Preview - Exploring Homeostasis And Feedback Loops With Diabetes

Does the human body maintain a stable pH?

For this investigation, you are testing whether or not the human body maintains a stable pH as external conditions change.  To help you design your experiment, read the purpose and materials list below: 

Purpose:

The purpose of this investigation is to see if the pH of a living system maintains stability as external conditions change.  

Materials:

  • 2 cups of distilled water (no more than 25 mL per cup)
  • 2 cups of living homogenate (no more than 25 mL per cup)
  • 1.0M solution of HCl (Hydrochloric Acid, a strong acid)
  • 1.0M solution of NaOH (Sodium Hydroxide, a strong base)
  • 2 droppers
  • pH strips/pH meter 

NOTE: 

  • The pH scale is a logarithmic scale which measures how acidic/basic a solution is and ranges from 0 to 14.  The pH of distilled water is about 7.0, and blood is about 7.35
  • The stronger an acid is, the lower the number on the pH scale.  A very strong acid like HCl may register a pH as low as 1-3, depending on its concentration. 
  • The stronger a base is, the higher the number on the pH scale.  A very strong acid like NaOH may register a pH as high as 11-13, depending on its concentration. 
  • STRONG ACIDS AND BASES CAN CAUSE BURNS AND DAMAGE TISSUES - BE CAREFUL WHEN USING!

Questions

Please answer the questions below.

How do you plan on changing the external environment of the system (your independent variable)?  

How do you plan on measuring the effect of your change to the system (your dependent variable)?

Don't forget: you should be taking TWO measurements!

Now that you have identified the cause-effect relationship you are testing, make a hypothesis about what you think will happen during the experiment. Remember that your hypothesis should be an if-then statement and should include some form of explanation.  

Here is an example hypothesis: 

If a shell-less egg is placed in distilled water, then the mass of the egg will increase because water moves across the cell membrane by diffusion. 

NOTE: You might not be able to give a full scientific explanation at this point, but you should be able to provide a reason why you think something will happen!

In the space below, provide a summary (or numbered list) of how you will conduct your investigation.  Make sure you are SPECIFIC in terms of units, time, etc. 

Please make sure to explain the exact method you are using to manipulate the control and the experimental group (how are you adding drops, what are doing to cup, how many drops, etc), how you are collecting data (again, anything you are specifically doing when you are conducting test), etc. 

Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.