Question

Describe what kind of membrane proteins are involved in (1) maintaining the sodium and potassium concentrations inside a neuron cell and (2) generating an action potential?

Answer 1

Voltage Gated Ion channels (VG channels) , Sodium -Potassium pump, Passive Ion channels,ligand gated channels are key membrane proteins in neurons and are involved in

1)maintaining sodium and potassium concentraion inside a neuron cell as well as 2)generating action potential

1)At resting stage ,the membrane is more permeable to K+ ions than Na+, there are more Na+ outside a neuron and more K+ inside the cell. There is a negative ion concentration inside the cell at resting potential by varied distribution of Na+ and K+ at both sides of the cell. The passive channels allow slow permeability of Na+ into the cell, and K+ outside the cell, while the sodium potassium pumps more K+ inside the cell and more Na+ outside the cell simalteanously. During the resting stage, Voltage gated sodium and potassium channels are closed.

The Sodium Potassium pump has significant role in maintaining action the respective ion concentration across the membrane.It used ATP hydrolysis to move Na+ and K+ uphill, i.e against their electrochemical gradient.Per ATP hydrolysis, 3Na+ are moved out of the cell and 2K+ are transported inside the cell from outside.

These transmembrane proteins are key in transporting this ions across membranes which cannot otherwise traverse through the hydrophobic membrane.

2)The VG channel for Na+ as two gates (Ni) or activation gate - that is normally closed but opens when cells gets more positive and gate (Nii) or decativation gate that is mostly open but is closedwhen cell gets too positive.

VG for K+ has only one gate (Ki), which is mostly closed but is opened if cell gets too positive.

Action potential arises, when a trigger like release of neurotransmitters near dendrites triggers flow of positive ions to move into the cell, they can bring the polarity to zero (depolarization). When the charge is positive enough,VG Na+ can be activated triggering action potentials