what is the connection?. a conceptual problem… q = how do cells feed and excrete? a = via their...
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What Is The Connection?
A conceptual problem…
• Q = How do cells feed and excrete?
• A = Via their cell membranes
• So therefore, shouldn’t cells require MORE surface area?
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)
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
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
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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