Answer
Tube 1: only water and protein exists, so no digestion takes place.
Tube 2: the enzyme pepsin will not digest the egg white since no HCl is present to break down the proteins.
Tube 3: the strong acid will denature the proteins, but does not actually digest anything for lack of pepsin
Tube 4: With pepsin and HCl, the egg white will be digested into peptides.
Work Step by Step
HCl, water, and pepsin are needed to break down and digest proteins.
