Concept explainers
The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. Measurements with microelectrodes have shown that a 0.30-nm-diameter potassium ion (K+) channel carries a current of 1.8 pA. How many potassium ions pass through if the ion channel opens for 1.0 ms?
Want to see the full answer?
Check out a sample textbook solutionChapter 22 Solutions
College Physics: A Strategic Approach (3rd Edition)
Additional Science Textbook Solutions
Essential University Physics: Volume 2 (3rd Edition)
Conceptual Integrated Science
Essential University Physics: Volume 1 (3rd Edition)
Tutorials in Introductory Physics
University Physics with Modern Physics (14th Edition)
Physics for Scientists and Engineers with Modern Physics
- The portion of a nerve cell thatconducts signals is called an axon. Many of the electrical properties ofaxons are governed by ion channels, which are protein molecules thatspan the axon’s cell membrane. When open, each ion channel has apore that is filled with fluid of low resistivity and connects the interiorof the cell electrically to the medium outside the cell. In contrast, thelipid-rich cell membrane in which ion channels reside has very highresistivity. Assume that a typical open ion channel spanning an axon’s membrane has a resistance of 1 * 10^11 Ω. We can model this ion channel, with its pore, as a 12-nm-long cylinder of radius 0.3 nm. What is the resistivity of the fluid in the pore? (a) 10 Ω . m; (b) 6 Ω . m; (c) 2 Ω . m; (d) 1 Ω . m.arrow_forwardTwo resistors are wired in series with a 123 V battery. The first resistor has a resistance of 6 k and the second resistor has a resistance of 1 kQ. What is the current in amperes that is leaving the positive terminal of the battery?arrow_forwardA single ion channel is selectively permeable to K* and has a resistance of 2.40 G2. During an experiment, the channel is open for approximately 1.80 ms while the voltage across the channel is maintained at +80.5 mV with a patch clamp. How many ions, N, travel through the channel? N = K+ ionsarrow_forward
- As discussed in the chapter, a thermistor is a device whose resistance varies with temperature. At 20°C a thermistor’s resistance is 10.0 kΩ. When connected to a 1.2 V battery, the current through the thermistor increases by 30 μA as the temperature increases to 30°C. What is the thermistor’s resistance at this higher temperature?arrow_forwardplease helparrow_forwardIt turns out that humans are only harmed by current, not voltage, to the point where even 0.2 amps is almost certainly lethal. Yet for some reason we always see signs for “Danger: High Voltage”, even though voltage literally cannot hurt you. Why should you still stay away from high voltage objects, and does that mean you should worry about all objects that can supply voltage? It might be helpful to know that a dry human body has about 100,000 ohms of resistance, and we can’t feel current below 0.001 Amps.arrow_forward
- One hundred meters of a certain type of wire has a resistance of 7.2 Q. What is the resistance of 2.5 m of this wire? 0.30 2 0.18 Q 3.0 2 1.8 Q 18 Qarrow_forwardConsider the model of the axon as a capacitor from Figure P18.43. (a) How much energy doesit take to restore the inner wall of the axon to -7.0 x 10-2 V,starting from +3.0 x 10-2 V? (b) Find the average current inthe axon wall during this process.arrow_forwardA battery with an EMF of 12 V and an internal resistance of 1 2 is used to charge a battery with an EMF of 10 V and an internal resistance of 1 Q. The current in the circuit is: O 1A 4 A O 2 A O 0.5arrow_forward
- A water heater that is connected across the terminals of a 15.0 V power supply is able to heat 250 ml of water from room temperature of 25°C to boiling point in 45.0 secs. What is the resistance of the heater? The density of water is 1,000 kg/m2 and the specific heat capacity of water is 4,200 J/kg/°Carrow_forwardA Palduma water heater heats 1 liter (1000 cm?) of water from 19°C to 99°C in 10 minutes when 110 V is applied.What is the resistance of this heater?arrow_forwardAssume 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 %D resting state, the outer surface of the axon wall is charged positively with Kt ions and the inner wall has an 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 = KƐ A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell -8 wall thickness d = 1.5 x 10 m, axon radius r = 2.0 x 10- um, and cell-wall dielectric constant K = 2.9. External fluid + Positive charge layer Axon wall membrane d Negative charge layer Internal fluid Axon radius = r (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.) 1.035E-9 Your response differs from the correct answer by more than 10%.…arrow_forward
- College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningUniversity Physics (14th Edition)PhysicsISBN:9780133969290Author:Hugh D. Young, Roger A. FreedmanPublisher:PEARSONIntroduction To Quantum MechanicsPhysicsISBN:9781107189638Author:Griffiths, David J., Schroeter, Darrell F.Publisher:Cambridge University Press
- Physics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningLecture- Tutorials for Introductory AstronomyPhysicsISBN:9780321820464Author:Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina BrissendenPublisher:Addison-WesleyCollege Physics: A Strategic Approach (4th Editio...PhysicsISBN:9780134609034Author:Randall D. Knight (Professor Emeritus), Brian Jones, Stuart FieldPublisher:PEARSON