are disaccharides. Sucrose contains glucose and fructose. Lactose contains
glucose and galactose.- Polysaccharides. A polysaccharide is comprised of many monosaccharides
and includes glycogen, starch, cellulose, and chitin, which is an amino sugar.
Lipids
Lipidsare our fats and provide protection, insulation and can be used as an
energy reserve. They are important components to the cell membrane and store
pigments.
There are four kinds of lipids. These are:
- Triglycerides. Triglycerides protect and insulate the body from most lipids
and are a source of energy. Because lipids have few polar covalent bonds,
they are mostly insoluble (do not mix well) with polar solvents, like water. - Phospholipids. Phospholipids are a major component in cell membranes.
- Steroids. Steroids are cholesterol and some hormones.
- Eicosanoids. Eicosanoids are divided into two kinds. These are prostaglan-
dinsand leukotrienes. Prostaglandins are involved in various behaviors
such as dilating airways, regulating body temperature, and aiding in the
formation of blood clots. Leukotrienes are involved in inflammatory and
allergic responses.
Other kinds of lipids include fatty acids, lipoproteins and many plant pig-
ments including chlorophyll and beta-carotene and the fat soluble vitamins such
as A, D, E and K.
Proteins
Proteins comprise about 50% of a cell’s dry weight and make up material in the
cell wall. Proteins are peptidoglycans and help to transport chemicals into and
out of a cell. In addition, proteins are part of cell structures and cytoplasmic
components. Some proteins are antibodies that kill bacteria and play a role in
muscle contractions and provide movement of microorganisms. Proteins are
made up of polypeptides that bond together using peptide bonds. There are four
structural levels of proteins. These are:
- Primary. The primary structure is the sequence in which amino acids are
linked to form the polypeptide. Sequences are genetically determined and
even the slightest alteration within the sequence may have a dramatic effect
on the way the protein functions.
CHAPTER 2 Chemical Elements of Microorganisms^41