DIGESTION AND ABSORBTION

• What is the focus of Miss Estri's biology video?

  Digestion and absorption in A-level biology
• Why is it important to use specific keywords in biology?

  To ensure you earn marks on exams
• What is the definition of digestion?

  Hydrolysis of large insoluble molecules
• What happens to large insoluble molecules during digestion?

  They are hydrolyzed into smaller soluble molecules
• Which three types of macromolecules are digested?

  Carbohydrates, lipids, and proteins
• What are the two types of enzymes mentioned for carbohydrate digestion?

  Amylases and membrane-bound disaccharidases
• Where is amylase produced?

  In the pancreas and salivary glands
• Where does carbohydrate digestion begin?

  In the mouth
• What does amylase do to carbohydrates?

  Hydrolyzes polysaccharides into disaccharides
• What is the first part of the small intestine where digestion occurs?

  Duodenum
• What do membrane-bound disaccharidases do?

  Hydrolyze disaccharides into monosaccharides
• What are two examples of membrane-bound disaccharidases?

  Sucrase and lactase
• What do endopeptidases do?

  Hydrolyze peptide bonds within protein chains
• What do exopeptidases do?

  Hydrolyze peptide bonds at the ends of chains
• What are dipeptidases responsible for?

  Hydrolyzing peptide bonds between two amino acids
• Where does protein digestion start?

  In the stomach
• What is unique about lipid digestion?

  It involves both chemical and physical breakdown
• What enzyme is responsible for lipid digestion?

  Lipase
• What does lipase hydrolyze in triglycerides?

  The ester bond between glycerol and fatty acids
• What are bile salts produced and stored for?

  To emulsify lipids in the small intestine
• What is the advantage of emulsifying lipids?

  It increases surface area for digestion
• How does a larger surface area affect lipase action?

  It allows faster hydrolysis of lipids
• What are micelles?

  Spheres made of fatty acids and monoglycerides
• How do micelles help in absorption?

  They deliver fatty acids to epithelial cells
• What is the role of villi in the ileum?

  To increase surface area for absorption
• What are microvilli?

  Further foldings on villi to increase surface area
• How are monosaccharides and amino acids absorbed?

  By co-transport, a type of active transport
• What happens to lipids after they enter epithelial cells?

  They are reformed into triglycerides
• What is a chylomicron?

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

  By exocytosis
• Where do chylomicrons go after being released?

  Into the lacteals or lymph vessels
• How do lipids eventually enter the bloodstream?

  Through the capillary system from lymph
• What is the first step in digestion?


  Mouth
• What are the key processes involved in digestion and absorption?

  • Digestion: Hydrolysis of macromolecules
  • Absorption: Uptake of small molecules
  • Involves enzymes and physical processes
  • Occurs in the small intestine
• What are the differences between the digestion of carbohydrates, proteins, and lipids?

  • Carbohydrates: Hydrolyzed by amylases and disaccharidases
  • Proteins: Hydrolyzed by peptidases (endo and exo)
  • Lipids: Involves lipase and bile salts for emulsification
• What enzyme breaks down carbohydrates in the mouth?


  Amylase
• What is the significance of the villi and microvilli in the ileum?

  • Increase surface area for absorption
  • Contain capillary networks for efficient transport
  • Facilitate rapid uptake of nutrients
• How does co-transport work in nutrient absorption?

  • Involves active transport mechanisms
  • Allows absorption of glucose and amino acids
  • Maintains concentration gradients for nutrients
• What type of environment is present in the stomach?


  Acidic (pH 2)
• What is the role of bile salts in lipid digestion?

  • Emulsify lipids into smaller droplets
  • Increase surface area for lipase action
  • Facilitate absorption of fatty acids and monoglycerides