Place all answers into notebook

Investigating the Limits of Cell Growth

Pre-Lab Discussion:

In multicellular organisms, growth is accomplished by the production of more cells by cell division. Cell division will occur only when the cells have reached a size large enough to ensure that the resulting daughter cells will have all the necessary materials and structures for survival.

The rate of exchange of materials entering (food, oxygen, and water) and leaving (waste products) the cell through the cell membrane is determined by the cell’s surface area. And the rate at which these materials are used within the cell depends upon the cell’s volume, or the amount of space within the cell. A number of factors, such as the reduction of food and changes in temperature, can cause cells to stop growing and dividing.

In this investigation, you will observe on factor that limits cells growth.

Causal Question:

IV:

DV:

Hypothesis:

Materials List:

  • Plastic spoon
  • 3 gelatin blocks (1cm, 2cm and 3 cm)
  • Paper towel
  • plastic knife
  • Metric ruler
  • Food coloring
  • Water

Procedure:

  1. Using metric ruler measure and cut each gelatin block to the appropriate size (1cm block, 2cm block, 3 cm block).
  2. Place thegelatin blocks into the cup and add water so that the 3 blocks are submerged.
  3. Allow gelatin block to sit in the water solution for 15 minutes.
  4. While the blocks are soaking, use the formulas given below to determine the surface area, volume, and surface-area-to-volume ratio for each block. Record this information in Data Table #1

Surface are = number of surfaces x length x width

Volume = length x width x height

Surface-area-to-volume ratio = surface area

volume

  1. After 15 minutes, remove the blocks with the plastic spoon. Place them on the paper towel and blot them dry.
  1. Cut each block in half with the knife. Using the metric ruler, measure the distance in millimeters the color has diffused into each block. Then measure the distance from the end of the color to the center of the cube. Record these measurements in the appropriate places in Data Table 2.

Results:

Data Table 1

Cube Size / Surface Area
(cm2) / Volume
(cm3) / Surface-area-to-volume Ratio
3cm
2cm
1cm

Data Table 2

Cube Size / Distance color has diffused into Block (mm) / Distance from End of color to Block’s center (mm)
3cm
2cm
1cm

Questions to answer

  1. Which block has the greatest surface area?
  2. Which block has the greatest surface-area-to-volume ratio?
  3. In which block did the color diffuse the most? Explain your answer.
  4. If the blocks were actual cells, which would be the most efficient in terms of permitting materials to enter and leave the cells?
  5. Based on this investigation, what one factor may limit the growth of an individual cell?
  6. What happens to the surface-area-to-volume ratio of a cell as it grows?
  7. Propose a hypothesis that explains why the growth of a cell decreases as its size increases.