Introduction.

Biochemistry is the discipline that uses the principles and language of chemistry to explain biology at the molecular level.

In general the same chemical compounds and the same central metabolic processes are found in organisms as distantly related as bacteria and humans. In other words the basic principles of biochemistry are common to all living organisms.

We will find that much of our study is devoted to considering how enzymes and nucleic acids are central to the chemistry of life. In order to understand how nucleic acids store and transmit genetic information, we must understand their structure and their role in encoding the enzyme proteins which catalyze (speed up) the synthesis and degradation of bio molecules, including nucleic acids themselves.

Only six non-metallic elements – oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur account for more than 97% of the weight of most organisms. All these elements can form stable covalent bonds.

Water is a major component of cells and accounts for the high percentage of oxygen atoms. And some elements such as silicon, aluminum and iron are present only in trace amounts in cells.

Altogether, a total of 29 different elements are commonly found in living organisms. These include 5 ions that are essential in all species: calcium (Ca²⁺),  potassium (K⁺), sodium (Na⁺), Magnesium (Mg²⁺) and chloride (Cl^–).

The 29 Elements of Life encircled.

Important to biochemistry’s evolution was when in 1828 Friedrich Wohler synthesized the organic compound Urea by heating the inorganic compound ammonium cyanate. This experiment showed for the first time that compound found exclusively in living organisms could be synthesized from common inorganic substances. We now understand that the synthesis and degradation of biological substances obey the same chemical and physical laws as those outside biology. So no special processes are required to explain life at the molecular level.

Most of the solid material of cells consists of carbon containing compounds. The study of such compounds falls into the area of organic chemistry. There is many similarities between the discipline of organic chemistry and biochemistry, but organic chemists are more interested in reaction that take place in the lab (in vitro) where as biochemists would like to understand how reactions happen in living cells (in vivo).