Understandings:
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Nucleotides are the building blocks of nucleic acids
As you learned earlier in this chapter, nucleic acids are one of the major carbon-based groups. There are three major examples of nucleic acids in nature. They are adenosine triphosphate (ATP), deoxyribonucleic acid (DNA), and ribonucleic acid (RNA). ATP functions as an energy storage compound. Other nucleic acids function as coenzymes. In this section we will focus on DNA and RNA. DNA and RNA are involved with the genetic aspects of the cell.
Both DNA and RNA are polymers of nucleotides. Individual nucleotides are referred to as monomers and always consist of three major parts: one phosphate group, one 5-carbon monosaccharide, and a single nitrogenous base. Chemical bonds occur at specific locations in order to produce a functional unit
the five nitrogenous bases
The base uracil only occurs in RNA, not DNA, and the base thymine only occurs in DNA, not RNA. When drawing nucleotides, it is common practice to put the capitalized first letter of the base inside the rectangle. The sugar differs in the nucleotides of DNA and RNA. DNA nucleotides contain the pentose known as deoxyribose and RNA nucleotides contain ribose
monomers into polymers
Monomers (single nucleotides) in both DNA and RNA may bond together to produce long chains or polymers. each adjoining nucleotide has been drawn in. a different color to emphasize the nucleotide structure.Notice that the chain has an alternating pentose–phosphate backbone, with the nitrogenous bases extending outward. The importance of the order of these nitrogenous bases P will be discussed later in conjunction with the genetic code. The nucleotides attach to one another to form a chain as a result of condensation reactions forming connecting covalent bonds.
singlr strand or double strand
- RNA is composed of a single chain or strand of nucleotides, while DNA consists of two separate chains or strands of nucleotides connected to one another by weak hydrogen bonds. The strands of both DNA and RNA may involve very large numbers of nucleotides.
- For the two strands of DNA, imagine a double-stranded DNA molecule as a ladder . The two sides of the ladder are made up of the phosphate and deoxyribose sugars. The rungs of the ladder (what you step on) are made up of the nitrogenous bases. Because the ladder has two sides, there are two bases making up each rung.
- The two bases making up one rung are said to be complementary to each other. The complementary base pairs are adenine (A)–thymine (T) and cytosine (C)–guanine (G).
Sources :
- Powerpoints shown in class
- Molecular Biology PDF