Life Science Class Summary 3/2/15

with Leigh Ann Yoder

Diffusion Discussion

At the beginning of class we immediately began our lab on Cell Membranes and Permeability. We began by observing a model cell I had set up 24 hours prior to our class. The cell membrane was represented by a sandwich bag, the interior of the cell was filled with a starch solution and the outer environment was iodine. Students first observed the chemical reaction that takes place when iodine mixes with starch. Then we examined our model cell together. We observed and discussed that the cell membrane was selectively permeable, allowing iodine to pass into the cell, but did not allow the starch to pass out. This was determined to be due to the membrane pore size. Students successfully identified that our model cell represented passive diffusion.

Students next set up Part II of our lab which tested the effects of concentration on diffusion. They soaked potato cubes in three different concentrations of iodine. After 30 minutes, students measured the distance of diffusion in the three potato cubes and were able to draw the conclusion that the greater the concentration of iodine, the greater the distance of diffusion. Students then applied their knowledge and were able to determine why sick people wear oxygen masks. Please ask your student to explain this.

While our potatoes were soaking we had time to discuss the results of our Egg-speriment as well as review key concepts covered in our weekly learning. We specifically focused on diffusion, osmosis, and active and passive transport.

Notes: Please bring goggles and cleaned jars next week. Also, if you have not already paid your supply fee please bring next week. Thank you.

Homework

Mandatory:
Read 2.1 and 2.2 (Photosynthesis and Respiration)
Complete the study guide for both 2.1 and 2.2

Optional:
Take Chapter 1 Test and bring for grading (highly recommended)
Online Activities pg. 46 and 52