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Modeling Limits to Cell Size Pre-Lab: Does Size Matter? Using the website http://learn.genetics.utah.edu/content/cells/scale/ Make to observations/reactions of the size comparisons between everyday object and some of the microscopic objects relevant to biology. 1. 2. Purpose: There are practical limitations as to the sizes, large and small, of living things. As organisms grow in surface area, interesting things happen to the inside. We will use cubes to compare the ratio of surface area to volume, as surface area increases. Hypothesis: As we increase the surface area of a cube, what will happen to the ratio of surface area to volume? Will it stay the same? Will surface area grow faster than volume? Will the volume grow faster than the surface area? Materials: Cube handout, scissors, tape Procedure: a. Use the provided handout to cut out each shape along the straight lines. b. Fold each shape along the dotted lines to form 3 cubes; tape to hold together in a three dimensional model. c. Calculate surface area ((length x width) x 6) and volume (length x width x height) for each and record in the data table below. d. Calculate ratio of surface area to volume and record in the data table. Data Table 1. Measurements of Cube Cell Models Cell Size in Units Area of One Face Surface Area Volume of Cube Cell (L x W) (L x W) x 6 (L x W x H) 1 3 5 Data Table 2. Ratios of Cube Cell Models Cell Size Units Surface Area-to-Volume Ratio 1 3 5 Analysis Questions: 1. How far from the center to the edge was the smallest cell? ____________ How far from the center to the edge was the largest cell? ________________ 2. Which measurement that you have calculated best represents how much cell membrane the cube models have? 3. The nucleus and cytoplasm and other organelles use oxygen and food while producing waste. Which measurement that you calculated best represents the cell content (the cytoplasm and all organelles on the inside)? 4. As the cell grows larger and increases in volume, will it need more or less cell membrane to survive? 5. Which cell size has the greatest Surface Area -to- Volume Ratio? 6. As the cell grows larger, does the Surface Area -to- Volume Ratio get larger, smaller, or remain the same? 7. Why can't cells survive when the Surface Area -to- Volume ratio becomes too small? 8. Which cell size has the greatest chance of survival? Which cell would be more efficient at moving materials in an out of the cell?