A potential difference of 100 mV exists between the inner and outer surfaces of a cell membrane. The inner surface is negative relative to the outer surface. How much work is required to eject a positive sodium ion (Na ) from the interior of the cell

1.602 × 10⁻²⁰ J

Explanation:

Since the sodium ion Na has a positive charge, the work done in moving it from the interior of the cell to the exterior of the cell is W = qΔV where q = charge on sodium ion = +1 and ΔV = potential difference between inner surface of the cell and outer surface of the cell. Since the inner surface of the cell is negative relative to the outer surface, the sodium ion moves from a lower potential to a higher potential. So, the potential difference is ΔV = + 100 mV = 0.1 mV = 10⁻¹ V

Also, q = +1 which is one unit of charge. So, q = +e where e = electron charge = +1.602 × 10⁻¹⁹ C

So, W = qΔV (Note that the work done is positive since we have to input work into the cell to move a positive charge from lower to higher potential)

So, substituting the values of the variables into the equation, we have

W = qΔV

W =  +1.602 × 10⁻¹⁹ C × 10⁻¹ V

W =  +1.602 × 10⁻²⁰ J

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!

the water is warmed up by the sun and then it evaporates into the atmosphere. the sunlight warms the water by its heat. water is then cooled down and condensation takes place. the water then finally returns back to the earth by the process of precipitation in the form of rain or ice.

explanation: