An information sheet about Digestive enzymes in the human body and the chemical digestion of a hamburger.

Digestive System:

Diagram of Digestive System of a Human
Comparing digestive systems of mammals
More comparisons of digestive systems.
A dissection of the digestive system of the laboratory rat, which are specially bred for scientific purposes, is an excellent way to learn about mammalian digestion. This practical exercise is optional, but it is also an excellent way to gain scientific skills of careful observation, identification of body parts and an understanding of the structure and function of the digestive system of mammals. If you plan to continue your science education at university, you will find this a valuable introduction to laboratory dissections. Make sure you read the practical instructions thoroughly, work slowly and carefully and document your progress with video or a digital camera. Remember that ‘dissection’ does not mean ‘to cut up’, it means ‘to expose to view’ - once something has been cut, it can’t be undone, so know what organ or tissue you are cutting and why.
Rat Dissection - Part 1: Exposing the Abdomen
Rat Dissection - Part 2: The Digestive System (Warning - graphic images)
Rat Dissection - Part 3: Identifying the organs of digestion.
What did you learn about dissection and the digestive system of a mammal? Compared to the length of the rat, how long was it’s alimentary canal? What was the difference in the wall of the stomach and the small intestine? What did you notice about the contents of the alimentary canal as they moved towards the rectum? What surprised you most about the inside of a rat?
Procedure for rat dissection.
Classification of the rat and glossary of terms (dorsal, ventral, thoracic etc.)
Check out Miss Baker’s Biology Blog, “Extreme Biology” for a video of a dogfish shark dissection.
Check out BBC Science and Environment News for a trip inside a python digesting a rat.
YouTube video - How Cells obtain their Energy


The main things to remember about enzymes are:
  1. Enzymes are proteins and biological catalysts.
  2. They are not used up in the reaction - only a small amount of enzyme is needed for each reaction.
  3. They do not change the amount of product formed
  4. They speed up a reaction, but do not change the direction of the reaction.
  5. They are very specific to their substrate and are often named according to the chemicals they work on.
  6. Enzymes, being proteins, are sensitive to heat, pH and heavy metal ions. When heat is applied the proteins are ‘denatured’ and no longer work.
In the human body there are several different enzymes including:
  • Amylase which works on starch
  • Maltase which works on maltose
  • Sucrase which works on sucrose
  • Lipasewhich works on lipids (Fats) and
  • Pepsin which works on polypeptides (Proteins)
More about Enzymes from Wikipedia here. Award-winning Enzyme Investigation here. Andrew Douch, a Biology teacher from Wanganui Secondary College, has produced many Biology podcasts, for students to learn about different topics - here is a link to his “Enzymatic” podcast. Andrew has also included some notes about enzymes here. Experiment with enzymes in liver here.