Activation energy is required to start a chemical reaction. Activation energy is the energy needed to allow the reactant to react. Activation energy is measured in Joules (J).
Facilitated diffusion
<span>The word 'diffusion' means free movement across distance, with or without the presence of a barrier. However, there is a phenomenon known as facilitated diffusion which occurs at the cellular level. The cell does not allow free radicals and other harmful substances to enter and harm the cell organs. This is possible due to the structure of the cell membrane. The structure is such that, it allows only certain things to pass in and out of the cell. One such activity that allows selective movement in and out of the cell is the process of facilitated diffusion.</span>
Since living organisms require energy and both survival and reproduction... the sun provides the energy for photosynthesis. Cells need sugar as a sources of energy. The cellular respiration is the synthesis of ATP using energy that is being released by the breakdown of sugar to carbon dioxide and water.
