Lesson 3

Lesson Objectives...

• Plan and conduct an investigation in order to produce data to determine whether food molecules can travel from one side of a system to the other side separated by a solid structure with properties similar to the walls of the small intestine. 

• Argue from evidence to revise a model to show how the results of this investigation and graphs of different types of food molecules traveling through the small intestine explain how the structure of the walls impacts the function of the small intestine.

Resources for Lesson 3...

Investigating Dialysis Tubing...

Watch the video to observe and understand dialysis tubing.  Scientist and engineers have developed this special material that has very similar properties to those that make up the surface of the small intestine.

Why might we want to use this special material (dialysis tubing) to investigate our questions?

Plan Our Dialysis Tube Investigation...

Conducting Our Dialysis Tube Investigation...

Use the document to understand how our experiment is set up (Part 1) and when making prediction (Part 2).

Use the document to understand the use of iodine and Benedict's solution to indicate the evidence of food molecules.

Video of Dialysis Tube Investigation...

The first video shows the lab being set up and the second video show the analysis of the solutions for food molecules.

The Results...

Iodine is a chemical indicator for the food molecule starch.  If the brown color of iodine changes from brown to black, starch is present.

Benedict's Solution is a chemical indicator for the food molecule glucose.  If the blue color of Benedict's Solution changes from blue to another color, glucose is present.

Compare Molecular Representations of Glucose and Starch...

Compare the structure of a complex carbohydrate molecule (like starch) to a sugar molecule (like glucose).

What we figured out this lesson...

• The structure of the walls of the small intestine and dialysis tubing must have microscopic openings / gates in them that let small food molecules through but not large ones.

• Sugar molecules, such as glucose, are much smaller than molecules of complex carbohydrates, such as starch, but both are made up of the same types of atoms (carbon, hydrogen, and oxygen).