Scientists Say: Amino Acid | Science News for Students

Scientists Say: Amino Acid

These tiny molecules wear many useful hats
Dec 4, 2017 — 6:30 am EST
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This is the basic structure of an amino acid. On the left is an amine, a nitrogen atom with two hydrogen atoms. On the right is a carboxyl, a carbon atom with two oxygen atoms and a hydrogen. In the center is the “R” group, a part of the molecule that is different for every type of amino acid.
YassineMrabet/Public Domain

Amino Acid (noun, “Ah-MEEN-oh AH-sid”)

This is a type of molecule found in living cells. Amino acids by themselves can serve as chemical messengers. When they link up into chains, amino acids form proteins, the engines that help our cells function.

Each amino acid is made of three parts. One is an amine, which is a nitrogen atom bound to two hydrogens. Another is a carboxyl group. This is a carbon atom with two oxygen atoms and one hydrogen atom. The third group is called the “R” group. The “R” group is a chain of atoms that is specific to each type of amino acid. It can be as simple as a single hydrogen atom, as in the amino acid glycine. Or it can be as complex as a big double ring of carbon atoms, like in the amino acid tryptophan (famously found in turkey).

Animals, including humans, need about 20 amino acids to construct all the proteins we require for survial. But we can only make about half of those in our own cells. Those are called nonessential amino acids, because our bodies can make them on their own. The others are essential amino acids. It’s essential that we get these amino acids from the food we eat.

In a sentence

A single amino acid change could be what makes Zika such a brain cell killer.   

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Power Words

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amino acids     Simple molecules that occur naturally in plant and animal tissues and that are the basic building blocks of proteins.

atom     The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

essential amino acids     A type of important nutrient, used to build proteins, that cannot be made by the body. It must be acquired from an animal’s foods.

hydrogen     The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nitrogen     A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn.

oxygen     A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

tryptophan     An amino acid needed for the growth of babies and to keep the levels of nitrogen in the adult body in balance. It is essential for health but cannot be made by the body. It must come from the foods we eat.