In our Dual Credit Biology Labs, our students are studying the molecules of life – carbohydrates, lipids and proteins – and building an understanding of their importance in structure and function of cell membranes.

Additionally, they are studying the chemistry of water -its, properties,  interactions with other molecules and its movement through cell membranes – all important to sustaining life.  The lab highlighted the structure of a cell membrane with students viewing and then constructing their own phospholipid bi layer cell membrane model. 

The colorful “moving milk” activity help the students better understand surface tension and the action of detergents on lipids.  A dialysis tube,  filled with starch solution and place in an iodine solution, was used in another activity to simulate the selective permeability of a cell membrane – controlling what molecules are allowed in or out of the cell. 

Due to a color change of the starch solution (white to purple) the students could see that the small iodine molecules could pass through the membrane, but the lack of a color change in the iodine solution indicated that the starch molecules in the dialysis tube were too large to go through the membrane.