Biological Molecules: The Carbon Compounds of Life

Vocabulary flashcards covering the key terms, molecular structures, and functions described in Chapter 3 on Biological Molecules.

Organic molecules

Complex molecules based on carbon that form the backbones of biological structures.

Hydrocarbons

Molecules consisting of carbon linked only to hydrogen atoms.

Chemical evolution

The process by which reactions involving inorganic molecules on primordial Earth resulted in organic molecules and the first forms of life.

Functional groups

Small, reactive groups of atoms linked covalently to biological molecules that confer specific chemical properties.

Stereoisomers

Isomers that are mirror images of each other, typically occurring as L-form or D-form, where usually only one form enters biochemical reactions.

Structural isomers

Molecules that share the same chemical formula but have their constituent atoms arranged in different ways.

Dehydration synthesis reaction

A reaction in which components of a water molecule (—H and —OH) are removed to covalently link monomers into polymers.

Hydrolysis

A reaction in which components of a water molecule (—H and —OH) are added to break polymers down into monomers.

Macromolecule

A single polymer molecule with a mass of 1,000 daltons (Da) or more.

Monosaccharides

Carbohydrate monomers containing three to seven carbon atoms that are water-soluble and sweet-tasting.

Disaccharide

A carbohydrate composed of two monosaccharides joined covalently by a dehydration synthesis reaction.

Polysaccharides

Carbohydrate polymers consisting of more than 10 linked monosaccharide monomers.

Neutral lipids

Nonpolar energy-storage molecules with no charged groups, existing as liquid oils or semisolid fats.

Fatty acid

A molecule containing a single hydrocarbon chain with a carboxyl group (—COOH) at one end.

Triglycerides

Neutral lipids formed by dehydration synthesis between a three-carbon glycerol molecule and three fatty acid side chains via ester linkages.

Saturated fatty acid

A fatty acid chain that binds the maximum number of hydrogen atoms and contains only single bonds between carbon atoms.

Unsaturated fatty acid

A fatty acid chain containing one or more double bonds between carbon atoms, introducing kinks in the structure.

Phospholipids

Primary membrane lipids consisting of a glycerol backbone linked to two hydrophobic fatty acid chains and a hydrophilic phosphate group.

Phospholipid bilayer

A film of phospholipids two molecules thick where hydrophilic heads face surrounding water and hydrophobic tails collect in the interior.

Steroids

Lipids characterized by a carbon skeleton framework consisting of four fused rings.

Sterols

The most common steroids, possessing a single polar —OH group at one end of the ring framework and a nonpolar hydrocarbon chain at the other.

Peptide bond

A covalent bond formed by a dehydration synthesis reaction between the amino group of one amino acid and the carboxyl group of another.

Primary structure

The precise, unique sequence in which amino acids are linked in a polypeptide chain.

Secondary structure

The regular structural folding or twisting of an amino acid chain into forms such as an α helix or β strand, stabilized by hydrogen bonds.

Tertiary structure

The overall three-dimensional shape or conformation of a folded protein chain that determines its specific function and solubility.

Quaternary structure

The structural arrangement formed by the association of two or more individual polypeptide chains in a multimeric protein.

Denaturation

The process of unfolding a protein from its active conformation, resulting in the loss of its biological structure and function.

Chaperonins

Guide proteins that temporarily bind to newly synthesized polypeptide chains to direct proper folding into their correct tertiary structure.

Intrinsically Disordered Proteins (IDPs)

Functional proteins or protein regions that lack a fixed three-dimensional structure or remain unfolded.

Nucleotide

The monomer unit of nucleic acids, consisting of a nitrogenous base, a five-carbon sugar, and one to three phosphate groups.

Pyrimidines

Nitrogenous bases containing a single carbon-nitrogen ring, comprising uracil (U), thymine (T), and cytosine (C).

Purines

Nitrogenous bases containing two fused carbon-nitrogen rings, comprising adenine (A) and guanine (G).

Nucleoside

A molecule consisting solely of a nitrogenous base covalently linked to a five-carbon sugar, lacking phosphate groups.

Phosphodiester bond

The covalent linkage connecting adjacent nucleotides in a nucleic acid chain between the 5′ carbon of one sugar and the 3′ carbon of the next via a phosphate group.