Atoms, isotopes, ions, and molecules: the building blocks  (Page 11/9)

"Through the discovery of Buchner, Biology was relieved of another fragment of mysticism. The splitting up of sugar into CO ₂ and alcohol is no more the effect of a 'vital principle' than the splitting up of cane sugar by invertase. The history of this problem is instructive, as it warns us against considering problems as beyond our reach because they have not yet found their solution."

Loeb is referring to the Nobel Prize-winning experiments of Eduard Buchner, who proved that cells are not necessary for cellular chemical reactions to take place. This was one of the crucial steps toward the synthesis of biology and chemistry that culminates in the modern-day discipline we call biochemistry. The properties of matter are important in the study of biochemistry (and biology), so we need to introduce some chemical concepts to help us with that understanding. At its most fundamental level, life is made up of matter. Matter is any substance that occupies space and has mass. Elements are unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances by ordinary chemical reactions. There are 118 elements, but only 92 occur naturally. The remaining elements have only been synthesized in laboratories, and are unstable.

Each element is designated by its chemical symbol , which is a single capital letter or, when the first letter is already “taken” by another element, a combination of two letters. Some elements follow the English term for the element, such as C for carbon and Ca for calcium. Other elements’ chemical symbols derive from their Latin names; for example, the symbol for sodium is Na, referring to natrium , the Latin word for sodium.

The four most abundant elements in all living organisms are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). In the non-living world, elements are found in different proportions, and some elements common to living organisms are relatively rare on the earth as a whole, as shown in [link] . For example, the atmosphere is rich in nitrogen and oxygen but contains little carbon and hydrogen, while the earth’s crust, although it contains oxygen and a small amount of hydrogen, has little nitrogen and carbon. In spite of their differences in abundance, all elements and the chemical reactions between them obey the same chemical and physical laws regardless of whether they are a part of the living or non-living world.

The structure of the atom

To understand how elements come together, we must first discuss the smallest component or building block of an element, the atom. An atom is the smallest unit of matter that retains all of the chemical properties of an element. For example, one gold atom has all of the properties of gold in that it is a solid metal at room temperature. A gold coin is simply a very large number of gold atoms molded into the shape of a coin and containing small amounts of other elements known as impurities. Gold atoms cannot be broken down into anything smaller while still retaining the properties of gold.