Digestion and absorption

• What is the definition of digestion?

  Digestion is the process where large insoluble molecules are hydrolyzed into smaller soluble molecules that can be absorbed.
• What are the three main types of macromolecules involved in digestion for A Level Biology?

  • Carbohydrates
  • Lipids
  • Proteins
• What are the two types of enzymes mentioned that are important for digestion of carbohydrates?

  The two types of enzymes are amylases and membrane-bound disaccharidases.
• What does the suffix "ase" indicate in biology?

  The suffix "ase" indicates that the word refers to an enzyme.
• Where is amylase produced?

  Amylase is produced in the pancreas and the salivary glands.
• Where does the digestion of carbohydrates begin?

  The digestion of carbohydrates begins in the mouth.
• What does amylase hydrolyze carbohydrates into?

  Amylase hydrolyzes carbohydrates into disaccharides, such as maltose.
• What is the role of membrane-bound disaccharidases in digestion?

  Membrane-bound disaccharidases hydrolyze disaccharides into monosaccharides.
• What are two examples of membrane-bound disaccharidases?

  Two examples are sucrase and lactase.
• What do endopeptidases do in protein digestion?

  Endopeptidases hydrolyze peptide bonds between amino acids within the center of the polymer chain.
• What is the function of exopeptidases in protein digestion?

  Exopeptidases hydrolyze peptide bonds between amino acids at the ends of the polymer chain.
• Where does protein digestion begin?

  Protein digestion begins in the stomach.
• What is the role of lipase in lipid digestion?

  Lipase hydrolyzes the ester bonds in triglycerides.
• Where is lipase produced?

  Lipase is produced in the pancreas.
• What is the function of bile salts in lipid digestion?

  Bile salts emulsify lipids, splitting large droplets into smaller ones.
• Why is emulsification advantageous for digestion?

  Emulsification increases the surface area for faster hydrolysis by lipase.
• What are micelles and what is their role in lipid absorption?

  Micelles are spheres made of fatty acids, monoglycerides, and bile salts that deliver lipids to epithelial cells.
• How do fatty acids and monoglycerides enter epithelial cells?

  Fatty acids and monoglycerides enter epithelial cells by diffusion due to their nonpolar nature.
• What happens to fatty acids and monoglycerides once they enter the epithelial cells?

  They are reformed into triglycerides inside the Golgi apparatus or endoplasmic reticulum.
• What is a chylomicron?

  A chylomicron is a triglyceride combined with a protein.
• How are chylomicrons released from epithelial cells?

  Chylomicrons are released from epithelial cells by exocytosis.
• Where do chylomicrons go after being released from epithelial cells?

  Chylomicrons are absorbed into the lacteal and transported in the lymph.
• What are the key structures involved in the absorption of nutrients in the ileum?

  • Villi: folds of the ileum surface
  • Microvilli: further folds on the villi to increase surface area
  • Capillary network: maintains concentration gradient and short diffusion distance
• What are the mechanisms of absorption for monosaccharides and amino acids?

  • Absorbed by co-transport (active transport)
  • Some absorbed by facilitated diffusion
• What is the process of lipid absorption?

  1. Micelles deliver fatty acids and monoglycerides to epithelial cells.
  2. Fatty acids and monoglycerides diffuse through the plasma membrane.
  3. They are reformed into triglycerides inside the Golgi apparatus.
  4. Triglycerides combine with proteins to form chylomicrons.
  5. Chylomicrons are released by exocytosis into the lacteal.
• Lipase is an enzyme that breaks down fats into fatty acids and glycerol.
• Proteases are enzymes that break down proteins into amino acids.
• The large intestine absorbs water from undigested food, forming feces that are eliminated through defecation.
• The small intestine is the site of most nutrient absorption.