考研必备：考研写作1500词(101)

　　image - a reproduction of the appearance of a person or thing

　　laser - an instrument that makes a thin, powerful light

　　magnet - a piece of iron or other material that has a pulling force; this pulling force is called magnetism

　　molecule - the smallest amount of a chemical substance that can exist

　　nerve - a thin piece of tissue that sends information through the body to and from the brain

　　nucleus - the center part of an atom or cell

　　nucleic acid - a molecule that holds the genetic information necessary for life; there are two kinds of nucleic acid: DNA and RNA

　　nutrient - a food or substance that makes plants, humans or animals grow

　　organ - a part of the body that has a special purpose, such as the heart or brain

　　organism - a living thing, often so small it can be seen only through a microscope

　　particle - a very small piece of matter

　　proteins - substances responsible for the growth of tissue and for fixing damaged tissue

　　robot - a machine that moves and performs tasks

　　tissue - living material; a group of cells that are similar in appearance and do the same thing

　　virus - a kind of organism that causes disease

　　x-rays - a kind of radiation that can pass through most solid materials, often used in medicine