Download Macromolecules

Macromolecules
Macromolecules are giants of the atomic world. The prefix “macro-”
means "very large scale." Indeed, macromolecules dwarf other
molecules involved in life’s chemistry, such as table salt (NaCl) or water
(H2O). Macromolecules are typically comprised of at least 1,000 atoms,
with repeated structures of smaller components. The process of
polymerization links together the smaller components (monomers). It’s
the extent of repetition that leads to large size.
It’s the large size of macromolecules that dictates their importance in
living systems. They are the basis of complex cellular life.
Macromolecules are not intrinsically stable. They are not created in the
absence of life, nor can they persist for long outside living systems.
Essentially, a macromolecule is a single molecule that consists of many
covalently linked subunit molecules. A polymer is a single molecule
composed of similar monomers. In physiology, the four major
macromolecules are:
1. Nucleic acids - made of nucleotide subunits linked through their
phosphate backbone.
2. Proteins - made of amino acid subunits linked between carbon and
nitrogen.
3. Lipids - typically large molecules comprised of nonpolar bonds,
making them hydrophobic. Some lipids contain covalently attached
polar groups, which may act as attachment points for multiple
hydrophobic lipid molecules.
4. Carbohydrates - have covalently linked sugar groups.
So far, we have discussed the major elements and types of bonds that
are important in the functioning of a cell. Together these elements and
bonds define the major properties of the four classes of macromolecules
that make up a cell: carbohydrates, proteins, lipids and nucleic acids. In
this module, we will explore these macromolecules.
Carbohydrates, proteins and nucleic acids are all examples of
polymers. Polymers are very large molecules composed of smaller
units joined by covalent bonds using a common set of chemical
reactions. Proteins are linear polymers of amino acids all joined by
peptide bonds. Polysaccharides are the carbohydrates joined through
glycosidic bonds in sometimes quite complex branched structures. DNA
and RNA are polymers of nucleic acids linked by phosphodiester bonds.
This module includes a discussion of the structures of these organic
macromolecules.