Digestion and absorption

• What is the main purpose of digestion?

  To break down food into small molecules that can be absorbed by cells
• Why can't large biological molecules cross cell membranes?

  They are too big to be absorbed from the gut into the blood
• What happens to large biological molecules during digestion?

  They are broken down into smaller molecules like glucose that can cross cell membranes
• What are most large biological molecules classified as?

  Polymers
• What is the process called that breaks down polymers into smaller molecules?

  Hydrolysis reactions
• What do hydrolysis reactions do?

  They break bonds by adding water
• What are the products of carbohydrate digestion?

  Carbohydrates are broken down into disaccharides and then monosaccharides
• What are fats broken down into during digestion?

  Fatty acids and monoglycerides
• What are proteins broken down into during digestion?

  Amino acids
• What role do digestive enzymes play in digestion?

  They catalyze the breakdown of biological molecules in food
• What is amylase?


  A digestive enzyme that catalyzes the conversion of starch into disaccharides
• Where is amylase produced?

  In the salivary glands and pancreas
• What are membrane-bound disaccharidases?

  Enzymes attached to the cell membranes of epithelial cells that help break down disaccharides
• How do bile salts aid in lipid digestion?

  They emulsify lipids to form smaller droplets, increasing the surface area for lipase action
• What is the function of lipase?

  To catalyze the breakdown of lipids into monoglycerides and fatty acids
• What is the role of micelles in digestion?


  They help transport monoglycerides and fatty acids towards the epithelium for absorption
• How are amino acids absorbed in the ileum?

  Via co-transport with sodium ions through sodium-dependent transporter proteins
• What is the role of endopeptidases in protein digestion?

  They hydrolyze peptide bonds within a protein
• What is the function of exopeptidases?

  They hydrolyze peptide bonds at the ends of protein molecules
• What is the role of dipeptidases?

  They separate two amino acids that make up a dipeptide by hydrolyzing the peptide bond between them
• How is glucose absorbed in the ileum?

  By active transport with sodium ions via a co-transporter protein
• What is lactose intolerance caused by?

  An inability to break down lactose due to a deficiency of the enzyme lactase
• How are the digestion products of lactose absorbed across the epithelial cells?

  They are absorbed via specific transporter proteins in the epithelial cells
• What are the main digestive enzymes and their functions?

  • Amylase: Breaks down starch into disaccharides
  • Lipase: Breaks down lipids into monoglycerides and fatty acids
  • Endopeptidases: Hydrolyze peptide bonds within proteins
  • Exopeptidases: Hydrolyze peptide bonds at the ends of proteins
  • Dipeptidases: Hydrolyze dipeptides into individual amino acids
• What are the steps of digestion and absorption of nutrients?

  1. Large biological molecules are broken down into smaller molecules.
  2. Digestive enzymes catalyze the breakdown of these molecules.
  3. Products of digestion are absorbed across the ileum epithelium into the bloodstream.
  4. Specific transport mechanisms are used for different types of molecules (e.g., active transport, facilitated diffusion).