diffusion, osmosis, and active transport

diffusion

the net movement of particles from an area of higher concentration to an area of lower concentration (passive process)

osmosis

the net movement of water molecules across a partially permeable membrane from an area of higher concentration of water to an area of lower concentration of water

active transport

The net movement of particles from a low concentration to a high concentration (against the concentration gradient) across a membrane, with the use of energy from respiration.

example of active transport

in the root hair cells of a plant: plants need to absorb lots of water and mineral ions in order to survive which it obtains from the soil. To help with this plants have networks of roots that protrude into the ground and on those roots are root hair cells. They absorb water and mineral ions and are adapted to the role as they have long hair like protrusions giving the cells a large surface area for absorption. The minerals they need to absorb are at a higher concentration inside the cell than they are outside in the soil. So they can’t use diffusion, they have to use energy to absorb them by active transport against their concentration gradient. This energy comes from cellular respiration which happens in mitochondria so (another adaptation is that) root hair cells have lots of mitochondria.

down a concentration gradient

high concentration to low concentration

against a concentration gradient

low concentration to high concentration