Carbon and the Backbone of Life

A set of vocabulary flashcards covering key concepts about carbon’s role in biology, its bonding, and the structure of organic molecules.

Carbon backbone

The central framework of organic molecules formed by carbon chains that can vary in length and branching, enabling diverse structures.

Organic molecule

A molecule that contains carbon and is the building block of living matter.

CHON

The four most common elements in living matter: carbon (C), hydrogen (H), oxygen (O), and nitrogen (N); together they make up about 90% of life’s mass.

Sulfur and phosphorus

Two additional essential elements present in living organisms; used in various biological molecules and processes; abundances are fairly uniform across organisms.

Valence

The number of covalent bonds an atom can form, equal to the number of unpaired electrons in its outer shell.

Carbon valence

Carbon has valence four, allowing it to form four covalent bonds with other atoms and enabling vast molecular diversity.

Hydrogen valence

Hydrogen has valence 1; it forms one covalent bond.

Oxygen valence

Oxygen has valence 2; it can form two covalent bonds.

Nitrogen valence

Nitrogen has valence 3; it can form three covalent bonds.

Carbon dioxide (CO2)

A gas exhaled by living beings; carbon is double-bonded to two oxygens, with each atom achieving a full outer shell.

Methane (CH4)

The simplest alkane: one carbon bound to four hydrogens; tetrahedral structure.

Ethane (C2H6)

Two carbons connected by a single bond; each carbon bonded to hydrogens; an example of a saturated hydrocarbon with a distinct 3D shape from methane.

Ethylene (C2H4)

Two carbons connected by a double bond; an unsaturated hydrocarbon with a different structure and properties from methane and ethane.

Carbon skeleton

Chains of carbon atoms that form the backbone of most carbon-containing molecules; can vary in length and branching.

Linear vs branched carbon chains

Carbon chains can be linear or branched, leading to different compounds (e.g., butane with four carbons in a chain; branching yields isomers).