What are the dependent and independent variables?

What are the Independent, Dependent, and Constant Variables and control group?

• A company that makes nutritional products is developing a new type of protein drink for athletes. A scientist at the company is studying the pH at which a digestive enzyme breaks down the diff. proteins in the drink. The scientist uses the following exp. procedure: - 5 test tubes each contain 2 mL of protein drink -5 diff solutions contain the digestive enzyme, but each solution has a diff pH: 1.5, 2.0, 2.5, 3.0, and 3.5. One enzyme solution is added to each test tube of protein drink. -protein levels are measured in each of the five test tubes. Identify: Independent Variables - Dependent Variables - Constant Variables (2-3) - Control Group (if there isn’t one what would it be) -

• Answer:

  Independent variables are variables that the person doing the experiment changes: in this case it is the different pH's of enzyme solution added. Dependent variables are variables that you measure as the result: in this case it's the protein levels measured in each tube, after the enzyme has done its work. Constant variables do not change during the experiment, this ensures that only the variable you're changing (independent) can affect the final result (dependent): in this case constant variables are -each test tube has 2ml of drink -the concentration of digestive enzyme is constant -temperature at which the experiment is conducted is kept the same, since enzymes are affected by it -the length of time that you allow the enzyme to do its function before you purify and measure the result A control group is a separate test you prepare to show that only the variable you change affects the result. To set up a control you could add a volume of acidic solution without the enzymes to a 6th test tube with 2ml protein drink. This would show that in all the tests it's not the acid that breaks down the drink, but the enzyme which digests it. If you're asked to plot a graph of the results, the independent variable values will go on the bottom x-axis running horizontally. The dependent values will go on the vertical y-axis. Hope this helps