Molecules to Metabolism: Carbon Compounds in Life

Posted on Mar 6, 2025 in Chemistry

Molecules to Metabolism

Molecular biology explains living processes in terms of the chemical substances involved.

It involves explaining biological processes from the structures of the molecules and how they interact with each other.
Many molecules are important to living organisms, including water, carbohydrates, lipids, proteins, and nucleic acids.
Proteins are one of the most varied macromolecules, performing many cellular functions, including catalyzing metabolic reactions (enzymes).
The relationship between genes and proteins is also important.
Molecular biologists break down biochemical processes into their component parts (reductionism).
When they look at the sum of all these reactions as a whole, they can study the emergent properties of that system.

Urea is an example of a compound that is produced by living organisms but can also be artificially synthesized.

Urea is a component of urine which is produced when there is an excess of amino acids in the body; it’s a way to secrete nitrogen.
A series of enzyme-catalyzed reactions produce urea in the liver, where it is transported by the blood to the kidney, where it is filtered out and excreted in the urine.
Urea can be produced artificially through different chemical reactions; however, the product is the same.
Urea is mainly used as a nitrogen source in fertilizers.

Carbon atoms can form four covalent bonds, allowing a diversity of stable compounds to exist.

Carbon has a few unique bonding properties – the most important of which is its ability to form long chains of carbon. No other element can bond like carbon does.
The reason carbon can do this is that carbon-carbon bonds are extremely strong. This allows carbon to make up many of the basic building blocks of life (fats, sugars, etc.).
Since carbon-carbon bonds are strong and stable, carbon can form an almost infinite number of compounds.
In fact, there are more known carbon-containing compounds than all the compounds of the other chemical elements combined, except those of hydrogen (because almost all organic compounds contain hydrogen too).
Carbon can also form rings, e.g., glucose.
The simplest form of an organic molecule is the hydrocarbon—a large family of organic molecules that are composed of hydrogen atoms bonded to a chain of carbon atoms, e.g., Methane.
All bonding in hydrocarbons is covalent.
Covalent Bonds are chemical bonds formed by the sharing of a pair of electrons between atoms. The nuclei of two different atoms are attracting the same electrons.
Carbon can form single, double, and triple bonds.
Carbon has 4 valence electrons in its outer shell.

Life is based on carbon compounds, including carbohydrates, lipids, proteins, and nucleic acids.

Lipids are compounds that are insoluble in water but soluble in nonpolar solvents.
Some lipids function in long-term energy storage. Animal fat is a lipid that has six times more energy per gram than carbohydrates.
Lipids are also an important component of cell membranes.
Some examples of lipids are triglycerides, steroids, waxes, and phospholipids.
Animal fats (saturated) are solid at room temperature, and plant fats (unsaturated) are liquid at room temperature.

Proteins are composed of one or more chains of amino acids.
All proteins are composed of carbon, hydrogen, oxygen, and nitrogen.
Proteins are distinguished by their “R” groups. Some of these also contain sulfur.

Nucleic acids are composed of smaller units called nucleotides, which are linked together to form a larger molecule (nucleic acid).
Each nucleotide contains a base, a sugar, and a phosphate group. The sugar is deoxyribose (DNA) or ribose (RNA). The bases of DNA are adenine, guanine, cytosine, and thymine. Uracil substitutes for Thymine in RNA.
They are made from carbon, hydrogen, oxygen, nitrogen, and phosphorus.