Human nutrition and digestion

Learning objectives

• Distinguish digestion from absorption.
• Relate digestive enzymes to substrates.
• Explain adaptations of the small intestine.

The big idea

A balanced diet supplies energy, building materials, fibre, water and micronutrients. Digestion breaks large food molecules into small soluble molecules; mechanical processing increases access without itself changing molecular identity.

Amylase, proteases and lipases act on different substrates. Bile emulsifies fats and helps neutralise acidic contents. Villi provide a large exchange area for absorption; assimilation is the later use of absorbed substances by cells.

Investigate and explain

Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.

No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.

Open the interactive investigation

Check your understanding