Chemical Level of Organization- Terms and Definitions

Atom

smallest stable unit of matter

Principle Elements

Elements required by the human body in relatively large amounts. Oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and iron.

Trace Elements

Elements present in the body in small amounts.

Atomic Number

The number of protons in the nucleus of an atom.

Atomic Mass

The total number of protons and neutrons in the nucleus of an atom.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Molecule

A chemical structure held together by covalent bonds.

Compound

A chemical substance made of atoms of two or more different elements, regardless of the type of bond joining them.

Inorganic Compound

A compound that generally does not contain carbon and hydrogen as its principal structural elements.

Organic Compound

A compound made from hydrogen and carbon. The guide identifies carbohydrates, lipids, proteins, and nucleic acids as the four major organic compound groups.

Ionic Compound

A bond created by the electrical attraction between oppositely charged ions. Metals and Non Metals

Covalent Bond

A bond in which one or more pairs of electrons are shared between atoms. Nonmetals and Nonmetals

Hydrogen Bond

A weak attraction between a partially positively charged hydrogen atom and a partially negatively charged atom.

Acid

A compound that dissociates in water and releases hydrogen ions.

Base

A compound that dissociates in water and releases hydroxyl groups; bases also remove hydrogen ions from a solution.

Salt

A compound that dissociates in water into cations and anions, neither of which is a hydrogen ion or hydroxyl group.

pH

A measurement of the hydrogen ion concentration of a fluid.

Buffer

A compound or system that helps maintain the pH of body fluids by removing or replacing hydrogen ions. It usually involves an acid and a base.

Carbohydrate

An organic compound composed of carbon, hydrogen, and oxygen; carbohydrates include sugars and starches and serve as a primary energy source for the body.

Monosaccharide

A simple sugar containing approximately 3–7 carbon atoms; it is the basic building block of carbohydrates. Ex. Glucose

Dissacharide

A carbohydrate made of two monosaccharides joined together. Ex. Sucrose

Polysaccharide

A more complex carbohydrate made of many sugar units; it may be straight or branched. Ex. Glycogen, Starch, cellulose

Lipid

An organic compound composed primarily of carbon, hydrogen, and oxygen. Major lipid classes include fatty acids, eicosanoids, triglycerides, phospholipids, and steroids.

Fatty Acid

A type of lipid that may be saturated or unsaturated, depending on the types of bonds between its carbon atoms.

Eicosanoid

A lipid that coordinates or directs local cellular activities and acts like a local hormone. Its effects vary by tissue and may include roles in pain sensations and labor contractions.

Triglyceride

A lipid formed from one glycerol molecule and three fatty acids; it is important for energy storage.

Phospholipids

A lipid containing a phosphate group that is a major component of the cell membrane bilayer.

Steroid

A lipid with a characteristic structure made of four connected carbon rings. Steroids include cholesterol and steroid hormones.

Protein

An organic compound made of long chains of amino acids linked together by peptide bonds. Proteins fold into specific three-dimensional shapes and perform functions such as support, movement, transport, buffering, regulation, coordination, and defense.

Amino Acid

The building block, or monomer, of proteins.

Peptide Bond

The bond that links amino acids together in a peptide or protein.

Enzyme

A biological catalyst that catalyzes chemical reactions that sustain life.

Nucleic Acid

An organic compound made of nucleotide building blocks; the two types are DNA and RNA.

DNA

Deoxyribonucleic acid; a nucleic acid made of nucleotides that stores genetic information.

RNA

Ribonucleic acid; a nucleic acid made of nucleotides that is involved in using genetic information to make proteins.

ATP

Ribonucleic acid; a nucleic acid made of nucleotides that is involved in using genetic information to make proteins.