Introduction

We made a model of a cell to better understand how a selectively permeable cell membrane works relative to osmosis, much like the cell's balancing act with its environment. The other parts of the lab, the “sub-experiments” were given to show how the membranes react from a different perspective - from the perspective of a magnification of its microscopic environment.

I predict that the model of the cell would demonstrate how a selectively permeable cell membrane works. Since we were instructed to place some solutions (other than water) into the object to simulate a cell membrane, it is reasonable to infer that those solutions will be the solutes in the demonstration of osmosis.

The permeability of the cell membrane is important. If the cell membrane was always permeable to any type of molecule, the organelles within the cell would have to adapt rapidly to any threats and unplanned-intrusions. These adaptations may not be immediate, but rather, may take many generations to be put into full effect, e.g., the cells must reproduce and continue to copy and die off until a cell has developed an adaptation to the (originally threatening) molecules otherwise prevented from entrance by the membrane. It is also important in the sense that it allows various molecules into the cell. If the membrane did not allow the molecules that the cell requires to survive, there would be obvious problems, such as death. The process of limiting how much of a molecule is on one “side” (inside or outside) of the cell is noticeable in osmosis, the diffusion of water, or another solvent, across the cell membrane to an area of high solute concentration (and hence an area with a low solvent (such as water) concentration).

We made the dialysis bag to simulate a selectively permeable cell membrane. This demonstration is meant to develop our understanding of how a selectively permeable cell membrane works. Additionally, we mounted Elodea Leafs to examine the changes in the locations of the chloroplast and cell wall structure when the cells were exposed to non-distilled water. The tasks and procedures involved in this portion of the lab were meant to lead the participator to recognize the cellular-level effects on the chloroplast, cell walls, et cetera.

The dialysis bag is a suitable thing to use to serve as the "selectively permeable cell membrane" because it works similarly; given the solutions of starch, glucose (etc) to represent the molecules which would pass through the membrane, the dialysis bag also shows similar traits that the cell membrane would under similar conditions.

Like the membrane, the dialysis bag would allow osmosis to occur between its internals and within the external environment (the distilled water that the bag was floating in).

See the attached packet. The instructions are attached because I believe relevant data is mentioned on the page which is not on the other pages of the packet. The results of the solution-tests are..

Although not noticed by the human eye, many changes occur under some of the seemingly simplest changes of a cell's environment. For example, in this lab, we added salt water and recognized the movement of the chloroplast as they clumped together. This reaction to the salt water is not recognizable by the human eye, though that does not mean it does not take place.

Osmosis plays an important role in the balance of a cell and its environment as can be seen by the observations made while under the microscope, examining the changes as salt-water was added to the Elodea Leaf.