Final answer:
A symporter is a type of membrane protein that transports two different substances in the same direction, while an antiporter transports them in opposite directions.
Step-by-step explanation:
A symporter is a type of integral membrane protein that transports two different substances across the cell membrane in the same direction. On the other hand, an antiporter also transports two different substances, but in opposite directions.
For example, the sodium-glucose symporter found in the small intestine and kidney cells allows sodium ions and glucose molecules to enter the cell together. The sodium ions move down their concentration gradient while simultaneously pulling the glucose molecules against their concentration gradient.
If the orientation of a symporter in the membrane were reversed, it would function as an antiporter, transporting the same substances but in opposite directions.