Name:______Period:______

Why don’t cells grow indefinitely?

Background:

Many cells grow until they reach a certain size and then divide. Why don’t cells grow indefinitely, until they become the size of basketballs? What problems arise when a cell grows larger? Why does a cell divide into two smaller cells when it reaches a certain size? These are all questions that scientists have attempted to resolve.

Cell division is a necessary part of life of any multi-cellular organism and allows for growth, repair, and formation of cells for reproduction. Growth of an organism occurs mainly by an increase in the number of cells rather than by the enlargement of individual cells. This process seems to be controlled by simple physical laws.

Problem:

What is the relationship among surface area, volume, and the mass of a cell?

Hypothesis:

Develop a hypothesis that predicts what will happen to the surface area-to-volume ratio and the surface area-to-mass ratios as a cell grows larger.

______

Procedure:

  1. Examine table 1. Next to the row marked formulas write in the mathematical formulas that can be used to calculate the value described in the heading of each column. Use “s” as the length of one side of your model. Once you have written in the formulas, let your teacher check them before you continue the investigation.
  2. Use your formulas to calculate values (except for the last column) for each of the three cell models. Record your values in Table 1.
  3. Obtain three different cells of different sizes and fill each cell with sand.
  4. Determine the mass of each sand-filled model cell by using a scale. Record the masses in the last column of Table 1.
  5. Calculate the ratio of total surface area-to-volume for each model cell. To do this, divide the cell’s total surface area by its volume. Place your answers in Table 2.
  6. Calculate the ratio of total surface area to mass for each model cell. To do this, divide the cell’s total surface area by its mass. Place your answers in Table 2.

Data:

Measurement of Cell Models
Formulas
Cell Size (Length of 1 side) / Area of one face (square units) / Total surface area of cell (Square units) / Volume of cell (cubic units) / Distance from center to edge (units) / Mass of cell (grams)
1
2
4
Ratios of Cell Model Measurements
Cell Size (Length of 1 side) / Total surface area / Volume / Total surface area / Mass
1
2
4

Conclusion 2-3 paragraphs:

Write a conclusion based on the results that you obtained from this lab. Answer the problem of the lab, state if your hypothesis was correct or not and why, describe the experiment, explain what you observed, and what changes would you make. Provide and example that would apply to the real world.