Problem 68 - Objective Biology for NEET

Question

The bond present between two nucleotides is known as (a) Phosphoester linkage (b) Phosphodiester linkage (c) Glycosidic linkage (d) Peptide linkage

Step-by-Step Solution

Answer

The correct answer is (b) Phosphodiester linkage.

Step 1: Understand the question

The question asks: The bond present between two nucleotides is known as (a) Phosphoester linkage (b) Phosphodiester linkage (c) Glycosidic linkage (d) Peptide linkage

Step 2: Apply Biology knowledge

Using fundamental Biology concepts to analyze the problem.

Step 3: Formulate the answer

The correct answer is (b) Phosphodiester linkage.

Step 4: Conclude

The answer is: The correct answer is (b) Phosphodiester linkage.

Key Concepts

Nucleotides

Nucleotides are the basic building blocks of nucleic acids like DNA and RNA, which are essential for all forms of life. They are comprised of three components: a sugar molecule, a phosphate group, and a nitrogenous base. The sugar can be either ribose, found in RNA, or deoxyribose, present in DNA. The phosphate group is attached to the sugar, and the nitrogenous base (which can be adenine, thymine, guanine, cytosine in DNA, or uracil in place of thymine in RNA) connects to the sugar molecule. The sequence of these nitrogenous bases forms the genetic code that is crucial for protein synthesis and heredity.

Nucleotides not only make up the genetic material of living organisms but they also have roles in energy transfer, as adenosine triphosphate (ATP), and as signalling molecules in various biochemical pathways.

DNA Structure

The structure of DNA is often referred to as a double helix, a term coined after the discovery of its shape by Watson and Crick in 1953. This structure consists of two long strands that twist around each other, comprising a backbone made of sugar and phosphate groups. The sugars in DNA are deoxyriboses. Between the backbones are the nitrogenous bases which pair in a highly specific manner: adenine with thymine, and guanine with cytosine. These pairs are linked by hydrogen bonds and are responsible for the 'steps' you might visualize in a ladder-like structure.

This elegant configuration not only stores genetic information but also allows for DNA replication and repair, processes vital to life. Every time a cell divides, its DNA must be precisely copied to ensure genetic continuity. It is this structure that makes such high-fidelity copying possible.

RNA Structure

RNA, while similar to DNA, differs in several key ways. One of the most distinct differences is the sugar present in RNA nucleotides: ribose. Another notable aspect is that RNA is typically single-stranded as opposed to the double-stranded nature of DNA, although RNA can form complex three-dimensional structures through intramolecular base pairing. Instead of thymine, RNA has uracil, which pairs with adenine.

RNA serves as the direct template for protein synthesis in a process known as translation. It also plays a role in various other cellular processes, such as the regulation of gene expression, through molecules like messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), each having specialized functions in the cell.

Biochemical Bonds

Biochemical bonds are the forces that hold together molecules in the intricate dance of biology. The phosphodiester linkage is the specific bond that connects the nucleotides in both DNA and RNA, forming their respective backbones. This linkage occurs between the 3' carbon atom of one sugar molecule and the 5' carbon atom of the next sugar, creating a continuous chain. It's considered a strong covalent bond, vital for the stability of the nucleic acid structures.

In contrast to the strong covalent bonds within the nucleic acid chains, the hydrogen bonds between nitrogenous bases in DNA are weaker and more easily broken. This difference in bond strengths is critical during processes like DNA replication and transcription, where the strands must separate to allow access to the genetic information they encode.