The outer membranes of cells are quite irregular at the submicron level, so the

Question

The outer membranes of cells are quite irregular at the submicron level, so the surface area of an apparently spherical cell differs from the value one would calculate from geometry. To determine the actual surface area of a cell membrane, electrophysiologists use intracellular electrodes to measure the membrane's capacitive reactance. They take advantage of the fact that the capacitance per unit area of all biological membranes is about 1.0*10^-6F/cm^2 . What is the surface area of a 20*10^-6m -diameter sphere? Give your answer in square centimeters.
The capacitive reactance of the outer membrane of a 20*10^6 -diameter cell is measured to be 6.4*10^6 ohmas at 1.0kHz . What is the surface area of the membrane, in cm^2 ? An important biological process is the release of neurotransmitters that are involved in chemical communication between nerve cells and muscles. This release occurs when intracellular vesicles containing the neurotransmitter chemical fuse with the outer cell membrane and release their contents. The vesicle's membrane becomes part of the cell's outer membrane, increasing the latter's area. As a result, the fusion of vesicles with the outer membrane can be detected by monitoring the outer membrane's capacitive reactance. Indeed, the fusion of a single vesicle can be resolved. What is the percentage increase in the capacitive reactance of the cell considered in part B when a single vesicle's membrane, a smooth sphere 0.10*10^-6m in diameter, fuses with the outer membrane of the cell?

Explanation / Answer

D = -1.3*10^-3 %

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