Question

When neurons "fire," the first thing that happens is that sodium ions enter the cell. this does not require an input of energy. what can you infer from this?

Answer 1

Answer;

One can infer that membrane transport proteins are required in order for neurons to fire.

Explanation;

Transport proteins are proteins that transport substances across biological membranes. Transport proteins are found within the membrane itself, where they form a channel, or a carrying mechanism, to allow their substrate to pass from one side to the other.

-Transport proteins transport materials such as; ions such as sodium and potassium; sugars such as glucose; proteins and messenger molecules; and many more. In neurons, they  play a fundamental role in the functioning of nerve cells. These transporters, a third class of membrane transport proteins, move a wide variety of ions and molecules across cell membranes.