Final answer:
A transporter that moves two ions or molecules in the same direction across a membrane is known as a symporter.
Step-by-step explanation:
When a transporter moves two ions in the same direction across the membrane, it is considered a symporter. A symporter, which is a type of secondary active transporter, typically moves two different substances across a cellular membrane in the same direction using energy derived from the electrochemical gradient of one of the ions, often sodium.
For instance, the sodium-glucose symporter moves sodium ions and glucose molecules together into the cell. The sodium ions move down their electrochemical gradient, providing the energy necessary for glucose to be transported into the cell against its gradient.
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