Osmosis and Diffusion 7 th grade science Cells

Osmosis and Diffusion 7 th grade science

Cells have structures that protect their contents from the world outside. All cells are surrounded by a cell membrane that separates the cell from the outside environment. The cell membrane is selectively permeable cell membrane

selectively permeable membranes Selectively Permeable - some substances can pass through the membrane while others cannot

Substances can move into and out of a cell be one of three methods: • Diffusion • Osmosis • Active Transport

Substances can move into and out of a cell be one of three methods: • Diffusion • Osmosis • Active Transport

Diffusion – is the process by which molecules move from an area of higher concentration to an area of lower concentration – diffusion is the main method by which small molecules move across the cell membrane! What causes diffusion? Molecules are always moving and as a result, they bump into each other (collide). When collisions occur, molecules move push away from one another and spread out. Eventually, they will spread out evenly throughout the area.

Osmosis – is the diffusion of water molecules through a selectively permeable membrane – cells cannot function properly without water, so many cellular processes depend on osmosis **In osmosis, water molecules move by diffusion from an area of high concentration (a lot of H 2 O molecules) to an area of low concentration (few H 2 O molecules)**