Remember the old salad dressing commercial tag-line "…because oil and vinegar don’t mix!" Water has that same love/hate relationship with many other molecules. Through this series of lessons, students will learn about the properties which make other molecules "love" or "hate" water. They will also begin to build a concept of how molecules derive their shapes when placed in water-based environments such as cellular cytoplasm. The packet is divided into several activities that are described below and are meant to be completed in the order indicated.
I. "Its All in the Shape" - Students use gumdrops and toothpicks to build three dimensional models of simple molecules like water, alcohol, etc. In this exercise students learn that even simple molecules have 3-dimensional shapes even though structural formulas appear to only have two.
II. "To Mix or Not to Mix" – In this lesson, students are provided with an opportunity to make selections, observations, conclusions, and form hypotheses regarding solution miscabilities ("mixabilities"). In the process, students discover what makes a molecule either "water-loving" or "water-hating".
III. Through a demonstration, students will observe the behavior of oil droplets in alcohol. For homework, they will carry out a set of calculations and make some conclusions based on their calculations and their observations from the oil/alcohol demonstration.
IV. As preparation for "As the Molecule Turns," students will use references to learn about five different proteins of their choosing. They will also classify several of the 20 amino acid side chains as either "water-loving" or "water-hating" based on the results of "To Mix or Not to Mix". "As the Molecule Turns" – It is often terribly difficult for students to visualize such things as molecular structure and activity. Technology has developed, however, to a point that CAD programs are now available that can help us "see" molecules in their bonding arrangements. In this activity, students will use a computer program to visualize proteins and to discover how the behavior of "water-loving" and "water-hating" molecules plays an important role in regard to protein shape.
Life Science, High School, Honors, or Advanced Placement Biology.
Three 45 minute in-class periods. Minimal teacher preparation time is required.
"It’s All in the Shape":
"To Mix or Not to Mix - That is the Question":
"As the Molecule Turns":
General Lab Supplies