BSC 310 Lecture Notes - Lecture 4: Ribose, Amine, Deoxyribose
Organic Compounds
The chemical compounds of living things such as microorganisms are known as organic
compounds because of their association with organisms. The organic compounds, the
subject matter of organic chemistry, are the compounds associated with life processes
in microorganisms.
Carbohydrates.Four major categories of organic compounds are found in all
microorganisms. The first category is the carbohydrates.
Carbohydrates are used by microorganisms as sources of energy. In addition,
carbohydrates serve as structural materials such as in the construction of the microbial
cell wall. Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the
ratio of hydrogen atoms to oxygen atoms is 2:1.
The simple carbohydrates are commonly referred to as sugars. Sugars
are monosaccharides if they are composed of single molecules and disaccharides if
they are composed of two molecules. The most important monosaccharide is glucose, a
carbohydrate with the molecular formula C 6H 12O 6. Glucose is the basic form of fuel for
many species of microorganisms. It is soluble and is transported by body fluids to all
cells, where it is metabolized to release its energy. Glucose is the starting material for
cellular respiration, and it is the main product of photosynthesis in microorganisms.
Three important disaccharides are also found in living things. One disaccharide is
maltose, a combination of two glucose units covalently linked. Yeast cells break down
the maltose from grain starch in the process of alcoholic fermentation. Another
disaccharide is sucrose, the table sugar formed by linking glucose to another
monosaccharide called fructose. A third disaccharide is lactose, composed of glucose
and galactose units. Lactose, the major carbohydrate in milk, is digested to acid by
microorganisms when they sour milk and form sour milk products such as yogurt and ‐
sour cream.
Complex carbohydrates are known as polysaccharides. Polysaccharides are formed
by linking eight or more monosaccharide molecules. Among the most important
polysaccharides are starches, which are composed of hundreds or thousands of
glucose units linked to one another. Starches serve as a storage form for
carbohydrates. Microorganisms break down starch to use the glucose it contains for
their energy needs.
Another important polysaccharide is glycogen, which is related to starch. Many bacteria
have glycogen in thier cytoplasm. Still another is cellulose. Cellulose is also composed
of glucose units, but the units cannot be released from one another except by a few
species of microorganisms, especially those in the stomach of the cow and other
ruminants. The cell walls of algae contain cellulose, and certain fungi have this
polysaccharide. Another polysaccharide called chitin is a primary constituent in the
fungal cell wall.
Lipids. Lipids are organic molecules composed of carbon, hydrogen, and oxygen
atoms. In contrast to carbohydrates, the ratio of hydrogen atoms to oxygen atoms is
much higher. Lipids include steroids, waxes, and the most familiar lipids, fats.
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Fat molecules are composed of a glycerol molecule and one, two, or three molecules
of fatty acids. A fatty acid is a long chain of carbon atoms with associated hydroxyl (–
OH) groups. At one end of the fatty acid is an organic acid (–COOH) group. The fatty
acids in a fat may be all alike or all different. They are bound to the glycerol molecule
during dehydration synthesis, a process that involves the removal of water (Figure ).
The number of carbon atoms in a fatty acid may be as few as four or as many as 24.
Certain fatty acids have one or more double bonds in their molecules. Fats that include
these molecules are called unsaturated fats. Other fatty acids have no double bonds.
Fats that include these fatty acids are called saturated fats.
Some microbial species use fats as energy sources. They produce the enzyme lipase,
which breaks down fats to fatty acids and glycerol. An important type of phosphorus ‐
containing lipid, the phospholipid, is a major constituent of the cell membranes of all
microorganisms.
Proteins. Proteins are among the most complex of all organic compounds. They are
composed of units called amino acids, which contain carbon, hydrogen, oxygen, and
nitrogen atoms. Certain amino acids also have sulfur atoms, phosphorus, or other trace
elements such as iron or copper.
Many proteins are immense and complex as compared to carbohydrates or fats.
However, all are composed of folded, long chains of the relatively simple amino acids.
There are 20 kinds of amino acids, each with an amino (–NH 2) group and an organic
acid (–COOH) group. The amino acids differ with respect to the nature of the chemical
group that is attached to the base structure. Examples of amino acids are alanine,
valine, glutamic acid, tryptophan, tyrosine, and histidine.
Amino acids are linked to form a protein by the removal of water molecules (Figure ).
The links forged between the amino acids are called peptide bonds, and small proteins
are often called peptides.
All living things, including microorganisms, depend upon proteins for their existence.
Proteins are the major molecules from which microorganisms are constructed. Certain
proteins are dissolved or suspended in the watery substance of the cells, while others
are incorporated into various structures of the cells, such as the cell membrane.
Bacterial toxins (metabolic poisons) and microbial flagella and pili are usually composed
of proteins.
An essential use for proteins is in the construction of enzymes. Enzymes catalyze the
chemical reactions that take place within microorganisms. The enzymes are not used
up in the reaction, but remain available to catalyze succeeding reactions. Without
enzymes, the metabolic activity of the microorganism could not take place.
Every species manufactures proteins unique to that species. The information for
synthesizing these unique proteins is found in the nucleus of the cell. The so‐
called genetic code specifies the sequence of amino acids in the protein and thereby
regulates the chemical activity taking place within the cell. Proteins also can serve as a
reserve source of energy for the microorganism. When the amino group is removed
from an amino acid, the resulting compound is energy rich.
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Document Summary
The chemical compounds of living things such as microorganisms are known as organic compounds because of their association with organisms. The organic compounds, the subject matter of organic chemistry, are the compounds associated with life processes in microorganisms. Carbohydrates. four major categories of organic compounds are found in all microorganisms. Carbohydrates are used by microorganisms as sources of energy. In addition, carbohydrates serve as structural materials such as in the construction of the microbial cell wall. Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen atoms is 2:1. The simple carbohydrates are commonly referred to as sugars. Sugars are monosaccharides if they are composed of single molecules and disaccharides if they are composed of two molecules. The most important monosaccharide is glucose, a carbohydrate with the molecular formula c 6h 12o 6. Glucose is the basic form of fuel for many species of microorganisms.
