Lynen, Feodor (1911-1976) was a German biochemist who studied how cells produce cholesterol and lipids, which are fatty substances. Lynen's experiments revealed the roles of certain enzymes, which are molecules that speed up chemical reactions, and the vitamin biotin in the formation of lipids. For this work, Lynen was awarded the 1964 Nobel Prize in physiology or medicine, which he shared with Konrad Emil Bloch, a German-born American biochemist.

Feodor Felix Konrad Lynen was born in Munich, Germany, on April 6, 1911, to Wilhelm and Frieda Prym Lynen. His father was a professor at the Munich Technical University. Lynen became interested in chemistry when his older brother installed a small laboratory in their home.

In 1921, after completing his elementary education, Lynen entered school in Munich. He enrolled in the University of Munich in 1930 and studied chemistry under Heinrich Otto Wieland, winner of the 1927 Nobel Prize in chemistry. He received his Ph.D. degree in chemistry in 1937. Lynen became a lecturer at the University of Munich in 1942. In 1947, he became associate professor, and in 1953 he was appointed full professor. In 1954, he accepted an additional appointment as director of the Max Planck Institute for Cell Chemistry, a leading research and training institute serving scholars in the field of biochemistry, and continued teaching at the university.

Lynen's most important research at the University of Munich focused on intermediary metabolism, cholesterol synthesis, and fatty acid biosynthesis. Metabolism involves all the chemical processes by which an organism converts matter and energy into forms that it can use. Metabolism supplies the matter—the molecular building blocks an organism needs for the growth of new tissues. These building blocks must either come from the breakdown of molecules of food, such as glucose (sugar) and fat, or be built up from simpler molecules within the organism.

Cholesterol is one of the fatty substances found in animal tissues. The human body produces cholesterol, but this substance also enters the body in food. Meats, egg yolks, and milk products, such as butter and cheese, contain cholesterol. Such organs as the brain and liver contain much cholesterol. Cholesterol is a type of lipid, one of the classes of chemical compounds essential to human health. It makes up an important part of the membranes of each cell in the body. The body also uses cholesterol to produce vitamin D and certain hormones.

All fats are composed of an alcohol called glycerol and substances called fatty acids. A fatty acid consists of a long chain of carbon atoms, to which hydrogen atoms are attached. There are three types of fatty acids: saturated, monounsaturated, and polyunsaturated.

Living cells manufacture complicated chemical compounds from simpler substances through a process called biosynthesis. For example, simple molecules called amino acids are put together to make proteins. The biosynthesis of both fatty acids and cholesterol begins with a chemically active form of acetate, a two-carbon molecule. Lynen discovered that the active form of acetate is a coenzyme, a heat-stabilized, water-soluble portion of an enzyme, called acetyl coenzyme A. Lynen and his colleagues demonstrated that the formation of cholesterol begins with the condensation of two molecules of acetyl coenzyme A to form acetoacetyl coenzyme A, a four-carbon molecule.

Lynen also clarified the function of biotin, a growth vitamin of the B complex. He researched the functions in the human body of biotin. Lynen's research revealed that biotin is important in the production of fat and other vital body substances.

Lynen and Bloch, who had immigrated to the United States in 1936, had both been researching cholesterol and related substances. Realizing this, the two scientists began to share their work. In 1964, they shared the Nobel Prize in physiology or medicine for their discoveries concerning the mechanism and regulation of cholesterol and fatty acid metabolism.

The cholesterol studies added to understanding of how an accumulation of cholesterol in the inner walls of arteries caused arteriosclerosis, heart attacks, and strokes. In 1964, the American Heart Association recommended that cardiac patients reduce their fat intake. The National Heart Association showed that people with high cholesterol levels developed more coronary disease more often.