Chemistry Tutorial

Chemistry Tutorial

Basic Chemistry for Understanding Biology

An example of biochemistry

Biology and medicine have enjoyed enormous benefit from a biochemical approach to life. One striking example uses the fact that spinning nuclear protons can be regarded as simple magnets, and interact with an external magnetic field in a way that depends on their environment. To the right is an MRI scan of the head of a human using technology based on these principles. The technology produced high quality images of soft tissue.

A review of the basic chemistry of small molecules

The names of the elements are abbreviated. Often, the abbreviation makes perfect sense (C for carbon) and sometimes it does not (Na for sodium). There is an abundance of elements on earth and in living systems, but only 4 elements make up 99% of living organisms. These elements are hydrogen (H), oxygen (O), nitrogen (N), and carbon (C), and they are special in that they are 1) available and 2) suitable.

Graph of elements making up organisms and earth's crust

Terms to know

Element: matter composed of atoms that all have the same atomic number (protons).
Atom: the smallest component of an element that still has properties of the element, consisting of a positively charged nucleus surrounded by a charged cloud of electrons.; "+" and "-" charges strongly attract.
Proton: particle in the nucleus with a positive charge of +1 and an atomic mass number of 1 Dalton.
Neutron: a non-charged nuclear particle with the same mass as the proton.
Electron: negatively charged particle (-1) with a mass 1/1837 of that of a proton.
Isotope: atoms with the same number of protons and electrons, but different numbers of neutrons.

Electrons determine chemical properties of elements

Electrons are outside the nucleus, and determine properties of the atom. Chemical reactions involve sharing or exchanging electrons. Electrons move about the nucleus in atomic orbitals. Absorption of energy can cause an electron to move up to a higher energy level. The atom is stable when the outermost energy level of most atoms has eight electrons. Electrons can be transferred carrying energy to another molecule. The H atom can carry electrons for transferring energy. Oxygen has a strong affinity for electrons. Redox reaction transfer of electrons from one molecule (oxidized) to another (reduced). Stability can be achieved by adding, losing, or sharing electrons.

Illustration of electrons moving about the nucleus of a carbon and an oxygen molecules

Sharing electrons leads to the formation of covalent bonds. In the table to the right, you'll see the bonding patterns of the primary biologically important elements. Bonds contain energy, and a require energy to be broken. Bond energy (expressed as kcal/mole) is the energy required to break a bond. For example, an H-H bond requires 104 kcal/mole to break.

Bonding Patterns

element	number of covalent bonds
H	1
O	2
N	3
C	4
S	5

The Biology Project
Department of Biochemistry and Molecular Biophysics
The University of Arizona
January 28, 2003
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