Penny, an Active Transport protein, smiled. She was built differently than Trevor. She had a binding site for a tiny, high-energy battery called .
This was . The city needed Glucose, and there was plenty of room inside. Trevor didn't need to use any energy; he simply provided the tunnel. Glucose slid through Trevor’s watery core and popped out into the cytoplasm, ready to power the city. function of transport protein
"I can't go out there," Sodium whined. "It’s too crowded! It goes against the gradient!" Penny, an Active Transport protein, smiled