Decent exposure: Biology class hosts “Naked Egg” lab

Photos Courtesy of Kristin Bingham, biology department chair at SPC

The title of this lab may draw giggles from a seventh-grade sense of humor, but it’s not meant to. 

This week students used “naked eggs” to learn first-hand what osmosis means in zoology lab. The term “naked” here means “without shells”. 

According to Dr. Harriet Strickland, SPC biology instructor, osmosis is a process that happens when water molecules pass through a membrane from a less concentrated solution into a more concentrated one. The end result? Equal water concentrations on both sides of the membrane—not necessarily a “good thing” for a naked egg or a living cell. 

She says the whole concept of osmosis is hard for students to visualize.  So, she says, instead of just memorizing the concept on paper, she designed this lab to help students see how the process actually works.

“Using our common sense,” she says, “we all tend to want to end up with equal volumes of solution on both sides of a membrane.  We tend to overlook the concentration factor.”

Prior to this lab, Strickland says she soaked dozens of raw eggs in vinegar to dissolve their shells. Without the shells, the outside of the eggs are only left with clear, delicate membranes. That makes it easy for water to pass through the membranes, moving into or out of the raw eggs.  Strickland says that the “trick” to the osmosis process is that most other components of a solution cannot fit through the membranes—only the water makes it through to the “other side”. 

“In Biology, we strive to make abstract concepts more tangible for students using everyday materials,” says SPC Associate Professor and Chairperson of the Biology Department Kristin Bingham.  “When students can see with their eyes what happens to cells in response to a change in environment, they are more concretely able to process how that same change would happen within their own bodies.”

Students in this lab carefully weighed each “naked” egg before placing it in a bath of an everyday solution such as distilled water, iced coffee, Gatorade, apple juice, ocean water, or Levelland tap water.  They labelled each experiment to await results.

In the end, which liquid has the water concentration least like the inside of the raw eggs? Will the eggs shrink and shrivel up?  Or will they expand and maybe even explode due to the movement of water through their membranes? 

Results will show up in the next lab.

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