The enzyme that is present in the saliva is

Step 1: Analyze the question The question asks which enzyme is found in saliva, the fluid produced by the salivary glands in the mouth.

Step 2: Explain the concept Digestion begins in the mouth. Saliva contains an enzyme that starts the chemical breakdown of starch. Let's look at each option:

• A. Rennin: found in the stomach of young mammals (like calves and infants). It curdles milk protein (casein). Not in saliva.
• B. Lipase: digests fats. It is produced mainly by the pancreas (pancreatic lipase) and works in the small intestine. Not the typical saliva enzyme.
• C. Pepsin: found in gastric juice in the stomach. It digests proteins in an acidic medium. Not in saliva.
• D. Ptyalin: this is another name for salivary amylase. It converts cooked starch into maltose in the mouth, at a slightly alkaline or neutral pH.

Step 3: Solution

Starch → (ptyalin / salivary amylase) → Maltose

This is why a piece of bread or yam begins to taste slightly sweet if you chew it for a long time. The starch is being changed into the sugar maltose.

Step 4: Answer

Tip for the exam: Link each enzyme to its location:

• Mouth: ptyalin (salivary amylase), which acts on starch
• Stomach: pepsin and rennin, which act on protein
• Pancreas/small intestine: lipase, trypsin, and pancreatic amylase

A quick memory trick is "Ptyalin = Palate/mouth", so ptyalin goes with the mouth.