Movement of Substances Into and Out of Cells

Movement of Substances Into and Out of Cells

Diffusion

• Diffusion is the process by which particles spread out from a region of high concentration to a region of low concentration.
• It is a passive process, meaning it does not require energy. Particles move down their concentration gradient.
• Factors that affect the rate of diffusion include temperature, particle size, and concentration gradient.

Osmosis

• Osmosis is the diffusion of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution) across a semi-permeable membrane.
• Similar to diffusion, osmosis is a passive process and does not require energy.
• It is vitally important in the transport of fluids in living organisms, such as the absorption of water in the gut and root hair cells in plants.

Active Transport

• Active transport is the movement of particles from a region of low concentration to a region of high concentration against the concentration gradient.
• Unlike diffusion and osmosis, this process requires energy, as substances are being moved against their concentration gradient.
• Examples of active transport include the absorption of glucose by the epithelial cells of the intestine and the uptake of mineral ions by plant root hairs.

Facilitated Diffusion

• Sometimes, molecules are not able to pass directly through the cell membrane. They rely on a method called facilitated diffusion.
• This process involves the use of protein channels or carrier proteins in the cell membrane to help the molecules cross.
• This is still a type of passive transport as it does not require energy.