Chlorophyll A, molecular model. This is the molecule used by plants to gather energy from sunlight. When light falls on the molecule, it loses an electron, transferring it to a series of adjacent biochemicals, eventually creating high energy molecules that can be used to convert atmospheric carbon dioxide to sugars, with oxygen as the waste product. This reaction is the basis for almost all life on Earth. Chlorophyll A is a chlorin molecule, comprising a porphyrin ring (upper right) surrounding a magnesium ion (green), with a long phytol side chain (left). Atoms are shown as balls and are colour coded: carbon (grey), oxygen (red), nitrogen (blue) and hydrogen (white).