Serotonin

Serotonin, neurotransmitter, or chemical that transmits messages across the synapses, or gaps, between adjacent cells. Among its many functions, serotonin is released from blood cells called platelets to activate blood vessel constriction and blood clotting. In the gastrointestinal tract, serotonin inhibits gastric acid production and stimulates muscle contraction in the intestinal wall. Its functions in the central nervous system and effects on human behavior—including mood, memory, and appetite control—have been the subject of a great deal of research. This intensive study of serotonin has revealed important knowledge about the serotonin-related cause and treatment of many illnesses.

Serotonin is produced in the brain from the amino acid tryptophan, which is derived from foods high in protein, such as meat and dairy products. Tryptophan is transported to the brain, where it is broken down by enzymes to produce serotonin. In the process of neurotransmission, serotonin is transferred from one nerve cell, or neuron, to another, triggering an electrical impulse that stimulates or inhibits cell activity as needed. Serotonin is then reabsorbed by the first neuron, in a process known as reuptake, where it is recycled and used again or converted into an inactive chemical form and excreted.

Casein

Casein, group of proteins precipitated when milk is mildly acidified. Casein constitutes about 80% of the total proteins in cow's milk and about 3% of its weight. It is the chief ingredient in cheese. When dried, it is a white, amorphous powder without taste or odor. Casein dissolves slightly in water, extensively in alkalies or strong acids.

Casein is used as a food supplement and as an adhesive, a constituent of water paints, and a finishing material for paper and textiles. A variety of casein, known by the modified name paracasein, is preferred for making a plastic, through the reaction of the casein with formaldehyde, that goes into the manufacture of buttons and other small objects. It is produced by adding the enzyme rennin to milk, forming a precipitate different from the material precipitated by acids.

Calorie

Calorie, metric unit of heat measurement. The small, or gram, calorie (cal) is usually specified in science and engineering as the amount of heat required to raise the temperature of 1 g of water from 14.5° to 15.5° C. The temperature interval is sometimes specified in other ways. The definition now generally accepted and standard in thermochemistry, is that 1 cal equals 4.1840 joules (J).

A slightly different calorie is used in engineering, the international calorie, which equals 1/860 international watt-hour (W h). A large calorie, or kilocalorie (Cal), usually referred to as a calorie and sometimes as a kilogram calorie, equals 1000 cal and is the unit used to express the energy-producing value of food in the calculation of diets.