Here's a breakdown:
* Concentration Gradient: This refers to the difference in concentration of a substance between two areas. Imagine a room with a lot of people on one side and very few on the other. There's a concentration gradient of people.
* Passive Transport: Movement of substances across a membrane without using cellular energy is called passive transport. It happens naturally due to the concentration gradient.
* Down the Gradient: Substances tend to move from an area of high concentration to an area of low concentration. Think of the people in the room example – they naturally spread out until they are evenly distributed.
Examples of Passive Transport:
* Diffusion: The movement of molecules from a high concentration area to a low concentration area.
* Osmosis: The movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration.
Key Point: Passive transport doesn't require energy because the movement is driven by the natural tendency of molecules to distribute evenly.
