Simple diffusion is like a kid wandering into my shop freely—no help needed, down the concentration gradient. Facilitated diffusion is like when I hold the door for a regular customer—still no energy, but needs a channel or carrier protein. Active transport? That's me hauling a sack of potatoes up the stairs against gravity, using my own ATP energy.
I'm drilling this into my head because in the kidney, reabsorbing glucose against its gradient is active transport, and if that pump fails, sugar spills into the urine—just like if I stopped working, the shop shelves would empty.
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