MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Molecular model of citric acid. Atoms are represented as spheres and are colour-coded: carbon (black), hydrogen (white), oxygen (red). The bonds between them are represented by rods, where two rods shows a double bond. Citric acid is a weak, organic acid that occurs naturally in citrus fruits such as oranges and lemons. It is a natural preservative and is also used to add an acidic, or sour, taste to foods and soft drinks. In biochemistry, it is involved in the citric acid cycle, an important stage in the metabolism of almost all living things.
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