In this deck, we'll explore how substances get into and out of cells. Just like a house needs supplies to come in and rubbish to go out, a cell needs things like oxygen and glucose, and needs to get rid of waste like carbon dioxide. We will learn about the three main ways this happens: diffusion, osmosis, and active transport.

Let's start with diffusion. Imagine someone sprays perfume in one corner of a room. Soon, you can smell it everywhere. The perfume particles have spread out, moving from where they were most concentrated to where they were less concentrated. This is diffusion. In biology, diffusion is the net movement of particles from an area of high concentration to an area of low concentration.

Diffusion happens because particles are always moving randomly. Where there are more of them, they are more likely to bump into each other and spread out. This process doesn't require any energy from the cell. It's a passive process, like a ball rolling downhill.

Three main factors affect how quickly diffusion happens. First, the concentration gradient. This is the difference in concentration between two areas. A steeper gradient, meaning a bigger difference, makes diffusion faster. Second, temperature. Higher temperatures give particles more kinetic energy, so they move and spread out faster. Third, the surface area of the membrane they are crossing. A larger surface area provides more space for particles to pass through, speeding up diffusion.