Chapter 2 Module 3 Organic Molecules (continued)

Chapter 2 Module 3 Organic Molecules (continued)


This is a continuation
of Chapter 2 Module 3, Organic Molecules. We will start with
nucleic acids. Nucleic acids are the last
type of organic molecule we will study. Nucleic acids are large
organic molecules found in the nucleus of the cell. They store and process
information for the cells. Two types of
nucleic acids exist, the DNA, or
deoxyribonucleic acid, and RNA, or ribonucleic acid. The role of DNA is to determine
inherited characteristics such as hair color, skin
color, or even how well one metabolizes medications. DNA also directs
protein synthesis, controls enzyme production,
and controls metabolism. RNA, on the other hand,
controls intermediate steps in protein synthesis that
you will learn more about in upcoming modules. Structurally, both DNA and RNA
are strings of nucleotides. A nucleotide has three molecular
parts, a pentose sugar, either deoxyribose for
DNA or ribose for RNA, a phosphate group, and
a nitrogenous base that is either adenine or A, guanine
or G, thymine or T, cytosine or C, and uracil, or U.
Cytosine, thymine, and uracil are considered pyrimidines
and adenine and guanine are considered purines. Thymine will only be
found on DNA molecules and uracil will only be
found on RNA molecules. The nucleic acid strands are
long chains of nucleotides. Each nucleotide
contains one base. These nucleotides are linked
through the phosphate group on one nucleotide to the sugar
group on another nucleotide through the process of
dehydration synthesis. When several to thousands
of these nucleotides are linked together, it makes
one strand of nucleic acid. In DNA, two of these
nucleic acid strands will be linked together by
their bases with hydrogen bonds. Then, these two strands
that are linked together form a twisting double
helix formation. When the nucleotides
of one strand link to the nucleotides
of the other strand, the bases that link together
are called a complementary pair. The purines will link
to the pyramidines, so that adenine and guanine will
link with thymine and cytosine, respectively. In other words, adenine
will only link to thymine and guanine will only
link to cytosine in DNA. DNA always has more than
45 million nucleotides in one molecule. DNA will store information
that controls protein synthesis or, in other words,
controls what, when, and how many proteins
the cell will make. RNA is similar to DNA with
some important differences. First, RNA consists of only one
strand of nucleic acids, which means there is only one strand
of nucleotides linked together through dehydration synthesis. The other difference
is that thymine is not one of the bases on RNA. Uracil takes the place of
thymine on an RNA molecule. And lastly, the sugar
in the nucleotide is a ribose sugar and
not a deoxyribose sugar. RNA may have anywhere between
just a few nucleotides to up to about 50,000
nucleotides in its strand. There are three
types of RNA we will study, messenger RNA or
mRNA, transfer RNA or tRNA, and ribosomal RNA or rRNA. RNA performs protein synthesis
as directed by the DNA. We will talk more
about DNA and RNA in the modules
regarding the cell. Other than their
use in DNA and RNA, nucleotides can also be
used to store energy. Adenosine diphosphate
or ADP is a nucleotide that contains the
base adenine as well as two phosphate groups. The “di” in the
word “diphosphate” tells you there are
two phosphate groups. When a third phosphate
group is added to ADP by using a high-energy
bond to do so, the new molecule formed is
adenosine triphosphate or ATP. Adding this phosphate group to
ADP is called phosphorylation. ATP is a high-energy
compound that is basically storing energy in
that high-energy bond between the last two
phosphate groups. When energy is
needed in the body, the phosphate group
will break off and release the
energy, which can then be used for whatever functions
in the body require energy. We will learn more
about energy usage in the body in a later module. This ends Chapter 2 Module
3, Organic Molecules.

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