Cytosolic calcium concentration is always a. Can be quite varied in a cell at re
ID: 3474859 • Letter: C
Question
Cytosolic calcium concentration is always a. Can be quite varied in a cell at rest. b. Mid-range, with capacity to increase or decrease with incoming signals. c. Very high in a cell at rest. d. Very low in a cell at rest. The voltage across the membrane at the point where sodium currents across the cell membrane in both directions are equal is called a. Resting membrane potential b. Equilibrium potential of the cell c. The reversal potential of potassium d. The Nernst potential of sodium e. The peak of the action potential In class, I described the Goldman equation is being sort of a weighted, composite version of the equation for equilibrium potential. How is the equation weighted within its own formula? a. For the membrane permeability of each individual ion b. For the diffusion coefficient in water of each individual ion c. For the size of each individual ion d. For the boiling temperature of each individual ion e. For the hydration sphere of each individual ion Which is essentially the flow of current within nerve cells? a. Graded potentials b. Action potential Which is generated by changes in current flow across the membrane of axons? a. Graded potentials b. Action potential Which is fastest? a. Graded potentials b. Action potential Which shows decrement in its amplitude as it travels? a. Graded potentials b. Action potentialExplanation / Answer
28. Ans. d
Cytoplasm is calcium concentration is always very low in a cell at rest (around 100 nM). On the other hand the calcium concentration is 20000 to 100000 fold higher in extracellular space.
29. Ans. d
Equilibrium potential or reversal potential of an ion can be defined as the voltage across the membrane at which point the net flow through any open pore is zero. This can be determined by Nernst equation.
Eion =RT/zF(ln ioninside /ionoutside)
where R=gas constant, T=temperature, z=ion charge, F=Faraday's constant
According to this Equilibrium concentration for sodium ion is +60mV (in mammalian neurons).
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