YUCK! My mouth did what? (Ryan Hainey)
Author:
Ryan Hainey
Principle(s) Illustrated
-pH
-Buffers
-Biochemistry
-Homeostasis
-Why is it that you can eat very acidic and basic substances without damaging your mouth or digestive tract?
Standards
LS1.A : Structure and Function
Feedback mechanisms maintain a living sy stem’s internal conditions within certain limits and mediate behaviors, allowing it to remain aliv e and functional ev en as external conditions change within some range. Feedback mechanisms can encourage (through positive feedback) or discourage (negative feedback) what is going on inside the living system. (HS-LS1-3)
Procedure:
1. Obtain 3-4 safe to consume substances. Preferably liquids or moist foods. Examples include coffee, orange juice, processed meats, etc.
2. Test and record the pH for each substance
3. Place the substance in your mouth for 20-30 seconds. Swoosh in mouth.
4. Spit the substance out and test the pH of the substance again.
5. Discuss any differences obtained in pH and reflect on why this has occurred.
Questioning Script
Prior knowledge & experience:
Students know from personal experience that the human mouth produces saliva, a weird liquidy substance that lubricates food for easy travel down the esophagus. They likely do not know the biochemistry occuring within saliva nor do they likely know what kinds of chemical reactions occur between saliva and food.
Root question:
What are the effects of human saliva on the biochemistry of foods and drinks?
Target response:
The human mouth operates as a buffer solution for foods and drinks entering the digestive tract. Alkaline and acidic substances placed in the mouth will change pH towards 7 because of the buffer activity of saliva.
For advanced students: The human mouth is a buffer solution because salivary enzymes such as amylase have optimal functional capacity at a pH of 7. At a high or low pH these enzymes will denature and cease to function. Thus the mouth has adapted saliva as a buffer solution to maintain the stability and functions of digestive enzymes.
Common Misconceptions:
-Saliva is only for lubrication
-Chemical reactions do not occur in our mouths
-Our mouth does not depend on pH