Anatomy and Physiology / Unit 9: The Respiratory and Digestive Systems
9.6 Digestive Enzymes and Chemical Digestion
Notes
Enzymes hydrolyze large food molecules into small ones. Each enzyme has an optimal pH.
- Carbohydrates to monosaccharides: salivary amylase (mouth) and pancreatic amylase start starch digestion; brush border enzymes (maltase, sucrase, lactase) finish. Lactose intolerance results from low lactase.
- Proteins to amino acids: pepsin (stomach, acidic) then trypsin and chymotrypsin (pancreas) and brush border peptidases.
- Fats to fatty acids and monoglycerides: bile emulsifies fat into droplets, then pancreatic lipase digests it.
- Nucleic acids by nucleases.
- Hormones: gastrin (stimulates stomach acid), secretin (pancreas releases bicarbonate), cholecystokinin (CCK) (gallbladder contracts, pancreas releases enzymes).
- Example: bile is not an enzyme; it physically breaks fat globules into smaller droplets, increasing the surface area for lipase.
Practice
Which enzyme begins the digestion of starch in the mouth?
Salivary amylase breaks starch into smaller sugars.
After a fatty meal, which hormone causes the gallbladder to contract?
CCK is released when fats enter the duodenum.
A person without a gallbladder has trouble digesting a very fatty meal. What is the best explanation?
Bile is stored in the gallbladder; without it, fat emulsification is reduced.
Ready for more? Take the Unit 9 test.