Time to move 10 microns (typical size of animal cell) Object radius (nm) D(cm^2/

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Time to move 10 microns (typical size of animal cell)
Object radius (nm) D(cm^2/s) time (sec) oxygen 0.2 2*10-5 0.02 sucrose 0.5 5*10-6 0.13 insulin 1.4 1.6*10-8 0.3 hemoglobin 2.5 7*10-7 0.2 HIV 100 2.2*10-10 23 bead 250 8.9*10-9 56 bacteria 750 1.8*10-10 170
1b. What would be the appropriate units for the diffusion coefficient in this example? (2). Cm^2/s
1c. What would be another set of units that might also apply to diffusion coefficients? m^2/s
2. Cell Surface to Volume issues – this question asks students to become familiar with basic formulas used to calculate surface area and volume, and to understand how much surface area and volume change when the diameter of a cell (or organism) gets larger. It also gives practice in understanding the (confusing) concept of surface area to volume ratios. Finally, an important example of biological compensation for such matters is presented.

Time to move 10 microns (typical size of animal cell)
Object radius (nm) D(cm^2/s) time (sec) oxygen 0.2 2*10-5 0.02 sucrose 0.5 5*10-6 0.13 insulin 1.4 1.6*10-8 0.3 hemoglobin 2.5 7*10-7 0.2 HIV 100 2.2*10-10 23 bead 250 8.9*10-9 56 bacteria 750 1.8*10-10 170
1b. What would be the appropriate units for the diffusion coefficient in this example? (2). Cm^2/s
1c. What would be another set of units that might also apply to diffusion coefficients? m^2/s
2. Cell Surface to Volume issues – this question asks students to become familiar with basic formulas used to calculate surface area and volume, and to understand how much surface area and volume change when the diameter of a cell (or organism) gets larger. It also gives practice in understanding the (confusing) concept of surface area to volume ratios. Finally, an important example of biological compensation for such matters is presented.

Time to move 10 microns (typical size of animal cell)
Object radius (nm) D(cm^2/s) time (sec) oxygen 0.2 2*10-5 0.02 sucrose 0.5 5*10-6 0.13 insulin 1.4 1.6*10-8 0.3 hemoglobin 2.5 7*10-7 0.2 HIV 100 2.2*10-10 23 bead 250 8.9*10-9 56 bacteria 750 1.8*10-10 170
1b. What would be the appropriate units for the diffusion coefficient in this example? (2). Cm^2/s
1c. What would be another set of units that might also apply to diffusion coefficients? m^2/s
2. Cell Surface to Volume issues – this question asks students to become familiar with basic formulas used to calculate surface area and volume, and to understand how much surface area and volume change when the diameter of a cell (or organism) gets larger. It also gives practice in understanding the (confusing) concept of surface area to volume ratios. Finally, an important example of biological compensation for such matters is presented.

Explanation / Answer

1b) Since the radius of molecules here are expressed in CGS units therefore the unit for diffusion coefficient will be cm2/sec. Diffusion coefficient is the property of molecule.

1c) m2/sec can also be taken as unit of diffusion coefficient.It is the SI unit.

2)Cell surface to volume ratio is the surface area of cell divided by the volume of cell. Since cell is considered a sphere so it's surface area is 4r2nd volume is 4/3r3.Now this tells that cell surface to volume ratio is inversely proportional to radius of cell meaning that is radius is made 2 times the surface area to volume ratio decreases by half. The concept of cell surface to volume ratio is used to tell whether the cell will divide or not. Every cell has to maintain a constant SA to volume ratio. An increase in this ratio causes cell to divide.

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