Digestion and absorption

• Digestion is the hydrolysis of large, insoluble molecules into small soluble molecules, so that they can be absorbed into the bloodstream
• faeces are undigested carbohydrates, proteins and fats
• the ph of the mouth is 7-8
• the ph of the stomach is 1
• the ph of the duodenum is 7-8
• the ph of the ileum is 7-8
• What enzyme is responsible for starch digestion in the mouth?

  Salivary amylase
• How does the mouth prepare food for swallowing?

  It sores food for easier swallowing
• Why is increasing the surface area of food important?

  It allows faster enzyme action
• What is one function of the stomach?

  Mixes and churns food
• What does the stomach produce to kill bacteria?

  Hydrochloric acid (HCl)
• What is gastric juice?

  Digestive secretion from stomach lining
• What is pepsin classified as?

  An endopeptidase
• What does pepsin hydrolyze?

  Specific internal peptide bonds
• What is the optimum pH for endopeptidase activity?

  1. 2
• Which macromolecules are not digested in the stomach?

  Starch and lipids
• What enzymes are not produced in the stomach?

  Amylase and lipase
• What is the function of the duodenum?

  Receives pancreatic juices and bile
• What stimulates the release of digestive juices in the duodenum?

  Acidity of chyme entering the duodenum
• What does the liver produce?

  Bile salts
• Where are bile salts stored?

  In the gall bladder
• What is the role of bile in digestion?

  Increases pH of acidic food
• What does the pancreas secrete into the duodenum?

  Pancreatic juice
• What does pancreatic juice contain?

  Enzymes and alkali
• What is the function of the small intestine (ileum)?

  Digestion and absorption of monomers
• What are the steps of digestion in the lumen of the small intestine?

  1. Dipeptidase hydrolyzes peptides
  2. Maltase hydrolyzes maltose to glucose
  3. Sucrose hydrolyzes sucrose to glucose and fructose
  4. Lactase hydrolyzes lactose to glucose and galactose
• How does the digestion of starch occur in the mouth?

  Salivary amylase hydrolyzes glycosidic bonds
• What happens to starch in the stomach?

  No starch is digested in the stomach
• What occurs in the duodenum regarding starch digestion?

  Pancreatic amylase hydrolyzes starch into maltose
• What happens in the ileum regarding maltose?

  Maltase hydrolyzes maltose into glucose
• What is the structure and function of enzymes involved in digestion?

  • Enzymes are bound to membranes of organelles
  • Products of reactions are close to epithelial cells
  • Specific processes transport products
  • Enzymes remain effective during digestion
• What is the structure of starch?

  • Polysaccharide made of alpha glucose
  • Joined by condensation reactions
  • Forms glycosidic bonds
  • Large and insoluble
• What are the roles of enzymes in digestion?

  • Hydrolyze macromolecules into monomers
  • Increase surface area for enzyme activity
  • Facilitate absorption into bloodstream