The sodium ion looked shocked. It had been going the wrong way, against the current. But the pump didn't care. It cracked another ATP. Heave . Another ion. Heave . Against the flow. Uphill. Spending energy like a miser spends gold.
Active transport was a protest.
Jamie wasn't looking at a glass of water anymore. The glass was the cell. The water was the outside environment. And inside the glass, the phone's battery icon was a tiny, red, flashing . explanation of active transport
But the phone was dead. The phone needed sodium. Not outside the glass. Inside . The phone was the cell’s mitochondria, screaming for fuel. The sodium had to get into the glass, against its natural drift. The sodium ion looked shocked
And then Jamie saw it. Not with eyes, but with imagination. It cracked another ATP
Jamie’s eyes widened. That was the gradient. The concentration was higher outside. The molecule wanted to stay out. But the cell needed it in.