Question

The component present in both nudeotides and nucleosides is (a) sugar (b) phosphate (c) nitrogenous base (d) both (a) and (c).

Short answer

The component present in both nucleotides and nucleosides is both sugar and nitrogenous base, answer (d).

Step-by-step solution

Understanding Nucleotides and Nucleosides

Learn the composition of nucleotides and nucleosides. Nucleotides are composed of a phosphate group, a sugar (pentose), and a nitrogenous base. Nucleosides consist only of a sugar and a nitrogenous base without the phosphate group.

Identify the Common Component

Since nucleosides lack the phosphate group, the common components between nucleotides and nucleosides are the sugar and the nitrogenous base.

Choose the Correct Answer

Based on the common components, the correct answer is the option that includes both sugar and nitrogenous base, which is logically compiled in option (d) both (a) and (c).

Key concepts

Composition of Nucleotides

Nucleotides are the basic building blocks of nucleic acids like DNA and RNA, essential for storing and transmitting genetic information. Each nucleotide is composed of three main parts: a five-carbon sugar molecule, a phosphate group, and a nitrogenous base. The five-carbon sugar can either be ribose, found in RNA, or deoxyribose, which is the sugar component of DNA. These sugars are crucial because they provide the backbone that links together the chain of nucleotides through phosphate groups. The phosphate groups themselves are acidic and connect adjacent sugar molecules. Lastly, the nitrogenous bases—adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U)—are the components that contain genetic instructions and pair specific sequences to encode information.

It's important to remember that the sequence in which these nucleotides are arranged determines the genetic information they carry, much like how letters form words in a sentence.

Composition of Nucleosides

Nucleosides are similar to nucleotides, but they lack one critical component—the phosphate group. They consist of just a five-carbon sugar bonded to a nitrogenous base. In terms of structure, nucleosides can be thought of as the 'halfway' building blocks of nucleic acids. The names of nucleosides differ slightly from that of their corresponding nucleotides; for instance, the nucleoside form of adenine attached to ribose is called adenosine, while guanine linked to ribose is guanosine.

As they lack phosphate groups, nucleosides themselves do not form the backbone of the nucleic acid chain, but they do serve as precursors to the formation of nucleotides which, when phosphorylated, join to form the genetic framework.

Nitrogenous Base

Nitrogenous bases are organic molecules that contain nitrogen and act as the critical subunits of nucleotides; they pair to form the 'rungs' of the nucleic acid 'ladder.' There are two categories of nitrogenous bases found in nucleic acids: purines and pyrimidines. Purines have a double-ring structure and include adenine (A) and guanine (G). Pyrimidines, on the other hand, have a single-ring structure and include cytosine (C), thymine (T), and uracil (U).

In DNA, adenine pairs with thymine and guanine pairs with cytosine, whereas in RNA, uracil takes the place of thymine. This pairing is governed by hydrogen bonding, which is crucial for the stability of the DNA double helix and for accurate replication and transcription of genetic material.

Phosphate Group

The phosphate group in a nucleotide is a key component that distinguishes nucleotides from nucleosides. It consists of one phosphorus atom surrounded by four oxygen atoms, forming a tetrahedral shape. This group carries a negative charge, which contributes to the overall polarity of the nucleotide. In nucleic acids, the phosphate groups provide the connecting points between the sugar of one nucleotide and the sugar of another, forming a 'backbone' of alternating sugar and phosphate attachments.

These phosphodiester bonds are what give strength to the structure of nucleic acids and enable the creation of long chains of nucleotides that make up the strands of DNA and RNA. Without the phosphate group, the individual nucleosides cannot link together to form the polymers necessary for life.

Sugar in Nucleic Acids

The sugar component in nucleic acids is either a ribose (in RNA) or deoxyribose (in DNA), and it plays a fundamental role in the structure of nucleotides. In ribose, the sugar contains five carbons and all corresponding hydroxyl (-OH) groups. In contrast, deoxyribose, as the name implies, lacks one oxygen atom ('deoxy-' meaning without oxygen) on the second carbon in the ring.

This difference may seem small, but it has a significant effect on the structure and properties of the nucleic acid; for example, deoxyribose makes DNA more stable, allowing it to store genetic information long-term, while the presence of one more -OH group in ribose gives RNA the flexibility to assist in various functions such as protein synthesis and gene regulation.