Digestion & absorption 6.1

This subsection looks at the human digestive system, its parts and functions are in this topic. This includes digestive enzymes, their optimum conditions, substrates and products, as well as detailed structure of villi and microvilli in the small intestine. 

Key concepts 

Learn and test your biological vocabulary for 6.1 digestion and absorption using these flashcards.

Essentials - quick revision through the whole topic

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

Read the slides and look up any words or details you find difficult to understand.

Video tutorial

Watch the Screencast of a teacher drawing the diagram below.
This shows how to draw a simple diagram of the digestive system that can be drawn quickly and used in IB exams.

Summary list for 6.1 Digestion and absorption

  • The outline structure of the digestive system (skill - annotated diagram).
  • Food is mixed with enzymes and moved along by the contraction of circular and longitudinal muscle of the small intestine.
  • Enzymes (amylase, lipase and an endopeptidase) are secreted by the pancreas into the small intestine where they digest macromolecules ( starch, glycogen, lipids and nucleic acids) in food into monomers.
  • Tissue layers in the intestines include longitudinal and circular muscles, mucosa and epithelium.
  • The presence of Villi in the small intestines increases the surface area of epithelium and helps absorb the monomers formed by digestion and mineral ions and vitamins.
  • Different nutrients are absorbed into epithelial cells by different membrane transport mechanisms.


  • Apply knowledge of the process or digestion and absorption in the small intestine to the digestion of starch and the transport of maltose and glucose to the liver.
  • Describe your experience of the use of dialysis tubing as a model of the intestines.
  • Draw an annotated diagram of the digestive system.
  • Identify tissue layers in transverse sections of the small intestine.


Test yourself - multiple choice questions

This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding


Just for fun

A little bit of fun to revise the digestion topic. Can you make it to the leader board?
If you can't see the content below, please click this link to Digestion card match game