give some examples of a situation when a substance can not be moved in to cell
by osmosis or diffusion and how active transport solve the problem

Answer:Explanation:This is how the two processes differ from one another. One significant distinction between osmosis and diffusion is that only the solvent molecules (water molecules) pass the membrane during osmosis, but in diffusion, both solvent and solute particles are free to move. Passive transport in the case of diffusion does not require a transport protein to enter a cell. Gaseous molecules are transported by diffusion, or the gradient of concentration, from their higher to lower concentration. Energy is not used during passive transport.