Life depends on the ability of cells to harvest energy from importing, processing, and exporting molecules

For something to be classed as a living organism, they must possess all of the seven characteristics that are shown in the table below.

Movement All living organisms can deliberately move their bodies or individual parts to change position.
Reproduction All living organisms are able to generate the next generation by reproducing organisms, that are the same kind as themselves.
Sensitivity All living organisms must be able to detect, and react to, the changing variables within their surroundings, internally and externally.
Growth All Living organisms develop and create adhering to particular directions coded within their genetics, allowing them to change size and shape.
Respiration The compound response that separates supplement particles in cells to produce energy.
Excretion All living organisms produce waste products.
Nutrition All living organisms requires energy. They take in nutrition to produce energy, to grow and repair.

Below is an illustration which shows simple diffusion. Simple diffusion is when molecules travel from a place which has a lot of molecules to a place that either lacks or has low amounts of molecules. They do this by travelling down through the membrane until both places have, more or less equal amounts of molecules. Molecules that travel through the simple diffusion method must be nonpolar and they must be small in size.

Below is an illustration which shows facilitated diffusion. Facilitated diffusion is different to simple diffusion because the molecules can not travel directly through the membrane. In order to go from a place which has lots of molecules to a place which lacks or doesn’t have many molecule, it needs to use a channel. This channel is named a protein channel and it provides the molecules a way of getting through to the membrane.

Below is an illustration that shows active transport. Active transport is not the same as simple diffusion or facilitated diffusion because it requires adenosine triphosphate, which is also known as ATP. This is the energy that is used to assist the molecules to travel from a place which has a lot of molecules to a place that either lacks or doesn’t have a lot of molecules. Active transport molecules are also different because they have to move against the gradient, which is why they require the use of energy.