Question

1. what is passive transport?

active transport during diffusion, molecules move randomly in all directions. a
few molecules move by chance from areas of low concentration to areas of high
concentration, but most molecules move toward areas of lower concentration. in
many cases, cells need the concentration of a molecule inside the cell to be
higher than the concentration outside the cell. in order to maintain this
difference in the concentration of molecules, cells use active transport. cells
supply the energy to do this work—just as you would supply the energy to pedal
your bike uphill. active transport is the movement of materials across a cell
membrane using cellular energy. as in facilitated diffusion, proteins within the cell
membrane play a key role in active transport. using the cell’s energy, transport
proteins “pick up” specific molecules passing by the cell and carry them across
the membrane. calcium, potassium, and sodium are some substances that are
carried into and out of cells by active transport.

Explanation:

The text focuses on active transport, but passive transport (not fully explained here) is the movement of substances across a cell membrane without cellular energy, like diffusion (molecules move from high to low concentration, no energy used) or facilitated diffusion (with transport proteins, still no energy).

Answer:

Passive transport is the movement of materials across a cell membrane without the use of cellular energy, typically occurring down a concentration gradient (e.g., diffusion, facilitated diffusion).