Cell Growth Activity
WHY DON’T CELLS GROW INDEFINITELY?
Cell size is influenced by many different factors. The cell’s specific function is one of the main factors that determine cell’s size and shape. For example, the shape of a red blood cell is directly related to its ability to carry large amounts of oxygen. Other factors to consider are surface area, volume and mass of the cell, which all change as a cell grows. For example, think of filling a balloon with water. As water enters the balloon, the balloon gets stretched which changes the surface area, the balloon gets bigger, which changes the volume and the balloon gets heavier, which changes the mass. Of these factors, which one limits the overall size of a cell? In addition, how do these factors change in relationship to each other?
This activity is designed to consider the relationship between surface area, volume and mass as a cell grows. Before producing cell models to help consider these relationship, make a prediction about what happens to the surface area to volume ratio and the surface area to mass ratio as a cell grows.
Hypothesis:
Now, collect data to support or reject the above stated hypothesis. After the data has been collected, complete the analysis section.
Analysis:
1. Anything a cell takes in or lets out must pass through the plasma membrane. Which measurement best represents the plasma membrane?
2. The cell contents, including the cytoplasm and the organelles, use food and oxygen and produce waste. Which two measurements best represent the contents of your model?
3. As the cell grows larger and accumulates more contents, will it need more or less cell membrane to survive? Explain your answer.
4. As the cell grows larger, what happens to the surface area to volume ratio? Explain the relationship between these factors as the cell grows.
5. As the cell grows larger, what happens to the surface area to mass ratio? Explain the relationship between these factors as the cells grows.
6. How are the total surface area/volume ratio and the total surface area/mass ratio related to the cell survival?
7. Which size cell (small, medium or large) would have the greatest chance for survival and why?
8. Did the data support or reject the hypothesis?
Procedure:
1. Produce three cubes from the provided template. There should be a small, medium and large cube. These cubes will represent the different sizes that occur as a cell is growing.
2. Calculate the surface area of one face of each cube, using the following
equation: s X s. Place this information in the data table.
3. Calculate the total surface area of each cube, using the following equation: 6 X (s X s). Place this information in the data table.
4. Calculate the volume of each cube, using the following equation:
s X s X s. Place this information in the data table.
5. Determine the mass of each cube by filling the cube with bird seed and
weighing it on a balance.
6. Calculate the total surface area to volume ratio and the total surface area
to mass ratio. Place this information in the data table.
Small CubeS= 12.5 mm / Medium Cube
S=25 mm / Large Cube
S=50 mm
Area of One Face
Total Surface Area
Volume
Mass (Weight)
Total Surface Area/
Volume Ratio
Total Surface Area/
Mass Ratio