Final answer:
Sodium transmits electrical impulses through nerve cells by entering the cell and depolarizing the membrane during an action potential. It is the principal positively charged ion in the extracellular fluid and is actively transported by the sodium-potassium pump which requires ATP.
Step-by-step explanation:
The correct answer to the question 'Sodium ____' with the provided options would be B) Transmits electrical impulses through nerve cells. Sodium ions (Na+) are essential for the propagation of electrical signals in the nervous system. When a nerve impulse is initiated, sodium channels open, allowing Na+ to enter the cell and depolarize the membrane. This depolarization is critical for the generation of an action potential, which transmits the electrical impulse down the nerve cell. Sodium does not directly promote glycolysis or release energy from ATP; these processes involve different biochemical pathways and molecules.
Furthermore, sodium acts as the principal positively charged ion in the extracellular fluid, rather than the intracellular fluid. The sodium-potassium pump is a transport mechanism that uses ATP to pump sodium out of cells and potassium into cells, maintaining the necessary concentration gradient for nerve function. This pump is essential for the cell to regain its resting state after an action potential has passed.