The sympathetic nervous systemâs fight-or-flight response is your built-in mechanism for safely escaping a life-threatening emergency, such as a lion lurking behind a bush.
The basic building block of DNA is called a NUCLEOTIDE. A nucleotide is made up of one sugar molecule, one phosphate molecule and one of the four bases. Here is the structural formula for the four nucleotides of DNA. Note that the purine bases (adenine and guanine) have a double ring structure while the pyrimidine bases (thymine and cytosine) have only a single ring.
The sugar that is part of a nucleotide is a 5-carbon atom sugar in its ring form. It will either be ribose in RNA or deoxyribose in DNA. It is the ring form of the ribose and deoxyribose that are used in the nucleotide units. Each of the OHs in these molecules serves a particular function.