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The structure of the DNA molecule: Chemically
and structurally the DNA molecule is one of
the most complex and versatile of molecules, a
necessity in view of all its functions. This versatility
is necessary to provide for all its functions. It
looks like a double helix from the outside (Greek
hélix = spiral) comprising two intertwined spiral
strands. Each strand is a long molecular chain,
and the two strands are essentially parallel, intertwined
in a right-hand spiral. The genetic code
comprises four chemical letters adenine (A), guanine
(G), thymine (T), and cytosine (C). Many
genes do not consist of a continuous piece of
DNA, but are made up like a mosaic of several
separated segments.
In all cells, the genetic information stored in the
DNA molecules controls protein synthesis, and
another nucleic acid, ribonucleic acid (RNA), handles
the transfer of all the information. In general,
all cells of an organism contain identical DNA
molecules, but not all genes are active at the
same time in all the cells.
Proteins: Proteins are the workhorses of life. If
we regard the DNA molecule as the blueprint of
life, then the many different kinds of proteins are
not only the bricks and mortar, they make up the
required tools as well as some of them being the
manual labourers which perform the actual construction
jobs. Our genes provide the conceptual
foundations (they store the “software”), but we
are what we are (the “hardware”) because of our
proteins. Both DNA molecules and proteins consist
of long chains made up of strings of subunits,
but their functions are fundamentally different.
DNA molecules comprise the genetic
archives. On the other hand, proteins exhibit an
unimaginable diversity of three-dimensional
shapes, reflecting their multiplicity of functions.
Some of the tasks of proteins are that they serve
as structural elements for the body, as messenger
molecules, as receptors for messengers, as individual
cell identifiers, and as substances defending
against cells bearing foreign identifiers. Probably
the most important proteins are the
enzymes, which control the rate of biochemical
processes by acting as catalysts. Certain enzymes
can accelerate some reactions a millionfold or
even more. Enzymes are also indispensable for
the actual process of converting genetic information
into its resultant products and processes.
Structure and chemistry of proteins: Although
there are many amino acids, the Creator chose
only 20 of them from which to construct all conceivable
proteins (and thereby the structures)
necessary for life. In the genetic code, three letters
specify one amino acid, and every protein
consists of an exactly determined sequence of
amino acids. All the physical and chemical properties
of an individual protein are determined by
the length of the chain and the specific sequence
of amino acids. The spatial disposition or folding
of the chain is especially important. Proteins fold
in such a way that the free energy is kept to a
minimum; this means that a protein assumes the
most “comfortable” shape. In principle one can
only deduce the three-dimensional structure of
a protein from the amino acid sequence, if all the
forces acting on all of its thousands of atoms are
known, as well as their effects on the surrounding
molecules of the solvent. Such calculations
are impossible in the present state of our knowledge,
even using the most powerful computer
systems ** . But when the Creator made all living
organisms, He constructed each and every protein
in such a way that all the desired properties
were obtained.
* With a possible inherited (maternal) contribution
from the cytoplasmic structure of the egg cell.
** Remarkably, it now appears that the folding of many
proteins after their construction (which would often
be too slow if left to the physical forces acting on a
particular protein’s components) is aided by specially
tailored ”chaperone” molecules.
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