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2. Ion channels that permit ions to pass between the interior of the cell and the extra-cellular medium are an important part of a living cell. There are multiple mechanisms that happen in an ion channel, but the simplest is that ions flow through the cell preferentially in one direction as a result of diffusion arising from a difference of ion concentrations on the inside and outside of the cell. L Cout As a first model of an ion channel, let's see how it would behave if the flux through the open channel were simply due to diffusion arising from a concentration difference. We'll model the open channel as a cylinder as shown in the figure at the left. Ас Fick's law for flow due to a concentration gradient is J = -D where D is the diffusion Ax constant and J has dimensions corresponding to number per unit area per unit time. 2.1 A typical ion channel radius is about 1 nm (nanometer), and the thickness of the cell membrane is about 7 nm. The concentration of Na+ ions inside a mammalian heart cell is about 0.6 ions/nm³, and in the fluid surrounding the cell is about 6.0 ions/nm³. The diffusion constant for ions is about 10° nm²/s (nanometers/second). If the channel were just an open cylinder, how many ions per second would flow through the channel and in which direction? 2.2 What is responsible for the flow of the ions through the channel in this model? A. The ions are attracted to the channel and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. B. The ions move randomly as a result of collisions with the fluid molecules and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. C. There are more ions in the high concentration region. Their collisions with each other drive the ions in all direction and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. D. The ions sense when the channel is open and explicitly move towards it. 2.3 Can this "diffusion constant, D" be the same constant as in the other Fick's law equation, (x²) = 2D At? Show whether they have the same dimensionality or not.

2. Ion channels that permit ions to pass between the interior of the cell and the extra-cellular medium are an important part of a living cell. There are multiple mechanisms that happen in an ion channel, but the simplest is that ions flow through the cell preferentially in one direction as a result of diffusion arising from a difference of ion concentrations on the inside and outside of the cell. L Cout As a first model of an ion channel, let's see how it would behave if the flux through the open channel were simply due to diffusion arising from a concentration difference. We'll model the open channel as a cylinder as shown in the figure at the left. Ас Fick's law for flow due to a concentration gradient is J = -D where D is the diffusion Ax constant and J has dimensions corresponding to number per unit area per unit time. 2.1 A typical ion channel radius is about 1 nm (nanometer), and the thickness of the cell membrane is about 7 nm. The concentration of Na+ ions inside a mammalian heart cell is about 0.6 ions/nm³, and in the fluid surrounding the cell is about 6.0 ions/nm³. The diffusion constant for ions is about 10° nm²/s (nanometers/second). If the channel were just an open cylinder, how many ions per second would flow through the channel and in which direction? 2.2 What is responsible for the flow of the ions through the channel in this model? A. The ions are attracted to the channel and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. B. The ions move randomly as a result of collisions with the fluid molecules and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. C. There are more ions in the high concentration region. Their collisions with each other drive the ions in all direction and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. D. The ions sense when the channel is open and explicitly move towards it. 2.3 Can this "diffusion constant, D" be the same constant as in the other Fick's law equation, (x²) = 2D At? Show whether they have the same dimensionality or not.

College Physics
College Physics
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ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
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2. Ion channels that permit ions to pass between the interior of the cell and the extra-cellular medium are an important part of a living cell. There are multiple mechanisms that happen in an ion channel, but the simplest is that ions flow through the cell preferentially in one direction as a result of diffusion arising from a difference of ion concentrations on the inside and outside of the cell. L Cout As a first model of an ion channel, let's see how it would behave if the flux through the open channel were simply due to diffusion arising from a concentration difference. We'll model the open channel as a cylinder as shown in the figure at the left. Ас Fick's law for flow due to a concentration gradient is J = -D where D is the diffusion Ax constant and J has dimensions corresponding to number per unit area per unit time. 2.1 A typical ion channel radius is about 1 nm (nanometer), and the thickness of the cell membrane is about 7 nm. The concentration of Na+ ions inside a mammalian heart cell is about 0.6 ions/nm³, and in the fluid surrounding the cell is about 6.0 ions/nm³. The diffusion constant for ions is about 10° nm²/s (nanometers/second). If the channel were just an open cylinder, how many ions per second would flow through the channel and in which direction? 2.2 What is responsible for the flow of the ions through the channel in this model? A. The ions are attracted to the channel and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. B. The ions move randomly as a result of collisions with the fluid molecules and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. C. There are more ions in the high concentration region. Their collisions with each other drive the ions in all direction and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. D. The ions sense when the channel is open and explicitly move towards it. 2.3 Can this "diffusion constant, D" be the same constant as in the other Fick's law equation, (x²) = 2D At? Show whether they have the same dimensionality or not.
Transcribed Image Text:2. Ion channels that permit ions to pass between the interior of the cell and the extra-cellular medium are an important part of a living cell. There are multiple mechanisms that happen in an ion channel, but the simplest is that ions flow through the cell preferentially in one direction as a result of diffusion arising from a difference of ion concentrations on the inside and outside of the cell. L Cout As a first model of an ion channel, let's see how it would behave if the flux through the open channel were simply due to diffusion arising from a concentration difference. We'll model the open channel as a cylinder as shown in the figure at the left. Ас Fick's law for flow due to a concentration gradient is J = -D where D is the diffusion Ax constant and J has dimensions corresponding to number per unit area per unit time. 2.1 A typical ion channel radius is about 1 nm (nanometer), and the thickness of the cell membrane is about 7 nm. The concentration of Na+ ions inside a mammalian heart cell is about 0.6 ions/nm³, and in the fluid surrounding the cell is about 6.0 ions/nm³. The diffusion constant for ions is about 10° nm²/s (nanometers/second). If the channel were just an open cylinder, how many ions per second would flow through the channel and in which direction? 2.2 What is responsible for the flow of the ions through the channel in this model? A. The ions are attracted to the channel and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. B. The ions move randomly as a result of collisions with the fluid molecules and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. C. There are more ions in the high concentration region. Their collisions with each other drive the ions in all direction and since there are more on one side than the other there is a net flow from the more dense concentration side to the less. D. The ions sense when the channel is open and explicitly move towards it. 2.3 Can this "diffusion constant, D" be the same constant as in the other Fick's law equation, (x²) = 2D At? Show whether they have the same dimensionality or not.
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