Biomolecule Notes

http://www.as.utexas.edu/astronomy/education/spring05/scalo/lectures/309L-2BBiomolA.pdf


Basic Molecules of Terrestrial Self-Replication (brief version)
Theory for origin of life by chemical evolution must explain following:
nuclei--->atoms--->molecules--->monomers--->polymers
It's the last step that is the problem: How to make molecules this complex?
First we’ll list the basic monomers and polymers, and then discuss and show
their properties in more detail.
Monomers are comparatively simple, and include:
amino acids (building blocks of proteins)
and
sugars, phosphates, and bases (building blocks of nucleic acids DNA,RNA)
These are not too difficult to make in the lab, and maybe in space (see the
table of molecules found in the Murchison meteorite), which is what led to overoptimism
about SETI.
Polymers, made from monomers, are much more complex, and their origin is the
basic problem in understanding the origin of life. They include:
carbohydrates (used for food and structural materials)
fats (store and transport energy)
lipids (e.g. cell membranes) – these have a crucial “amphiphilic/amphiphobic”
property due to their structure and that of water.
These are important, especially for life today and probably for the first cells
(which may have predated proteins or nucleic acids). But in terms of getting
complex organisms, the crucial polymers are:
proteins--made by combining 20 (out of thousands!) specific amino acid
monomers. Nearly all have a type of symmetry called "left-handed"
(levo-).
Many functions: enzymes, structure, contraction, gene-regulation, messengers,
defense, transport.
and
nucleic acids--these typically contain anywhere from 105 -- 1010 atoms, so very
long. Made up of 3 types of monomers:
a. sugars--nearly all the ones used in life have "right-handed" symmetry.
(No one knows why.)
b. phosphates
Together, sugars and phosphates make up the sides of the "ladder" of nucleic acids:
S--P--S--P
c. bases--these make up the "rungs" of the "ladder", and carry the code for
reproduction. There are 4 types in DNA:
adenine (A), cytosine (C), guanine (G), and thymine (T) [replaced by
uracil (U) in RNA] [You DON'T have to memorize the names. But do remember
that these bases are used very much like letters that make words and larger
structures of meaning.