Digestion and absorption of carbs

• Which monosaccharides form maltose?

  Glucose + glucose
• Which monosaccharides form lactose?

  Galactose + glucose
• Which monosaccharides form sucrose?

  Glucose + fructose
• What is the process of digestion for complex dietary molecules?

  • Broken down into small molecules
  • Via digestive enzymes
  • Through hydrolytic cleavage
• What are carbohydrates classified as?

  • Group of organic compounds
  • Sugars/Saccharides
  • Starches
• What is the energy yield from the oxidation of carbohydrates?

  It yields energy
• Where does carbohydrate digestion primarily occur?

  • Mouth
  • Small intestine
• What are the sources of carbohydrates in our diet?

  Starch, lactose, sucrose, trehalose, cellulose
• What type of digestion occurs in the mouth?

  Mechanical and chemical digestion
• What enzyme is secreted by salivary glands?

  Salivary amylase
• What does salivary amylase hydrolyze?

  Starch into maltose and dextrin

  
• What is the pH in the mouth?

  ~ 6.8 – 7.0
• What percentage of starch is broken down in the mouth?

  About 5%
• What is the pancreatic enzyme involved in carbohydrate digestion?

  Alpha (α)-amylase

  
• What are the brush border enzymes involved in carbohydrate digestion?

  • Disaccharidases
  • Oligosaccharidases
  • Isomaltase
  • α (1,6) glucosidase
• What type of enzyme is pancreatic alpha amylase?

  It is an endoglycosidase
• What linkages does pancreatic alpha amylase act on?

  It acts on α1,4 linkages
• What are the hydrolytic products of pancreatic alpha amylase?

  Maltose, maltotriose, and α-limit dextrins

  
• What are the products generated from carbohydrate digestion?

  • Maltose
  • Maltotriose
  • α-limit dextrins
  • Glucose
  • Galactose
  • Fructose

  
• What are the types of carbohydrate digestion enzymes?

  • Salivary α-amylase
  • Pancreatic α-amylase
  • Disaccharidases
  • Isomaltase
  • Sucrase
  • Lactase
  • Trehalase

  
• What are the mechanisms of absorption for monosaccharides?

  • Passive diffusion
  • Facilitated diffusion
  • Active transport
• How do monosaccharides enter enterocytes?

  By passive diffusion and transporters
• What is the Na+ independent transporter for monosaccharides?

  GLUT5

  
• What is the Na+/glucose co-transporter for monosaccharides?

  SGLT1

  
• What are the major sources of polysaccharides?

  • Glycogen
  • Starch (amylose + amylopectin)
• Where does carbohydrate digestion not occur?

  In the stomach
• What inactivates salivary α-amylase in the stomach?

  Low pH in the stomach
• Where does carbohydrate digestion continue after the stomach?

  • In the small intestine
  • By pancreatic and brush border enzymes