Organisms and Environmental Factors 13
in very small amounts in biological functions, as trace elements. The most
important are: F, Si, V, Cr, Mn, Fe, Co, Cu, Zn, Se, Mo, Sn, I; an empirical
formula gives the average occurrence of the six main elements in the composition of living matter: H 2960 O 1480 C 1480 N 16 P 1.8 S. Significant deviations
from this formula have been observed in the organic matter of the various
categories of organisms.
The organic substances formed from the above-mentioned chemical
elements may be divided into four main classes of polymeric compounds:
polysaccharides, lipids, proteins and nucleic acids.
Polysaccharides are polymeric carbohydrates having the formula (CH 2 O)n
with n > 3. They hydrolyse with ease or difficulty into simple carbo hydrates
(monosaccharides). Starch and cellulose are basic polysaccharides. Starch
is easily hydrolysed and is used as food by many organisms. Cellulose is
the most abundant organic compound on the planet, but most organisms,
including humans, cannot hydrolyse it. Certain organisms do have this
ability, among them cows and termites, which have the right sort of bacteria
in their peptic system. Wood and cotton are examples of materials that are
rich in cellulose.
Lipids include fats, oils and in general organic compounds that are soluble in organic solvents (e.g. benzine or ether) but are virtually insoluble in
water. Fats and oils consist of C, H, and O, are more or less easily hydrolysed in organic acids and glycerine, and their biological role consists of
storing combustible material. The lipids also include the lipoids, which may
contain P or N.
Proteins are polymeric compounds, usually of great complexity, with
high molecular weight (even over 1,000,000). They contain C, O, H and
N in average proportions by weight: 50%, 23%, 7% and 16% respectively.
S is also present in almost all the proteins, in a proportion of up to 3%.
Proteins take part in most biological functions, e.g. as catalysts (enzymes)
in biochemical reactions, as structural elements of cells and as transporters
of matter (e.g. transport of oxygen to the cells by haemoglobin).
The nucleic acids are extremely complex compounds composed of hundreds to thousands of nucleotides. Depending on the carbohydrate that
constitutes their base, we can divide them into DNA (deoxyribonucleic
acid) and RNA (ribonucleic acid). They are spiral shaped, forming a double
or single helix. DNA plays a crucial biological role, since it contains the
chromo somes with genetic information on the structure and functioning of every organism. When a cell divides, each daughter cell has a full
copy of the DNA of its parent cell, where all the hereditary information is
recorded. RNA transports the information stored in the DNA to various
parts of the cell, and in some organisms it is also involved in preserving
genetic information.
in very small amounts in biological functions, as trace elements. The most
important are: F, Si, V, Cr, Mn, Fe, Co, Cu, Zn, Se, Mo, Sn, I; an empirical
formula gives the average occurrence of the six main elements in the composition of living matter: H 2960 O 1480 C 1480 N 16 P 1.8 S. Significant deviations
from this formula have been observed in the organic matter of the various
categories of organisms.
The organic substances formed from the above-mentioned chemical
elements may be divided into four main classes of polymeric compounds:
polysaccharides, lipids, proteins and nucleic acids.
Polysaccharides are polymeric carbohydrates having the formula (CH 2 O)n
with n > 3. They hydrolyse with ease or difficulty into simple carbo hydrates
(monosaccharides). Starch and cellulose are basic polysaccharides. Starch
is easily hydrolysed and is used as food by many organisms. Cellulose is
the most abundant organic compound on the planet, but most organisms,
including humans, cannot hydrolyse it. Certain organisms do have this
ability, among them cows and termites, which have the right sort of bacteria
in their peptic system. Wood and cotton are examples of materials that are
rich in cellulose.
Lipids include fats, oils and in general organic compounds that are soluble in organic solvents (e.g. benzine or ether) but are virtually insoluble in
water. Fats and oils consist of C, H, and O, are more or less easily hydrolysed in organic acids and glycerine, and their biological role consists of
storing combustible material. The lipids also include the lipoids, which may
contain P or N.
Proteins are polymeric compounds, usually of great complexity, with
high molecular weight (even over 1,000,000). They contain C, O, H and
N in average proportions by weight: 50%, 23%, 7% and 16% respectively.
S is also present in almost all the proteins, in a proportion of up to 3%.
Proteins take part in most biological functions, e.g. as catalysts (enzymes)
in biochemical reactions, as structural elements of cells and as transporters
of matter (e.g. transport of oxygen to the cells by haemoglobin).
The nucleic acids are extremely complex compounds composed of hundreds to thousands of nucleotides. Depending on the carbohydrate that
constitutes their base, we can divide them into DNA (deoxyribonucleic
acid) and RNA (ribonucleic acid). They are spiral shaped, forming a double
or single helix. DNA plays a crucial biological role, since it contains the
chromo somes with genetic information on the structure and functioning of every organism. When a cell divides, each daughter cell has a full
copy of the DNA of its parent cell, where all the hereditary information is
recorded. RNA transports the information stored in the DNA to various
parts of the cell, and in some organisms it is also involved in preserving
genetic information.