Biology Key Points - Movement in and out of cells
Diffusion
Diffusion is the net movement of particles (of a gas or any particles in a solution) from region of high
concentration of particles to a place with a low concentration of particles. This can also be said as
down a concentration gradient. Diffusion is a passive process which means that no energy is
required in the process. Diffusion happens due to the random movement of particles. Diffusion
happens faster at higher temperatures because the particles have more energy and so it can move
quicker than at cooler temperatures.
An example of diffusion at work is when you spray the air freshener at one corner of the room. Over
time the scent of the air freshener will spread across the room because of diffusion.
Osmosis
Osmosis is the net movement of water from a place high concentration of water molecules to a
place of low concentration of water molecules across the partially permeable membrane from a
dilute to a concentrated solution of solute. In layman’s terms, it is diffusion but with water
molecules.
There are some terms linked with osmosis:
Hypertonic – the concentration of solutes in the solution outside the cell is higher than in the cell
itself ( causes osmosis to happen outside the cell)
Hypotonic – the concentration of the solute in the solution outside the cell is lower than in the
actual cell (causes osmosis to happen in the cell)
Isotonic – the concentration of the solute in the solution outside the cell is the same as inside the
cell ( no osmosis happens)
Flaccid- cells are no longer firm and swollen.
Diffusion
Diffusion is the net movement of particles (of a gas or any particles in a solution) from region of high
concentration of particles to a place with a low concentration of particles. This can also be said as
down a concentration gradient. Diffusion is a passive process which means that no energy is
required in the process. Diffusion happens due to the random movement of particles. Diffusion
happens faster at higher temperatures because the particles have more energy and so it can move
quicker than at cooler temperatures.
An example of diffusion at work is when you spray the air freshener at one corner of the room. Over
time the scent of the air freshener will spread across the room because of diffusion.
Osmosis
Osmosis is the net movement of water from a place high concentration of water molecules to a
place of low concentration of water molecules across the partially permeable membrane from a
dilute to a concentrated solution of solute. In layman’s terms, it is diffusion but with water
molecules.
There are some terms linked with osmosis:
Hypertonic – the concentration of solutes in the solution outside the cell is higher than in the cell
itself ( causes osmosis to happen outside the cell)
Hypotonic – the concentration of the solute in the solution outside the cell is lower than in the
actual cell (causes osmosis to happen in the cell)
Isotonic – the concentration of the solute in the solution outside the cell is the same as inside the
cell ( no osmosis happens)
Flaccid- cells are no longer firm and swollen.
