Macromolecules
Slide 2 Macromolecules are large molecules made up of many single units of
similar structure. The single units are called monomers. When several monomers are
connected together during what is called a condensation reaction, a polymer is formed.
These polymers are also referred to as macromolecules. There are four main
macromolecules that are essential to the survival of all forms of life on earth. These are
carbohydrates, proteins, lipids and nucleic acids and together they make up the four
major macromolecules.
Slide 3 The monomers for each of the macromolecules are synthesized by the cell
during regular metabolic functions. Some of the twelve key intermediates that you
learned about earlier provide the chemical structure that these monomers are based on.
(You may want to review lesson 1, module 1).
Slide 4 Regardless of which macromolecule is formed, the combining of
monomers happens in basically the same way. A condensation reaction forms a covalent
bond between monomers and releases water in the process. This type of reaction is also
referred to as dehydration synthesis. The reverse of this reaction can also occur.
Addition of water to a polymer results in the hydrolysis of the molecule, which breaks the
covalent bond between monomers and adds a hydroxyl group to one monomer and a
hydrogen atom to the other monomer. Let’s see how this works for each of the four
major macromolecules.
Slide 5 Carbohydrates consist of sugar monomers called monosaccharides. These
monosaccharides are composed of carbon, oxygen and hydrogen. The carbon skeletons
of monosaccharides range in length from 3 to 7 carbons long, and are often arranged in
ring structures. Focus on the hydroxyl group from one monosaccharide and the hydrogen
atom from the other. These two combine during the condensation reaction to form water.
The covalent bond that creates a carbohydrate polymer is called a glycosidic linkage.
Slide 6 The monomers of proteins are called amino acids. Some of you may have
seen amino acids bottled in natural foods stores as a nutritional supplement. This is
because your body uses available amino acids taken in from the diet and synthesized in
your cells to make proteins, which are essential to the function of all cells. Amino acids
consist of a central carbon atom surrounded by 1), a hydrogen atom, 2), a side chain or R
group, (which we will learn about more later), 3), a carboxyl group, and 4), an amino
group. Focus again on the hydroxyl group of the carboxyl end of the amino acid and the
hydrogen atom connected to the amino group. As you may have guessed, these will
combine to form water during a condensation reaction. This creates a covalent bond
known as a peptide linkage.
