Page 77 - The Origin of Life and the Universe - International Conference 2016

The Origin of Life and the Universe

- 1 of collagen, by permitting the chains comprising
the protein to bind tightly together, which in-
: % % 7 creases the resistance of the collagen fibers.
7 ! Collagen fibers have been determined to have
greater tensile strength than steel. If another
side-chain amino acid were used in place of
In theory, one would expect the number of glycine, the resulting collagen fibers could not
amino acids in nature to be far more than 200. possess the same level of tensile strength. At
Even in human body, many amino acids not the same time, were it not for glycine, the
used in human proteins are used in the body's collagen fibers would also lack enough strength
metabolic functions. Why, therefore, do proteins to bind cells to one another.
select only 20 amino acids when so many are As you can see from this brief description,
more available? there is a consciousness and planning behind
We can answer this question by examining the selection of these 20 specific amino acids
proteins' functions and structures. In order to from among the 200 occurring naturally. Had
perform their functions essential to life, proteins this selection taken place at random, then the
need to possess specific features, and amino proteins necessary for life could never have
acids are one of the main elements that give formed. If only a single amino acid were any
them those properties. For instance, it is essential different from how it needs to be, a vital function
that an amino acid possess hydrophobic (or would collapse, and life would therefore become
water-repellent) side chains. But these side impossible. It is apparent that there are conscious
chains must not be very large, or else it will be systems, rational selection, and order in every
impossible to pack and install them inside the phase of life.
proteins.
Side chains must also possess two features
known as helix and layered formations. As a
result of these, a protein can assume a three-
dimensional form, and these are also essential
for the protein to work properly.
Research has shown that of the 20 amino
acids used in proteins, most are hydrophobic
side chains. Half possess a-helix properties
and the other half, b-layer properties.
Examine the properties of these 20 amino
acids one by one, and you can understand why
they have been specially selected for proteins. 1. Pro
For instance, even glycine—the smallest and 2. Gly
simplest amino acid—has a very important role
to play in collagen, which is one of the most im-
The amino acid structure of the protein collagen is
portant proteins. If the three amino acids that seen. As you see, one of each three amino acids is
comprise collagen, one is glycine. Its small di- glycine (Gly). Being very small, glycine is the most
suitable amino acid for the structure of collagen.
mensions play an important role in the structure

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