Chemistry of Life Chapter 2

Introduction to Biochemistry Biochemistry is the study of structure, composition (what things are made up of), and chemical reactions that occur in living things. Living things (biotic factors) depend on chemistry to carry out life processes, so biology and chemistry are closely related!

Living things consist of atoms of different elements. Matter is anything that has mass or takes up space. Matter is made up of small units called atoms. Atoms are made up of 3 subatomic particles: Protons (which have a + charge) Electrons (which have a – charge) Neutrons (which have no charge) Together these substances help form matter!

Elements When atoms of the same type come together they make up units called elements. Elements cannot be broken down into simpler substance by ordinary chemical means. An element is a pure substance made of only 1 type of atom (it is usually abbreviated by a chemical symbol):

Examples: NaCl (salt) | H2O (water) | CO2 (carbon dioxide) Chemical Compounds Remember that elements are made up of small units called atoms. When these elements come in close contact with each other, they often have an “attraction” – like magnets. The attraction of these elements often leads to a bond: the joining of atoms to one another. When two or more elements are put together, they form a chemical compound. These compounds are usually represented by a chemical formula: a combination of chemical symbols that represent the joining of these elements. Examples: NaCl (salt) | H2O (water) | CO2 (carbon dioxide)

Chemical Bonds The atoms in compounds are held together by chemical bonds. Bond formation involves the electrons that surround each atomic nucleus. Electrons that are available to form bonds are called valence electrons. The main types of chemical bonds are ionic bonds and covalent bonds.

Ionic Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another: An atom that loses electrons is no longer neutral, instead it becomes positively charged. An atom that gains an electron is no longer neutral, instead it becomes negatively charged. These positively and negatively charged atoms are called ions.

Covalent Bonds Sometimes electrons are shared by atoms instead of being transferred: These electrons are located in a region between the atoms. A covalent bond forms when electrons are shared between atoms. The structure that results when atoms are joined together by covalent bonds is called a molecule (this is the smallest unit of most compounds).

Review Ionic & Covalent Bonds IONIC BONDS: electrons are transferred between atoms COVALENT BONDS: electrons are shared between atoms

Elements found in living things Carbon Hydrogen Oxygen Nitrogen Phosphorus Sulfur