Question

5. Cells of the brain and heart, along with those in much of the body, need to transport sodium, potassium, and chlorine ions in and out to operate. Sometimes this occurs against the electric field gradient (ie. moving a positive charge from low to high potential). This is performed by active ion pumps on the selectively permeable cell membrane and requires energy. Consider the case where the inside of a cell is at -70 mV relative to the extracellular environment. A Na–K pump is required to move a Na+ ion out of the cell. Estimate the energy required. Repeat for a K+ ion. (20 marks) Cell interior Na+ 15 mM K+ 150 mM -70 mV Cl- 10 mM A- 100 mM Na+ 150 mM A- 0.2 mM K+ 5 mM Cl- 120 mM Cell exterior Cell exterior Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ Diffusion Na+ Diffusion Na+-K+ pump Plasma membrane Cell interior

          5. Cells of the brain and heart, along with those in much of the body, need to transport sodium, potassium, and chlorine ions in and out to operate. Sometimes this occurs against the electric field gradient (ie. moving a positive charge from low to high potential). This is performed by active ion pumps on the selectively permeable cell membrane and requires energy.

Consider the case where the inside of a cell is at -70 mV relative to the extracellular environment. A Na–K pump is required to move a Na+ ion out of the cell. Estimate the energy required. Repeat for a K+ ion. (20 marks)

Cell interior
Na+ 15 mM
K+ 150 mM
-70 mV
Cl- 10 mM
A- 100 mM
Na+ 150 mM
A- 0.2 mM
K+ 5 mM
Cl- 120 mM
Cell exterior
Cell exterior
Na+ Na+ Na+
Na+ Na+ Na+
K+ K+
K+ K+ K+
Diffusion
Na+ Diffusion
Na+-K+ pump
Plasma membrane
Cell interior

5. Cells of the brain and heart, along with those in much of the body, need to transport sodium, potassium, and chlorine ions in and out to operate. Sometimes this occurs against the electric field gradient (ie. moving a positive charge from low to high potential). This is performed by active ion pumps on the selectively permeable cell membrane and requires energy.

Consider the case where the inside of a cell is at -70 mV relative to the extracellular environment. A Na–K pump is required to move a Na+ ion out of the cell. Estimate the energy required. Repeat for a K+ ion. (20 marks)

Cell interior
Na+ 15 mM
K+ 150 mM
-70 mV
Cl- 10 mM
A- 100 mM
Na+ 150 mM
A- 0.2 mM
K+ 5 mM
Cl- 120 mM
Cell exterior
Cell exterior
Na+ Na+ Na+
Na+ Na+ Na+
K+ K+
K+ K+ K+
Diffusion
Na+ Diffusion
Na+-K+ pump
Plasma membrane
Cell interior

Added by Noelia N.

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