Potato Cells Lab Report

Introduction

Potato cores are made of countless cells. A semi-permeable layer called the cell membrane surrounds each potato cell. The cell membrane acts as a barrier between the cytoplasm and its environment. It also gives the cell its structure. The reason why the cell membrane is semi-permeable is because it is mainly composed of a phospholipid bilayer that only allows non-polar and small molecules to pass through it. Fortunately, the cell membrane also contains many transport proteins that allow charged and larger molecules such as water to move into the cell. Other proteins in the cell membrane include glycoprotein and enzymes which are involved in cellular functions such as recognition of other cells and chemical messaging. Another component of the cell

membrane is cholesterol chains in the bilayer which keep the phospholipids from moving too far apart in warmer temperatures, and too close together in lower temperatures.
Some of the cell membrane’s transport proteins use facilitated diffusion to effortlessly move molecules into the cell, while others use active transport and energy to move molecules against their concentration gradient. In addition to transport proteins, the processes of phagocytosis, pinocytosis, and receptor-mediated endocytosis also move substances into the cell and exocytosis moves substances out of the cell. Osmosis occurs when water diffuses across a membrane. Because of water’s natural tendency to move from hypotonic (less concentrated) to hypertonic (more concentrated) solutions, cells must use the process of osmoregulation to avoid bursting due to excessive gain of water, and shriveling due to excessive loss of water.
Results
Concentration of Solution
Initial Mass (grams)
Final Mass (grams)
Mass Increase(+) or Decrease(-)
% Change in Mass of Potato (Final Mass-Initial Mass)Initial Mass100
Distilled Water
2.0
2.5
+
(2.5-2.0)2.0100=25
0.2 M sucrose
1.4
1.2
-
-14.3
0.4 M sucrose
1.4
1.0
-
-28.6
0.6 M sucrose
1.8
1.1
-
-38.9
0.8 M sucrose
1.3
0.8
-
-38.5
1.0 M sucrose
1.8
0.9
-
-50
(See last page for graph)
Discussion
The pattern observed in the graph shows that as the sucrose concentration of the solution increases, the mass of the potato core decreases. This means that the potato core lost more water as the solution became more concentrated because water moves down its concentration gradient until equilibrium is achieved. The potato core placed in 0M solution (distilled water) had a 25% increase in mass. This is because the solution was hypotonic to the potato so water diffused into its cells thus causing its mass to increase. The potato placed in 0.2M solution had a 14.3% decrease in mass. This is because the solution was hypertonic to the potato so the net movement of water was from the potato to the solution which then caused the potato’s mass to decrease. In 0.4M solution, the potato core had a 28.6% decrease in mass. This is because the solution was hypertonic to the potato core which allowed it to draw water molecules out of the potato cells and reduce the potato’s mass. In 0.6M solution, the potato had a 38.9% decrease in mass. This means that this solution was more hypertonic to the potato than 0.4M solution was because the potato core in 0.6M solution had a larger percent of decrease in mass, thus meaning more water moved out of this potato core. The potato had a 50% decrease in mass after being placed in 1.0M solution. This means that this solution was the most hypertonic in relation to the potato core because more water molecules moved out of the potato in this solution than any of the other ones, thus causing the mass of the potato in this solution to have the greatest percent of decrease.
Conclusion
According to the graph, the sucrose concentration of the potato is around 0.15M because that is where the sucrose concentration of the solution does not change the potato’s mass.

This means that in 0.15M solution, the cytoplasm of the potato cells are isotonic to the solution so the net movement of water between the two is equivalent. One possible source of error in this lab is that I did not pour the correct solution into each cup at first so my partner and I had to dump them out and restart. However, each cup already had a potato core in it at the time of the incident so the potato cells might have gained or lost some water before they were placed in the correct solution and this would have affected their changes in mass. Also, since the cups were stored next to a window during the lab, they were exposed to sunlight which could have caused some of the water in the solutions to evaporate. With less solvent, the solutions became more concentrated and hypertonic which would have caused larger decreases in the potato cores’ mass. One way to build off of this lab in the future is by replacing sucrose with salt or a different solute in the solutions and then comparing the effects on the potatoes’

masses.