3. Living cells "pump" singly ionized sodium ions, Na+, from the inside of the cell to the outside across the membrane potential AVmembrane Vin - Vout= -70 mV. It is called pumping because work must be done to move a positive ion from the negative inside of the cell to the positive outside, and it must go on continuously because sodium ions "leak" back through the cell wall by diffusion. a. How much work must be done to move one sodium ion from the inside of the cell to the outside? b. At rest, the human body uses energy at the rate of approximately 100 W to maintain basic metabolic functions. It has been estimated that 20% of this energy is used to operate the sodium pumps of the body. Estimate to one significant figure the number of sodium ions pumped per second.

3. Living cells "pump" singly ionized sodium ions, Na+, from the inside of the cell to the outside across the membrane potential AVmembrane Vin - Vout= -70 mV. It is called pumping because work must be done to move a positive ion from the negative inside of the cell to the positive outside, and it must go on continuously because sodium ions "leak" back through the cell wall by diffusion. a. How much work must be done to move one sodium ion from the inside of the cell to the outside? b. At rest, the human body uses energy at the rate of approximately 100 W to maintain basic metabolic functions. It has been estimated that 20% of this energy is used to operate the sodium pumps of the body. Estimate to one significant figure the number of sodium ions pumped per second.

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter7: Work, Energy, And Energy Resources

Section: Chapter Questions

Problem 40PE: (a) What is the available energy content, in joules, of a battery that operates a 2.00-W electric...

See similar textbooks

Similar questions

3 Nernst Potential A cell memberane is selectively permeable: some ions can flow through it, and others cannot. When ions diffuse acros the membrane, the difference in concentration creates an electric potential difference and an electric field. The difference in concentration of potassium ions inside and outside of the cell is the main contribution to the "resting potential" of a сross neuron. The Nernst potential is the potential difference across a cell membrane due to the diffusion of ions through it: kgT In AV = Ze Co kg = 1.38 x 10-23 J/K is Boltzmann's constant, T is the temperature in degrees kelvin (K), e is the proton charge, Z is the ionic charge, c, is the molar concentration inside the membrane, and c, is the molar concentration outside the membrane. For a singly ionized molecule – like sodium (Na*) or potassium (K+) ions – we have Z = 1. (a) Suppose that the extracellular fluid of a cell – the fluid outside the cell memberane – has a potassium ion con- centration of…
Living cells "pump" singly ionized sodium ions, Na", from the inside of the cell to the outside to maintain a membrane potential AV membrane = Vin - Vout - 70 mV. It is called pumping because work must be done to move a positive ion from the negative inside of the cell to the positive outside, and it must go on continuously because sodium ions "leak" back through the cell wall by diffusion. a. How much work must be done to move one sodium ion from the inside of the cell to the outside? b. At rest, the human body uses energy at the rate of approxi- mately 100 W to maintain basic metabolic functions. It has been estimated that 20% of this energy is used to operate the sodium pumps of the body. Estimate-to one significant figure the number of sodium ions pumped per second.
Item 13 Cell Membranes and Dielectrics Many cells in the body have a cell membrane whose inner and outer surfaces carry opposite charges, just like the plates of a parallel-plate capacitor. Suppose a typical cell membrane has a thickness of 8.5x109 m, and its inner and outer surfaces carry charge densities of -6.4×10-4 C/m² and +6.4×10-4 C/m², respectively. In addition, assume that the material in the cell membrane has a dielectric constant of 5.4. Part A Find the direction of the electric field within the cell membrane. into the cell O out of the cell Submit Part B E = Find the magnitude of the electric field within the cell membrane. Express your answer using two significant figures. —| ΑΣΦ Submit Part C Request Answer |AV| = Submit Request Answer Calculate the potential difference between the inner and outer walls of the membrane. Express your answer using two significant figures. 17 ΑΣΦ # ? Request Answer N/C ? mV
To measure signal propagation in a nerve in the arm, the nerve is triggered near the armpit. The peak of the action potential is measured at the elbow and then, 4.0 ms later, 24 cm away from the elbow at the wrist.a. What is the speed of propagation along this nerve?b. A determination of the speed made by measuring the time between the application of a stimulus at the armpit and the peak of an action potential at the elbow or the wrist would be inaccurate. Explain the problem with this approach, and why the noted technique is preferable.
A nerve cell is shaped like a cylinder. The membrane wall of the cylinder has a +0.07-V potential difference from the inside to the outside of the wall. To help maintain this potential difference, sodium ions are pumped from inside the cell to the outside. For a typical cell, 10^9 ions are pumped each second. a. Determine the change in chemical energy each second required to produce this increase in electric potential energy. b. If there are roughly 7×10^11 of these cells in the body, how much chemical energy is used in pumping sodium ions each second? c. Estimate the fraction of a person's metabolic rate used to pump these ions. Assume the metabolic rate to be 100 W.
If you examine your smartphone battery, you will likely see two numbers: the battery's "capacity" labeled in mAh (milliamps x hours or milliamp-hours), and the battery's voltage or potential difference in V (volts). 1. What physical quantity is the battery's "capacity" measuring? Explain how you can tell. This answer has not been graded yet. 2. Suppose your phone's battery has a capacity of 2500 mAh and a potential difference of 3.7 V. What is the amount of charge, in C (coulombs), that is stored in your smartphone battery when it's fully charged? Charge = 3. Smartphone chargers are usually labeled with their current output in A (amps). Suppose your charger delivers a current of 1.1 A. If your phone's battery is completely drained, how long will it take to fully charge the battery using your charger? Charging time = hours 4. Smartphones are advertised with a certain amount of "talk time", i.e., how long the phone's battery will last if you are making a call. If your phone is advertised…
An unmyelinated segment of the axon has a radius of r-2 um and a length of L=5 cm. what is its membrane capacitance (Farad) ?. (The capacitance per unit area, C = 0.01 F/m?). A. 0.00000000628 B. 0.00000002512 C. 0.00000001884 D. 0.00000001256 E. None
PROBLEM NUMBER 2 Using the characteristics of Fig. determine I, for the following levels of VGs (with VDS > Vp): a. VGS = 0V. b. VGS = -1 V. c. VGS = -1.5 V. d. VGS = -1.8 V. e. VGS = -4 V. f. Vas= -6 V. IDSS 8 7 5 4 3 2 1 ID (mA) Ohmic Region | Locus of pinch-off values Saturation Region 15 10 Vp (for VGS = 0 V) 15 VGS = 0 V 20 VGS =-1 V VGS=-2 V VGS=-3 V VGS=-4V=VP VDS (V) 25
Rank the potential energies of the four systems of particles shown in Figure CQ16.4 from largest to smallest. Include equalities if appropriate. Figure CQ16.4
(a) What is the available energy content, in joules, of a battery that operates a 2.00-W electric clock for 18 months? (b) How long can a battery that can supply 8.00104 J run a pocket calculator that consumes energy at the rate of 1.00103 ?
Try to complete Table P26.4 from memory. If you must look back in this chapter or other chapters for information, note the page number, figure number, or equation number that helped you. TABLE P26.4
1. When air enters the insulated duct depicted in the following figure, it is at 65 °F and 1.2 atm of pressure; when it leaves, it is at 147 °F and just under 1.2 atm of pressure. The resistor receives 0.2 kW of electricity at a time. One can disregard the impacts of kinetic and potential energy. When operating in the steady state condition, a. Calculate the kW-based exergetic destruction rate. b. Design and assess an energy efficiency rating for the heater. Air 1.2 atm 65 °F wwwwwwwwwww Wev = -0.2 kW Insulation 147 °F