Question

Biologically, how expensive are you? The elements that make up the typical adult body can be purchased from chemical supply companies for about $3,000-$4,000. However, each of those elements must be chemically bonded to together to produce the complex biological molecules of life (proteins, nucleic acids, carbohydrates, lipids). Using sophisticated laboratory equipment, highly trained scientists can synthesize these complex biological molecules from basic elemental building blocks, but this costs millions of dollars!

Consider the differences in worth between the elemental and biomolecular components of life. Explain the difference in terms of the characteristics of life.

Answer 1

From the mightiest blue whale to the most miniscule paramecium, life as we know it takes dramatically different forms. Nonetheless, all organisms are built from the same six essential elemental ingredients: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur (CHNOPS).

First off, carbon enters easily into bonds with other carbon atoms. This means it forms vast chains that act as a nice skeleton for other atoms to bond. In other words, carbon atoms are the perfect building blocks for large organic molecules. "This lends itself to complexity."

But what explains the other five chemical ingredients of life? "One thing that makes nitrogen, hydrogen and oxygen good is that they're abundant. They also exhibit acid-base effects, which allows them to bond with carbon to make amino acids, fats, lipids and the nucleobases from which DNA and RNA are built.

Sulfur provides electron shuffle. Basically, with their surplus of electrons, sulfides and sulfates help catalyze reactions. Some organisms use selenium in place of sulfur in their enzymes, but not many.

Last but not least, phosphorus, usually found in the molecule phosphate, is vital to metabolism, because polyphosphate molecules such as ATP (adenosine triphosphate) are able to store a huge amount of energy in their chemical bonds. Breaking the bond releases its energy; do this enough times in, say, a group of muscle cells, and you can move your arm.

In summary, what you need for life is CHNOPS, plus a dash of salt and a few metals. Of course, those ingredients do have to be in the correct bonding structure, but this seems to occur naturally. Amino acids occur spontaneously, as do sugars and lipids and nucleobases. That's true, at least, on Earth. For the necessary molecular structures to form, a planet must be just the right distance from its sun it can't be too hot or too cold for liquid water to exist. Having an abundant supply of water also helps, because it makes it easier for the ingredients to move around and bump into each other to form interesting compounds. Gravity must be just right, too. Finally, a dash of lightning can provide the much-needed energy to catalyze a reaction that will ultimately lead to the production of the complex molecules amino acids, proteins, fats, carbohydrates, RNA and DNA that lend themselves to producing life.

Living organisms are autonomous, self-propagating chemical systems. They are made from a distinctive and restricted set of small carbon-based molecules that are essentially the same for every living species. Each of these molecules is composed of a small set of atoms linked to each other in a precise configuration through covalent bonds. The main categories are sugars, fatty acids, amino acids, and nucleotides. Sugars are a primary source of chemical energy for cells and can be incorporated into polysaccharides for energy storage. Fatty acids are also important for energy storage, but their most critical function is in the formation of cell membranes. Polymers consisting of amino acids constitute the remarkably diverse and versatile macromolecules known as proteins. Nucleotides play a central part in energy transfer. They are also the subunits from which the informational macromolecules, RNA and DNA, are made.

Most of the dry mass of a cell consists of macromolecules that have been produced as linear polymers of amino acids (proteins) or nucleotides (DNA and RNA), covalently linked to each other in an exact order. The protein molecules and many of the RNAs fold into a unique conformation that depends on their sequence of subunits. This folding process creates unique surfaces, and it depends on a large set of weak interactions produced by noncovalent forces between atoms. These forces are of four types: ionic bonds, hydrogen bonds, van der Waals attractions, and an interaction between nonpolar groups caused by their hydrophobic expulsion from water. The same set of weak forces governs the specific binding of other molecules to macromolecules, making possible the myriad associations between biological molecules that produce the structure and the chemistry of a cell.