Which of the following is FALSE regarding the membrane potential?
in their resting state, all body cells exhibit a resting membrane potential
The resting membrane potential is maintained by solely by passive transport processes
The resting membrane potential occurs due to active transport of ions across the membrane due to the sodium-potassium pump.
The resting membrane potential is determined mainly by the concentration gradients and differential permeability of the plasma membrane to K and Na ions.
The Correct Answer is B
A. In their resting state, all body cells exhibit a resting membrane potential: Every living cell maintains an electrical charge difference across its plasma membrane. Even non-excitable cells display a resting membrane potential, though it is most significant in nerve and muscle cells.
B. The resting membrane potential is maintained solely by passive transport processes: Passive diffusion of ions contributes to membrane potential, but active transport is also required. The sodium-potassium pump actively moves sodium out and potassium in, counteracting passive leaks.
C. The resting membrane potential occurs due to active transport of ions across the membrane due to the sodium-potassium pump: The sodium-potassium pump is vital because it maintains the steep gradients of sodium and potassium. Without this active transport, the gradients would dissipate, eliminating the resting potential.
D. The resting membrane potential is determined mainly by the concentration gradients and differential permeability of the plasma membrane to K+ and Na+ ions: Potassium has the greatest influence since the membrane is more permeable to K+ at rest. Sodium also plays a role, but the relative permeability differences primarily shape the resting potential.
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Related Questions
Correct Answer is C
Explanation
A. Binding is limited to transport maximums: This concept applies to carrier-mediated transport where saturation can occur, but channel-mediated diffusion does not rely on binding and does not reach a transport maximum in the same way.
B. Substances bind to protein carriers: Carrier proteins facilitate movement by binding specific molecules and undergoing conformational changes. Channel-mediated facilitated diffusion does not involve this binding mechanism.
C. Substances move through fluid-filled, transmembrane proteins: In channel-mediated facilitated diffusion, specific substances pass through aqueous channels formed by transmembrane proteins. These channels allow ions or small polar molecules to move down their concentration gradients without energy input.
D. Facilitated active transport is necessary: Channel-mediated diffusion is passive and does not require ATP. Active transport involves energy to move substances against their concentration gradient, which is not the case here.
Correct Answer is B
Explanation
A. Sagittal: A sagittal plane divides the body into left and right portions, either equally or unequally, but does not separate anterior and posterior regions.
B. Frontal: The frontal (or coronal) plane is a vertical plane that divides the body into anterior (front) and posterior (back) sections, making it the correct choice.
C. Median: The median (midsagittal) plane is a specific sagittal plane that passes exactly through the midline, dividing the body into equal left and right halves, not front and back.
D. Transverse: The transverse (horizontal) plane divides the body into superior (top) and inferior (bottom) portions, not anterior and posterior.
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