Digestive system lab-- 11/07/11 and 11/08/11

Yesterday, we started a lab that had to do with our digestive system. We found out how acidic conditions affect protein digestion. We had four different test tubes: A, B, C and D. Each test tube had three cubes of egg white in them. In test tube A, we only put pepsin. This gave no immediate reaction. In test tube B, we added pepsin along with water. Similarly,this gave to immediate reaction either. Next, in test tube C, all we added was hydrochloric acid. Along with the other two, this had no immediate chemical reaction either. Lastly, we added hydrochloric acid along with pepsin. This also had no immediate chemical reaction, although there was a little steam coming up from it. Afterwards, we tested each of the formulas on litmus paper. A and B had no chemical reaction on the paper, but C and D had a pinkish, whitish tint to the litmus strip. Today, we went back to the tubes, and checked the egg white appearance and tested them out on litmus paper again. Same things were notified, except there were some small differences. This is like our digestive system in many ways. Formula D represents our stomach when it's healthy. The hydrochloric acid and pepsin are like the enzymes and acids in our stomach. The lower the pH, the more acidic.