# Analyze the following cells units not to scale and

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Analyze the following cells (units not to scale), and determine the following… Cell 1 (spherical) where the radius is 3 mm Cell 2 (flat and rectangular) where the height is 0.5mm, length is 4mm, width is 2mm A) What is the surface area to volume ratio of both cells? How to calculate Surface Area? Surface area How to calculate Volume? Volume Surface area to Volume Ratio Cell 1 = 4 π r 2 4 π (3) 2 = 113 mm 2 4/3 π r 3 4/3 π (3) 3 = 113mm 3 133/133 = 1:1 Cell 2 = Σ a 16 + 4 + 2 = 22 mm 2 L x W x H 0.5 x 2 x4 = 4 mm 3 22:4 = 11:2 B) Conclusion: Compare the ratios and explain why one cell would be more efficient than another. As a cell increases in size, the volume grows at a faster rate than the surface area. As cells increase in volume, the relative surface area decreases and demand for material resources increases. These limitations restrict cell size. When the cell is too big, transport throughout the cell is over a longer distance. This means that it takes longer for nutrients to diffuse to where they are needed in the cell. In addition it takes longer to remove wastes. If a cell gets too big, the cell will have very little surface area compared to its volume to allow enough materials in and out of the cell. C) Are you made of lots of large cells or lots of small cells? Why? How do you actually grow in height? Made of small cells. They have a high surface area to volume ratio (see above) You grow in height by making MORE cells. While cells will grow in size, they will reach a limit of efficiency, and then perform mitosis. 2) Water potential in potato cells was determined in the following manner. The initial masses of six groups of potato cores were measured. The potato cores were placed in sucrose solutions of various molarities. The masses of the cores were measured again after 24 hours. Percent changes in mass were calculated. The results are shown below. Molarity of Sucrose in Beaker Percent Change in Mass 0.0 M 18.0 0.2 5.0 0.4 -8.0 0.6 -16.0 0.8 -23.5 1.0 -24.0

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Graph these data to the right of the table. From your graph, label where the cells were hypotonic and the solution was hypertonic, and vice versa. Determine the apparent molar concentration (osmolarity) of the potato core cells. Osmolarity = ~0.275M cell and solution are isotonic Above ~0.275M cells are hypotonic while the solution is hypertonic (as cells are gaining mass = water is moving in) Under ~0.275M cells are hypertonic and the solution is hypotonic (as cells are losing mass = water is moving out) Looking at the water potential equation, When Solute potential goes down (gets more negative), water potential DECREASES When Pressure potential goes down (gets smaller), water potential DECREASES When would the pressure in a cell rise? (Under what conditions?) Why can only walled cells such as bacteria, fungi and plant cells generate turgor pressure, whereas animal cells cannot?
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