The gut and physical digestion

The times come from a teaching model: the protease digests the egg white only where it touches the solution, and that surface moves inwards by 0.05 mm a minute from every face. So a piece of side 10 mm lasts 100 minutes, 5 mm 50 minutes and 1 mm 10 minutes. A real tube of egg white and protease can take hours; the times change with the protease, the temperature and the shaking.

The egg white is drawn larger than true scale so that the pieces can be seen in the tubes. The magnified view is a schematic model: real protease molecules are far too small to see.

The crumbs are taken as cubes of 1 mm; real crumbs have every size and shape, so their surface area is given as about 60 cm².

With reduced motion the scalpel, the glass rod and the spatula do not move across the bench: each step shows its result straight away, and the pieces in the tubes still shrink with the stop-clock.