Suppose you discover a new bacterium that has a concentration of 15 nM Cu2+ inside the cell, and 1 mM Cu2+ outside the cell. When a facilitated diffusion Cu2+ transporter opens, you expect the Cu2+ ions to flow....(Remember, to move with/down a concentration gradient is to move from high to low concentration; against/up a concentration gradient is low to high.)- ○ inside the cell, with its concentration gradient- ○ inside the cell, against its concentration gradient- ○ outside the cell, with its concentration gradient- ○ outside the cell, against its concentration gradient

Diffusion is the movement of silute particles or molecules from the region of higher concentration to a region of lower concentration. The net movement of molecules occurs down the concentration gradient.Facilitated diffusion is the diffusion which is aided by a carrier protein or a channel protein. The carrier protein binds with the molecules and help in its transport across the hydrophobic core of the plasma membrane.This facilitated diffusion is a passive process and moves the molecules down the concentration gradient from higher concentration to lower concentration.In the given scenario, the concentration of Ca+2 ions is 15 nM inside the cell and it is 1mM outside the cell.1nM=10-6 mM 15 nM=1.5x10-5mM So the concentration of Ca+2 ions inside the cell is 1.5x10-5 mM and it is 1 mM outside the cell.So the concentration is higher outside the cell. The facilitated diffusion occurs from higher concentration to lower concentration down the concentration gradient. Hence the movement is from outside of the cell to the inside with / down the concentration gradient.Option 1 is correct. Inside the cell with its concentration gradient.Option b is incorrect because of the Ca+2 moved inside the cell it is down the concentration gradient as the concentration is higher outside . Option c and d are incorrect because the Ca+2 ions from outside to inside . If a facilitated diffusion occurs by a transporter protein , the movement is from outside of the cell to the inside with / down the concentration gradient because the concentration outside the cell is 1.5x10-5 mM inside and 1 mM insideOption 1 is correct. Inside the cell with its concentration gradient.