E & F

enzyme [in zime]

A protein that triggers chemical reactions in the body

esophagus [e sof u gus]

The tube that passes food and drink from the mouth to the stomach

fat

A soft substance made of a mixture of lipids that is found in organic tissue

feces [fee sees]

Body wastes excreted from the digestive tract

fiber [fi bur]

The part of food that can't be digested by humans and passes through the intestine basically unchanged. Fiber helps move waste through the digestive system more quickly.

filtrate [fil trat]

The material that has passed through a filter.

free radical [free • rad i kal]

An atom or a group of atoms that have unpaired or "free" electrons. Free radicals are very reactive. They cause a reaction called oxidation. One example of oxidation is rust. Oxidation is harmful to the human body.