| The chlorophyll molecule consists of a flattish fairly square section composed of 5-membered rings (grey) with double C-C bonds, inside which are 4 nitrogens (blue), and a central magnesium (lime green).
This porphyrin structure is similar to the haem group in haemoglobin and myoglobin, which have an iron atom in the centre. Leading off from one corner is a long chain of carbon and hydrogen atoms called the phytol chain, a 20-carbon diterpene alcohol section which enables the chlorophyll molecule to be anchored in the membrane of the chloroplast. There are several forms of chlorophyll. This molecule is in fact chlorophyll A. Chlorophyll B, which has 2 closer absorption peaks, has an aldehyde -CHO group off to one side of the porphyrin structure, instead of the methyl group -CH3 (click to highlight). In photosynthesis, the function of chlorophyll is to absorb photons of light energy and to emit electrons. These are then passed to electron acceptors which pass on their energy to be used in the production of ATP and reduced NADP. These compounds are then used to reduce carbon dioxide in the light-independent reactions of photosynthesis. Frieda Reichsman's view of chlorophyll absorbing a photon and emitting an electron (uses the same molecule definition file) |