gamma-Aminobutyric acid (GABA) is a neurotransmitter that is released into the s

Question

gamma-Aminobutyric acid (GABA) is a neurotransmitter that is released into the synaptic cleft during a nerve impulse. After the nerve impulse the GABA must be re-absorbed into the nerve cell to terminate transmission of the impulse. The re-uptake is accomplished by a Na-GABA symporter, which cotransports 3 Na+ for each GABA molecule. If the resting membrane potential is -60 mV (inside negative), the Na+ concentration outside the cell is 150 mM and 10 mM inside the cell, and the temperature is 37 °C, what is the maximum concentration gradient of GABA that can be achieved? ?

Explanation / Answer

Since the concentration of sodium outside the cell is 150 mM and inside the cell is 10mM so The concentration gradient of sodium is 150-10=140 mM. It means that the flow of the sodium will be towards the concentration gradient. Since GABA is cotransported with sodium so the GABA will also flow to the inside of the cell. The flow will be continue till the concentration becomes equal on both sides. Since NA-GABA symporter transport 3 sodium with 1 GABA, so maximum 23 mM of concentration can be achieved inside the cell. So maximum concentration gradient that can be achieved is 23 mM.

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