Notes

Transport can be either passive or active. Passive transport is the movement of substances across the membrane without any input of energy by the cell. Active transport is the movement of materials where a cell is required to expend energy. In the case of this lab the discussion will be centered on passive transport.
The simplest type of passive transport is diffusion. Diffusion is the movement of molecules from an area of higher to an area of lower concentration without any energy input. Diffusion is driven by the kinetic energy found in the molecules. Diffusion will eventually cause the concentration of molecules to be the same throughout the space the molecules occupy, causing a state of equilibrium to exist.
Another type of passive transport is that of osmosis. Osmosis is the movement of water across a semi-permeable membrane. The process by which osmosis occurs is when water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration. The direction of osmosis depends on the relative concentration of the solutes on the two sides. In osmosis, water can travel in three different ways.
If the molecules outside the cell are lower than the concentration in the cytosol, the solution is said to be hypotonic to the cytosol, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytosol, the solution is said to be hypertonic to the cytosol, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytosol, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water.
In osmosis the cell is selectively permeable, meaning that it only allows certain substances to be transferred into and out of the cell.