The following paragraph demonstrates some of the terms you learned in the osmosis and diffusion lab. Read over the paragraph and fill in the blanks with the appropriate term.
Cells interact with their environment by moving substances (water, gases, and salts) across cell membrane into and out of the cell. _____(a)_______ is the movement of molecules from a region of higher concentration to a region of lower concentration. Movement of molecules occurs due to ______(b)__________ energy (energy of motion). Diffusion will continue until molecules become evenly disturbed and a concentration gradient no longer exist. This is referred to as _____(c)___________. Several factors affect the rate of diffusion. Two examples studied in lab include ______(d)__________ and ______(e)________. ______(f)_________ is a method used to measure the diffusion of solute molecules through a semi-permeable membrane. The diffusion of water through a semi-permeable membrane is referred to as ______(g)__________. When the environment outside the cells has a lower concentration of dissolved molecules that inside the cell, the solution is said to be ______(h)___________, and water will move from the solution into the cell, thus causing the cell to ______(i)_________ and sometimes causing the cell to _______(j)_________(as is the case with animal cells in extremely dilute solutions). If the environment outside the cell has a higher concentration of dissolved molecules that inside the cell, the solution is said to be _____(k)___________. In this case, water will move out of the cell causing the cells to ______(l)__________. If the concentration of dissolved molecules are the same inside and outside the cell the solution is ____(m)_________ and no net movement of water occurs across the membrane.
Experiment 1: Mass and Diffusion Rate
Question: Using the graph, what is the relationship between mass and diffusion rate?
Experiment 2: Temperature and Diffusion Rate
Question: Using the graph, what is the relationship between temperature and diffusion rate?
Experiment 1.0: A dialysis bag containing 25% glucose and 25% starch is immersed into a beaker containing distilled water and Lugol's iodine solution. Using the Benedict's solution we obtained the following results. Note: The distilled water remained a pale yellow throughout the experiment.
A = Artificial cell incubated for 20 minutes
B= Tube 1 contains a sample of the distilled water (beaker A) and the Benedict's solution
Tube 2 contains a distilled water and the Benedict's solution
Answer the following questions concerning the experiment:
1. Which tube is considered the negative control?
2. I2KI reagent was added to the beaker to test for what macromolecule?
3. What color change occurs in the presence of this macromolecule?
4. Benedict's reagent is used to test for what macromolecule?
5. What color change occurs in the presence of this molecule?
6. According to the experimental results, which macromolecule diffuses through the dialysis bag?
7. Would you expect the solution inside the bag to change colors?
Experiment 2: A dialysis bag contains 10% glucose, 10% NaCL, 10% starch, and 10% protein is immersed in a beaker containing distilled water. Using the test for Silver Nitrate we obtained the following results.
B. 1 (left) 2 (right)
A= Artificial cell incubated for 20 minutes
B= Tube 1 contains a sample of distilled water (beaker A) and silver nitrate
Tube 2 contains distilled water and silver nitrate
Answer the questions concerning the experiment:
Red blood cells are permeable to water molecules. The diffusion of water is called osmosis. Given that the interior of the red blood cells has a salt concentration of 0.9% NaCL.
For each treatment answer the following questions:
ANSWERS TO THE REVIEW
Written by Jacqueline Jordan and pictures by Christopher Kodani and Barbara Foster. Clayton State University Morrow, GA Copyright 2002-Department of Natural Sciences, Clayton State University. Do not copy or use anything from these pages without written permission.