DNA and Proteins
DNA was discovered as a major chemical of the
nucleus at about the same Mendel and Darwin their
work. However, during the early 1900s, protein
was considered better candidates as molecules
able to transmit large amounts of hereditary information
from generation togeneration.
Although DNA was
know to be a very large molecule, it seemed likely
that its 4 chemical components were assembled
in a monotonous pattern-like a synthetic polyme.
Also, no specific cellular function had yet been
found for DNA. Proteins, on the other hand, were
important as enzymes and structural components
of living cells. Proteins were also known to be
polymers of numerous amino acids. These polymers
are called polypeptides.
Most importantly, the
20 amino acid "alphabet" of proteins
potentially could be configured into more unique
information-carrying structures than the 4-letter
alphabet of DNA.
Most people know that muscles are mainly built
up by proteins. But that is just one of many tasks
proteins have in our body. In fact, everything
we do - think, laugh and run - emerges from the
coordinated activities of a lively, intercommunicating
society of protein molecules.
Proteins are the building
blocks of all cells and execute nearly all cell
functions. The multiplicity of functions performed
by proteins arises, from the huge number of different
three-dimensional shapes they adopt.
proteins are polymers of amino acids, joined together
by peptide bonds in a long chain, also called a
polypeptide chain. Some proteins consist of more
than one polypeptide chain and they frequently associate
with each other to form larger protein complexes.
Human proteins are composed of only 20 different
kinds of amino acids, ten of which our body can
produce by itself (non essential amino acids)
and ten that must be provided through food (essential
Each type of protein has its own
unique sequence of amino acids; this sequence,
known as its primary structure, actually determines
the shape (secondary and tertiary structure) and
function of the protein.