Question

Describe how cell maintains resting membrane potential. Write out the steps taken in order to accomplish this.

Answer 1

Answer) Potential difference between the inside and the outside of the cell at rest, called as the resting membrane potential.

This is also termed as steady potential or transmembrane potential and indicates the resting state i.e state of polarisation of the cell membrane.

It is written with a minus sign, signifying that inside is negative relative to the exterior of the cell.

Resting membrane potential ranges from - 10 mV to - 100 mV.

Steps taken in order to accomplish resting membrane potential -

1) Resting cell membrane is effectively impermeable (or moderately permeable) to sodium (Na+) ions.

2) Resting cell membrane is freely permeable to potassium ( K+) and chloride (Cl-) ions (potassium permeability 50-100 times greater than sodium permeability)

3) Resting cell membrane is impermeable to most of the intracellular anions such as proteins and organic phosphate ions.

4) Resting cell membrane is negative inside and positive outside the membrane. It is due to distribution of ions across the cell membrane.

5) More potassium ions diffuses out of the cell (relative to entry of sodium ions into the cell), so sodium influx does not compensate for potassium efflux, because membrane at rest is much less permeable to sodium than potassium.

6) Chloride ions diffuses inwards into the cell down its concentration gradient.

7) Non-diffusible anions like proteins, phosphates stay in the cell as these are impermeable.

8) All these movement of ions in and out of the cell at rest creates a potential difference across the cell membrane. This is known as resting membrane potential.

9) There is slight excess of cations outside the membrane and slight excess of anions inside the membrane. So, resting membrane potential is negative inside.