Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 50.0 m/s x 0.0020 s = 0.10 m). In the resting state, the outer surface of the axon wall is charged positively with K+ ions and the inne equal and opposite charge of negative organic ions, as shown in the figure below. Model the axon as a parallel-plate capacitor and take C = xc A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 2.0 x 1 radius r = 1.6 x 10¹ μm, and cell-wall dielectric constant x = 2.9. External fluid Positive charge layer { Negative { charge layer Axon wall membrane Internal fluid Axon radius r d @ (a) Calculate the positive charge on the outside of a 0.10-m piece of axon when it is not conducting an electric pulse. (Assume an initial potential difference of 7.0 x 10-² V.) 9.03E-10 How many K+ ions are on the outside of the axon assuming an initial potential difference of 7.0 x 10-² V? 5.639E9 ✓K+ ions Is this a large charge per unit area? Hint: Calculate the charge per unit area in terms of electronic charge e per angstrom squared (A2). An atom has a cross section of about 1 A² (1 A-10-10 m). (Compare to normal atomic spacing of one atom every few Å.) O Yes

Nerve cells in your body can be electrically stimulated; a large enough change in a membrane potential triggers a nerve impulse. Certain plants work the same way. A touch to mimosa pudica, the “sensitive plant,” causes the leaflets to fold inward and droop. We can trigger this response electrically as well. In one experiment, investigators placed electrodes on the thick tissue at the base of a leaf. The electrodes were 3.5 mm apart. When the electrodes were connected to a 47 μF capacitor charged to 1.5 V, this stimulated a response from the plant.a. Eventually, all the charge on the capacitor was transferred to the plant. How much charge was transferred?b. What was the approximate electric field between the electrodes?

Saccharomyces cerevisiae is a single-celled yeast that is often used as a model for eukaryotic cells, as it contains all of the important organelles of these cells. The genome of Saccharomyces cerevisiae, commonly known as brewer's yeast, has been completely mapped, making it suitable for genetic engineering experiments. The amount of electric charge on the cell walls plays a significant role in the interaction of these cells with their environment. To determine -9 the electric charge on yeast cells, which is a function of their size, the cells are often placed in electric fields and their motion in these fields is measured. In one such experiment, Saccharomyces cells of mass 3.00 x 10- 9 placed at rest in a uniform electric field of magnitude 10.0 N/C were measured to be traveling with a speed of 3.10 x 102 um/s after traversing a distance of 20.0 μm along the direction of the electric field. What was the magnitude and sign of the charge on this batch of yeast cells? (a) magnitude (in…

Saccharomyces cerevisiae is a single-celled yeast that is often used as a model for eukaryotic cells, as it contains all of the important organelles of these cells. The genome of Saccharomyces cerevisiae, commonly known as brewer's yeast, has been completely mapped, making it suitable for genetic engineering experiments. The amount of electric charge on the cell walls plays a significant role in the interaction of these cells with their environment. To determine the electric charge on yeast cells, which is a function of their size, the cells are often placed in electric fields and their motion in these fields is measured. In one such experiment, Saccharomyces cells of mass 3.00 x 109 g placed at rest in a uniform electric field of magnitude 10.0 N/C were measured to be traveling with a speed of 3.60 x 10² μm/s after traversing a distance of 16.0 μm along the direction of the electric field. What was the magnitude and sign of the charge on this batch of yeast cells? (a) magnitude (in C)…