absorption in the small intestine

• What is the primary function of the small intestine?

  To absorb the products of digestion
• How are large food molecules broken down during digestion?

  By enzymes into smaller molecules
• What enzyme digests starch into simple sugars?

  Amylase
• Where are the products of digestion absorbed?

  In the small intestine
• How long is the human small intestine?

  Around 5 meters
• Why is the length of the small intestine important?

  It provides a large surface area for absorption
• What structures cover the interior of the small intestine?

  Millions of villi
• How do villi contribute to absorption?

  They massively increase the surface area
• What are microvilli?

  Small projections on the surface of villi
• How do microvilli affect absorption?

  They increase the surface area even further
• Why is a good blood supply important for villi?

  It rapidly removes products of digestion
• What effect does a good blood supply have on concentration gradient?

  It increases the concentration gradient
• What ensures a short diffusion path in the small intestine?

  A thin membrane under the villi
• How do these adaptations affect the rate of diffusion?

  They ensure a rapid rate of diffusion
• What happens to molecules that cannot be absorbed by diffusion?

  They are absorbed by active transport
• What topic will have plenty of questions related to the small intestine adaptations?

  The adaptations of the small intestine
• What are the adaptations of the small intestine for absorption?

  • Long length (around 5 meters)
  • Millions of villi increase surface area
  • Microvilli further increase surface area
  • Good blood supply enhances absorption
  • Thin membrane ensures short diffusion path
  • Active transport for non-diffusible molecules