Question

Adenosine, guanosine, thymidine, uridine, cytidine are all butadenylicacid, guanylicacid, uridylicacid, cytidylic acid are (a) nucleotides, nucleosides (b) nucleosides, nucleotides (c) nucleotides, nucleic acids (d) nucleosides, nucleic acids

Short answer

The correct answer is (b) nucleosides, nucleotides.

Step-by-step solution

Define Nucleosides and Nucleotides

Nucleosides are molecules consisting of a nitrogenous base (adenine, guanine, thymine, uracil or cytosine) bonded to a sugar molecule. Nucleotides are nucleosides with one or more phosphate groups attached to the sugar.

Identify Nucleosides and Nucleotides from the list

Adenosine, guanosine, thymidine, uridine, cytidine lack phosphate groups and are therefore nucleosides. Adenylic acid, guanylic acid, uridylic acid, cytidylic acid have phosphate groups and are thus nucleotides.

Key concepts

Nitrogenous Bases

At the core of nucleic acids are nitrogenous bases, which are essential components of the genetic code. These bases include adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U). Adenine and guanine are classified as purines, which have a double-ring structure. Cytosine, thymine, and uracil are pyrimidines, characterized by a single-ring structure.

Nitrogenous bases form hydrogen bonds with one another, adhering to specific pairing rules: adenine pairs with thymine in DNA, and with uracil in RNA; guanine pairs with cytosine. This pairing is crucial for the double helix structure of DNA and the stability of RNA molecules. The sequence of these nitrogenous bases along a nucleic acid strand serves as a template for encoding proteins, hence playing a pivotal role in the storage and transmission of genetic information.

Phosphate Groups

Phosphate groups are integral to the structure of nucleotides, which are the building blocks of nucleic acids. A phosphate group is made up of one phosphorus atom surrounded by four oxygen atoms. In the structure of a nucleotide, the phosphate group is bonded to the 5' carbon of the sugar molecule, which can be either ribose in RNA or deoxyribose in DNA.

In nucleic acids, these phosphate groups link adjacent nucleotides together through phosphodiester bonds. These bonds are formed between the 3' hydroxyl group of one sugar and the 5' phosphate of the next sugar. This connection creates the sugar-phosphate backbone of nucleic acids, providing structural support and forming the 'ladder' on which the nitrogenous bases are attached. The presence or absence of phosphate groups thus distinguishes nucleotides from nucleosides, with the former having one or more phosphate groups.

Nucleic Acids

Nucleic acids, primarily DNA and RNA, are polymers composed of long chains of nucleotides, which serve as the blueprint for life. DNA (deoxyribonucleic acid) carries the genetic instructions for the development and functioning of living organisms. RNA (ribonucleic acid), meanwhile, is involved in various biological roles, including coding, decoding, regulation, and expression of genes.

Both DNA and RNA are made by linking nucleotides together through phosphodiester bonds, creating a sugar-phosphate backbone with nitrogenous bases protruding from it. The sequence of nitrogenous bases along the nucleic acid polymer constitutes the genetic information. During cell division, DNA replicates, ensuring that genetic information is passed on to the next generation. RNA, on the other hand, is primarily involved in the synthesis of proteins, carrying out the instructions encoded in DNA to produce the necessary proteins for life processes.