Something about fatty acid

[donaldcat]

Three fatty acid, when condense with glycerol, they donate or give out their OH- ions and combine with the H+ ions to form water and fat molecule. According to my chemistry teacher, an acid is a covalent molecular compound, which when dissolved in water, forms hydrogen ions H+ (aq). As fatty acid forms OH- when dissolved in water, why it is called as an acid but not an alkaline?

[Ouabache]

Three fatty acid, when condense with glycerol, they donate or give out their OH- ions and combine with the H+ ions to form water and fat molecule.

Actually, it is the carboxylic group -COOH that gives the acidity to fatty acids (http://www.biology.lsu.edu/introbio/Link2/fatty%20acids.gif). Just like HCl (hydrochloric acid) dissociates into H+ and Cl- in water, the carboxylic acid group (http://www.sp.uconn.edu/~bi107vc/fa02/terry/carboxyl.html) on a fatty acid, with dissociate into H+ and COO- making the solution acidic. This conforms to your teacher's definiton of an acid.

When fat synthesis occurs, the fatty acids each do contribuite an OH- and the glycerol 3 H+ to form a fat molecule (http://www.daviddarling.info/images/fat.jpg).