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The fourth group of biomolecules are the nucleic acids. Nucleic acids are made of carbon, hydrogen, oxygen, nitrogen and phosphorous atoms. Nucleic acids store and transfer cellular information and transfer energy in all living organisms. Nucleic acids are made of small repeating units or building blocks called nucleotides. Nucleotides consist of three parts, a 5-carbon sugar, a nitrogenous base, and a phosphate group. Nuclotides are linked together when a bond forms between the phosphate group on one nucleotide and the sugar group on another nucleotide.
There are two types of nucleic acids found in living organisms. Deoxyribonucleic acid (abbreviated DNA) and ribonucleic acid (abbreviated RNA). DNA stores hereditary information in small segments called genes inside long chains. RNA delivers gene information from DNA to create protein. Other RNA molecules are active, molecules that regulate and help chemical reactions occur inside cells. An enormous body of evidence suggests that RNA was the original molecule of life due to RNA’s ability to both store hereditary information and regulate chemical reactions in organisms.
One difference between DNA and RNA are in the sugars that make up their nucleotides. Only two 5-carbon sugars are found in nature: ribose and deoxyribose. Deoxyribose is a ribose derivative in which an oxygen atom is missing from one carbon; the carbon was deoxygenated. DNA contains deoxyribose sugars in their nucleotides while RNA contains ribose sugar in the nucleotides. By having one less oxygen this makes DNA more stable than RNA.
Another differnce in between DNA and RNA is the nucleotides that bond together. DNA and RNA are both composed of only 4 nucleotides. Adenine, cytosine, and guanine make up both DNA and RNA. The difference occurs in the fourth nucleotide. In DNA, this nucleotide is thymine but in RNA it is replaced by the nucleotide uracil. The sugar and phosphate groups are identical (except for the oxygen on the sugars), the part of the nucleotide that is different is the nitrogenous base.
DNA and RNA also look different structually. DNA when assmebled forms a two-stranded molecule whereas RNA forms just a single stranded molecule. In DNA, the bases on the nucleotides pair up other bases form the other strand. Adenine bases will only pair with thymine bases (A & T) and Cytosine bases willonly pair with guanine bases (C & G). Although RNA is not double stranded, within cells different strands of RNA will often pair up in the process of constructing proteins. Just like in DNA cytosine and guanine pair up but adenine pairs up with uracil.
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