Cell Processes: Modeling Endocytosis: The Jelly Bean Problem

I just refer to this activity as modeling endocytosis, but you might not want to refer to it that way, as it may give too much away to your students.  

It comes from the Access Excellence collection and is named The Jelly Bean Problem.

In short, the students are trying to get a handful of candy into a plastic bag following these rules:

• The candy must enter through a solid part of the bag.
• The inside of the bag may not be directly open to the external environment.
• The candies entering the bag must remain clustered together.
• Students may work with their hands in the bag to act as the inside of a cell.
• The candy may be eaten only if it enters the bag "cell" under the specified conditions. 

Check out the original version for a nice illustration of how to accomplish this goal.

It's fun, candy is always an attention-getter, and it relates directly to cells.