Organic molecules

ORGANIC MOLECULES

There are so many molecules possible in nature—from individual atomic molecules (which are as numerous as the number of elements in the periodic table) to very large macromolecules made from at least a thousand different atoms that have somehow found themselves together in not only the same vicinity but connected to one another in a very specific way.

There are thousands of possible combinations of atoms in nature; the vast majority of the molecules in nature have only four different atoms in them: these are carbon, hydrogen, oxygen, and nitrogen. In fact, it can easily be said that, of these, it is carbon that defines life as being life and that defines a given molecule as being “organic” or belonging to life. Of course, there are other atoms in life, such as sulfur, phosphorus, and minerals like magnesium, iron, and zinc. These arguably are necessary for life but, at least here on earth, they do not define life. (As you’ll see, water is necessary for life as well but in a different way).

Organic molecules are completely built upon chains of carbon atoms. These chains, at least in life forms as we know them, are extremely long. You may ask, why carbon and what’s so special about it? Without getting deep into biochemistry, suffice it to say that carbon has the unique ability to bind to four other atoms at the same time. This leads to chains of carbon atoms that can combine to connect to other carbon atoms as well as to other molecules. Carbon has the unique property of also being able to form rings rather than lining up in single file. This ability to combine with other atoms as well as to form rings makes for an incredible variety of different molecules that can be made from it.

You should know that organic molecules aren’t confined to living things. There are many carbon-based things in nature, such as fossil fuels, which are actually the remains of living organisms that once survived on earth. Manmade molecules, such as pesticides, medicines, and plastic substances are considered organic because of their molecular structure. There are organic components to much of what we see in life around us, such as cologne, shampoo, rayon fabric, nylon fabric, cotton, detergent, and cleaning products.

There are some inorganic molecules that are intimately connected to life but aren’t in themselves organic. These include carbon dioxide (CO2), oxygen (O2), and water (H2O). Life would not exist without these molecules and yet, because they do not involve a chain of carbon atoms, they are inorganic. These can be considered, however, to be the building blocks of life. Plants use carbon dioxide and water to make carbon-based molecules called carbohydrates.

Carbon has six protons and six electrons. Four of these six electrons are available for bonding. When it comes to biochemical life forms, carbon can form four “single bonds”, two single bonds and a “double bond” or two double bonds. It depends on the demands of the other atoms in the molecule. For example, oxygen has two “spots” to connect with other atoms. It can connect with two carbon atoms with two single bonds or with one carbon atom in a double bond (which means the sharing of 2 electron pairs at once). This is why oxygen, which is unstable by itself, is generally seen in living things as O2 (two molecules together).

One of the more basic carbon-based molecules is CO2. This involves carbon simultaneously “double-bonding” with two oxygen molecules. This is a completely stable molecule in that it uses up free electron pairing spots for both carbon and oxygen. Another simple carbon-based molecule is methane, which is CH4. This involves hydrogen, which has just one electron to share and carbon, which has four free electrons to share. The result is the stable molecule of methane. While we’re on the subject of pairing, you should know that nitrogen has three extra electrons available for pairing. This leads to a simple molecule of ammonia, which is NH3. This isn’t an organic molecule but it gives you an idea of what nitrogen needs as part of a molecular structure.