The enzyme which converts proteins into peptones is

Answer briefly: How does pepsinogen change into its active form?

Which of the following enzymes carries out the initial step in the digestion of milk in adult humans?

Bacteria present in contaminated food reaching the stomach are destroyed by:

$A$ young infant may be feeding entirely on mother's milk which is white in colour,but the stools which the infant passes out are quite yellowish. What is this yellow colour due to?

Protein digesting enzyme pepsin is secreted in . . . . . . part of the digestive system.