Digestive Process and Enzymes

Review

• What is the difference between physical digestion and chemical digestion?

• What is an enzyme?

• Why are enzymes specific to one substrate?

• Chemical digestion involves the hydrolysis of macromolecules in food

• Enzymes are required - why?

• Water is also required - why?

• Each digestive enzyme has a specific substrate (examples?)

• Each area of the digestive tract has a specific pH range; this is the optimal pH for enzymes that work there

• pH in the mouth is 7; in the stomach is 2; in the small intestine is 7 to 8

• HCl in gastric juice causes the low pH of the stomach

• required for the conversion of pepsinogen into pepsin

What other functions does the acidity of the stomach have?

• Digestive enzymes are produced by glands - where are these located?– mouth - salivary glands– stomach - gastric glands– pancreas – most cells of the pancreas – small intestine (intestinal glands in walls)

Name the enzymes produced by:

• Mouth– Salivary amylase

• Stomach– pepsin

• Pancreas– Pancreatic amylase, lipase, trypsin, nuclease

• Small intestine– Maltase, peptidase

Products

• What are the final products of digestion?

• glucose and other monosacharides, amino acids, fatty acids, glycerol, nucleic acids

Absorption

• How do nutrients get into the blood from the small intestine?– Absorbed through the cell membranes, by

facilitated transport

• Where does the blood go first, as it leaves the digestive tract?– Liver, via hepatic portal vein

• How do nutrients get into cells where they are needed?– Facilitated transport through cell

membranes

Which structure releases an enzyme that would catalyze the production of the above molecules?

a)Liver

b)Salivary glands

c)Pancreas

d)Stomach