A cell has a membrane potential of 200 mV. To which side of the membrane will negatively charged molecules be attracted? Group of answer choices Neither The outside Both The inside
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A negative membrane potential inside relative to the outside means the inside is negative and the outside is positive. Show more…
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The plasma membrane of a cell has a surface charge density of 2 x 10-4 C/m2 on the outside and an equal magnitude, opposite sign charge density on the inside. The membrane is approximately 5 nm thick. (a) Is the potential difference from the inside of the cell to the outside positive or negative? Explain briefly. (b) How much energy is required for a sodium-potassium pump (the enzyme that transfers Na+ ions from the inside of the cell to the outside, and K+ from the outside to the inside) to transport three Na+ ions from the inside to the outside of the cell? (Assume the energy required is just equal to the electric potential energy gained by the Na+ ions in moving from the inside to the outside; ignore the energy associated with conformational changes to the enzyme.) The charge of each ion is the elementary charge.
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Remember that ions are electrically attracted to particles of opposite charge and are repelled by particles of the same charge. By electrical attraction alone, in what direction would A- tend to move if movement were possible? _______ A) into the cell B) outside the cell By diffusion alone, in what direction would A- ions tend to move if movement were possible? A) Out of the cell B) into the cell If a gated A- channel in the membrane opened up, in what direction would A- move? A) Out of the cell B) Into the cell C) Depends on the relative strengths of diffusion and electrical attraction The tendency of A- ion to move across the plasma membrane depends on the ___________. A) electrochemical gradient B) Osmotic potential C) turgor pressure. The following table presents the concentrations of these three charged particles inside and outside the cell: Charged Particle | Concentration (mM) Inside | Concentration (mM) Outside ------------------ | ------------------------ | ------------------------- K+ | 150 | 5 A- | 100 | 0 Na+ | 15 | 150 Remember that ions are electrically attracted to particles of opposite charge.
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3. ABOUT THE CELL MEMBRANE MODEL: Above the membrane will be EXTRACELLULAR. Below the membrane will be INTRACELLULAR. Green ball represents Na+. Blue diamond represents K+. Even though this model does not show any charges, you know that the unequal distribution of ions results in a membrane potential where the inside of the cell is negatively charged relative to the outside. This is due partly to the action of the Na+K+ ATPase which pumps out Na+ and pumps in K+. A K+ leak channel contributes to the membrane potential. How do they do this? Predict the direction of K+ movement through an open leak channel. Place a few K+ leak channels in the membrane and check your prediction.
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