Question

Go to Figure 5.23a and, for the top three nucleotides, number all the carbons in the sugars, circle the nitrogenous bases, and star the phosphates.

Short answer

Nucleic acids are a sort of macromolecule found in all living things. These are the information storage devices of cells that make up an organism's genetic makeup and transport information.

All life on earth uses nucleic acids for the storage of genetic information except for viruses. RNA (Ribonucleic acid) and DNA (Deoxyribonucleic acid) are the two types of nucleic acids.

Step-by-step solution

Nucleic acids 

Nucleic acids are a sort of macromolecule found in all living things. These are the information storage devices of cells that make up an organism's genetic makeup and transport information.

All life on earth uses nucleic acids for the storage of genetic information except for viruses. RNA (Ribonucleic acid) and DNA (Deoxyribonucleic acid) are the two types of nucleic acids.

Nucleotides are the building blocks of nucleic acids

Each nucleotide consists of three components: a phosphate group, a pentose sugar, and a nitrogen base.

In RNA, the pentose sugar is D-ribose, while in DNA, it is 2-deoxy-D-ribose. Purine and pyrimidine are the two classes of nitrogen bases present in nucleic acids. Thymine, uracil, and cytosine are the three pyrimidines bases, whereas adenine and guanine are the two purine bases that are present in nucleic acids.

In nucleotides, the nitrogen base is attached to position 1'C of sugar through the β-N-glycosidic bond, and the phosphate group connects to the 5'C of the sugar moiety.

Sugar-phosphate backbone of nucleic acids

Nucleic acids are strands of nucleotides that are linked by a phosphodiester bond. The phosphate group of one nucleotide forms a covalent bond with the 3'C of the pentose sugar of the adjacent nucleotide. This leads to the formation of the sugar-phosphate backbone with alternating sugar-phosphate units.

The carbon atoms in the pentose sugar ring can be numbered clockwise, starting with a carbon atom adjacent to the ring oxygen atom.

Thus, a large number of nucleotides form the polynucleotide that comprises the strands of nucleic acids.