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Cellular Diffusion Rates: Exploring Surface Area to Volume Ratios

This lab assesses how cell size impacts diffusion by measuring conductivity of solutions to determine rate of change. Students calculate surface area to volume ratios of agar cubes to understand the relationship better. Data collection involves immersing cubes in tap water and recording conductivity over time. The analysis includes graphing rates of diffusion against S.A. to Vol. ratios and answering related questions in a lab notebook.

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Cellular Diffusion Rates: Exploring Surface Area to Volume Ratios

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Presentation Transcript

  1. What Is The Connection?

  2. A conceptual problem… • Q = How do cells feed and excrete? • A = Via their cell membranes • So therefore, shouldn’t cells require MORE surface area?

  3. Lab: Assessing the Rate of Cellular Diffusion v. Differing Surface Area to Volume Ratios • Purpose: To determine how the size of a cell is related to its ability to perform diffusion • Method: Measurement of conductivity of the solution. The greater the rate of diffusion, the greater the rate of change in conductivity (as measured in µS/cm/sec)

  4. Calculating S.A.: Vol Ratios • From block of sodium-infused agar, cut 3 2x2x2 blocks • Cut 2nd block into eight cubes • Cut 3rd block into 64 cubes • Calculate cumulative S.A.: Vol. ratios for each set of cubes

  5. Collecting the data • Place the first 2cm3 cube into 300 mL of tap water • Immerse the conductivity probe into the tap water bath • Collect data, while STIRRING CONSTANTLY for 300 seconds • Determine the slope in µS/cm/sec

  6. Processing/Interpreting The Data • Graph the rate (y-axis) vs. ratio of S.A.: Vol. (x-axis) • Answer the analysis questions in your lab notebook

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