Editing Biochemical Macromolecules (section)

== 1. Proteins: The Cellular Workhorses ==

Proteins are arguably the most versatile macromolecules in biology, performing almost every functional task in a cell, including catalyzing metabolic reactions (enzymes), providing structural support, and transporting molecules.

* '''Monomer:''' Amino acids. There are 20 standard amino acids, each sharing a common backbone (an amino group and a carboxyl group) but differing in their unique side chain (R-group), which determines their chemical properties.
* '''Polymer:''' Polypeptide chain. Amino acids are linked together by peptide bonds formed through dehydration synthesis.
* '''Structure:''' A protein's function dictates its shape, which folds in four distinct levels:
** ''Primary:'' The linear sequence of amino acids.
** ''Secondary:'' Local folding patterns, primarily alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds.
** ''Tertiary:'' The overall 3D shape of a single polypeptide chain, driven by R-group interactions (e.g., hydrophobic interactions, disulfide bridges).
** ''Quaternary:'' The assembly of multiple polypeptide subunits into a single functional complex (e.g., hemoglobin).