By Monica 11C

Is the passive movement of molecules, atoms or ions along a concentration gradient, from a region of high concentration to a region of low concentration. An example of diffusion is the gas change at the alveoli, the oxygen from air to blood, carbon dioxide from blood to air. A sugar cube is placed in a glass of water will dissolve, the molecules (solute) of sugar will slowly spread throughout the water (solvent).

 Osmosis is the net movement of free water molecules through a semi-permeable membrane, from a solute of low concentrations to a solute of high concentrations  An example of osmosis is plants that absorb water and nutrients from the soil. The solution in the roots of plants draws not only water in but useful minerals that plants need to survive.  Osmosis is also vital in plant and animal cells, with fluids flowing in and out of the cell wall to bring in nutrients and carry out waste.

 Active transport is the energy demanding transfer to move substances across membranes against its concentration gradient. It takes energy for the cell to take something else in. transport of vesicles involve endocytosis and exocytosis.. It can be split in to transport by proteins and transport by vesicles.  Examples of active transport is the uptake of glucose in the intestines and the sodium-potassium pump.

 Facilitated diffusion is the passive movement across a membrane through a protein carrier, which makes the movement faster than it would be along the concentration gradient only. Substances travel from high concentrations to low concentrations.  Glucose is an example of facilitated diffusion as the protein carrier helps the glucose cross into the cell.

 Endocytosis is the process of taking particles in and engulfing them as part of the cell membrane. It is often used in most cells because important substances are large polar molecules that can’t pass through any other way.  An example is leukocytes that engulf foreign substances like bacteria.

 Exocytosis is the process in which the cell releases materials from within to the cytoplasm to the outside and discharging them as membrane-bound vesicles.  Some examples of exocytosis are secretion of protein like enzymes and antibodies from cells and recycling of plasma membrane bound receptors.

  booktransp.html booktransp.html  to/content/transportation-within-and-between-cells.html to/content/transportation-within-and-between-cells.html  astr.gsu.edu/hbase/kinetic/diffus.html astr.gsu.edu/hbase/kinetic/diffus.html  