Concept: Enzyme: • Enzymes are biocatalysts and they catalyse the biochemical reactions both in vivo as well as in vitro. • They are highly specific to their substrate and have great catalytic power. • They enhance the rate of reaction tremendously without being changed. Explanation: Pancreas: • The pancreas is a compound (both exocrine and endocrine) elongated organ situated between the limbs of the ‘C’ shaped duodenum. • The exocrine portion secretes an alkaline pancreatic juice containing enzymes. • Pancreatic juice is released through the hepato-pancreatic duct. • The pancreatic juice contains inactive enzymes – trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases and nucleases. Lipase: • Fats are broken down by lipases with the help of bile into di-and monoglycerides. Thus, the enzyme lipase required for the digestion of fats is present in Pancreatic juice. Related Concepts: Saliva: • Saliva is mainly produced by three pairs of salivary glands, the parotids, the sub-maxillary and the sublingual. • These glands situated just outside the buccal cavity secrete salivary juice into the buccal cavity. • The saliva secreted into the oral cavity contains electrolytes and enzymes, salivary amylase and lysozyme. Gastric juice: • Pepsin, lipase, and rennin are all found in gastric juice. • Pepsin is secreted as inactive pepsinogen, which HCI activates. • Proteins are digested into peptones by pepsin. Intestinal juice: • The secretions of the brush border cells of the mucosa along with the secretions of the goblet cells constitute the intestinal juice. • This juice contains a variety of enzymes like disaccharidases (e.g., maltase), dipeptidases, lipases, nucleosidases, etc.