to different parts of the digestive tract and different nutrients. This consistent explanation confirms that salivary amylase is the correct enzyme.

Why Other Options Are Wrong:
Pepsin is wrong because it is secreted by the stomach and acts mainly on proteins in acidic conditions, not on starch in the mouth. Trypsin is a pancreatic enzyme that continues protein digestion in the small intestine and is also not present in saliva. Pancreatic lipase is a fat digesting enzyme active in the small intestine, again unrelated to saliva or initial starch digestion. None of these alternatives fits the description of a salivary enzyme acting on carbohydrates.

Common Pitfalls:
A common pitfall is mixing up digestive enzymes and forgetting where each one acts. Students may remember that pepsin is a famous digestive enzyme and select it without noticing that the question is about saliva and starch. To avoid this, mentally organise enzymes by their location: salivary amylase in the mouth, pepsin in the stomach, pancreatic enzymes in the small intestine. This simple classification makes it much easier to choose salivary amylase as the correct answer for saliva related questions.

Final Answer:
The correct choice is Salivary amylase (ptyalin), which is the enzyme present in human saliva that begins the digestion of starchy foods in the mouth.