C4H6O5

C4H6O5 is the molecular formula for several chemical compounds, most notably malic acid. Malic acid is a dicarboxylic acid that plays a significant role in cellular metabolism. It is found naturally in fruits such as apples, from which its name is derived (from the Latin word "malum" meaning apple). It is responsible for the sour taste of many fruits.

In biological systems, malic acid is an important intermediate in the Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid cycle. This cycle is a central pathway in cellular respiration, where it generates energy in the form of ATP. Malic acid is also involved in gluconeogenesis, the metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates.

Beyond its biological functions, malic acid is widely used in the food industry as an acidulant and flavor enhancer. It is often added to beverages, candies, and baked goods to impart a tart taste. It can also be found in some cosmetic products as an alpha-hydroxy acid (AHA), contributing to exfoliation of the skin. Due to its role in metabolism and its presence in common foods, malic acid is generally considered safe for consumption and is regulated by food safety authorities.