Which of the following juices contains the enzyme ptyalin?

Analyze the question: The question asks which digestive juice contains ptyalin. Ptyalin is an old name for an enzyme, so we need to know what it is and where it is found.

Explain the concept: Ptyalin is the older name for salivary amylase. It begins the digestion of starch in the mouth, breaking it down into the simpler sugar maltose.

Solution (checking each option):

• A. Gastric juice: Contains pepsin, rennin and hydrochloric acid. Pepsin digests proteins. No ptyalin here.
• B. Succus (succus entericus): This is intestinal juice. It contains maltase, sucrase, lactase, erepsin and lipase, which finish digestion. No ptyalin.
• C. Pancreatic juice: Contains pancreatic amylase (amylopsin), trypsin and lipase. The amylase is similar in function, but it is called amylopsin, not ptyalin.
• D. Saliva: Produced by the salivary glands. It contains salivary amylase (ptyalin). This is correct.

Answer: D. Saliva

Tip: Remember "Ptyalin = Palate/mouth." Ptyalin is the enzyme of the mouth, so it is found in saliva. Also remember these pairings for exams:

• Mouth: ptyalin (starch → maltose)
• Stomach: pepsin and rennin (proteins)
• Pancreas: amylopsin, trypsin, lipase
• Small intestine: maltase, sucrase, lactase, erepsin