Nucleic acids-Definition, Structure, Properties, Types(DNA, RNA), Nucleotides, FAQs

Any molecule created by a living organism is referred to as a biomolecule. Large macromolecules including proteins, polysaccharides, lipids, and nucleic acids, as well as numerous smaller compounds, are included. Biogenic compounds is a more broad term for this type of chemical.

What are Nucleic Acids ?

Properties of Nucleic Acid

  • Nucleotides are the building blocks of nucleic acid.
  • These make up all living things’ genetic material.
  • In a live cell, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are two forms of nucleic acids.
  • In 1969, Friedrich Miescher discovered both DNA and RNA.
  • A nucleotide is made up of three chemically different components. A heterocyclic base, or nitrogenous base, is one, a monosaccharide pentose sugar is another, and phosphoric acid, or phosphate group, is the third.
  • The nitrogenous bases are made up of one or two heterocyclic rings that include nitrogen atoms. Adenine (A), guanine (G), uracil (U), cytosine (C), and thymine (5-methyl uracil) are the five bases (T).
  • Adenine and guanine are substituted purines with two heterocyclic rings, whereas uracil, cytosine, and thymine are substituted pyrimidines with three heterocyclic rings (1 heterocyclic ring).
  • DNA has the nitrogenous bases A, T, G, and C, whereas RNA has the nitrogenous bases A, U, G, and C.
  • Polynucleotides either include beta-ribose sugar (in RNA) or beta 2′ deoxyribose sugar (in DNA) (in DNA).
  • Nucleosides: Sugar + Base
  • Nucleotides are made up of three parts: base, sugar, and phosphate.
  • The backbone of DNA strands is made up of phosphodiester linkages, which are sugar and phosphate residues.
  • Due to the presence of phosphate groups, they are acidic and negatively charged.

Functions of Nucleic Acids

Structure of Nucleic Acid

The nucleotide is a tiny unitary structure made up of phosphodiester links that connect nucleic acids. Each nucleotide comprises 

  • A Nitrogen base
  • A Pentose sugar
  • Phosphoric acid

An N-glycosidic linkage connects a pentose sugar to a nitrogenous base to form a nucleoside.

  • Nitrogen Bases: The nitrogen bases are the nitrogenous components of the nucleotide. Purine and pyrimidine are two forms of heterocyclic bases that are used to make the five nitrogenous bases.
    • Purines have a two-ring structure. Adenine (A) and guanine (G) are the two purine bases found in DNA and RNA (G).
    • Pyrimidines are bases with only one ring. Cytosine (C) and thymine (T) are the pyrimidine bases found in DNA molecules, while cytosine (C) and uracil are the pyrimidine bases found in RNA molecules (U).
Any molecule created by a living organism is referred to as a biomolecule. Large macromolecules including proteins, polysaccharides, lipids, and nucleic acids, as well as numerous smaller compounds, are included. Biogenic compounds is a more broad term for this type of chemical.
  • Pentose Sugar: Pentose sugar is a sugar molecule or monosaccharide having five carbon atoms. In nucleic acid, the pentose sugar is an aldose sugar. RNA is a nucleic acid that contains ribose sugar, whereas DNA is a nucleic acid that contains a Beta-2’–deoxyribose sugar. Chemically, these two sugars are not the same. Ribose sugar has the chemical formula C5H10O5, whereas Beta-2’–deoxyribose sugar has the molecular formula C5H10O4. With OH groups of 5′ and 3′ carbon, these sugars make bonds with phosphate groups, whereas with nitrogenous bases, they form bonds with OH groups of 1′ carbon.
Any molecule created by a living organism is referred to as a biomolecule. Large macromolecules including proteins, polysaccharides, lipids, and nucleic acids, as well as numerous smaller compounds, are included. Biogenic compounds is a more broad term for this type of chemical.
  • Phosphoric Acid: H3PO4 is the formula. Three reactive -OH groups can be found in phosphoric acid. Two of these are involved in the formation of a sugar-phosphate backbone using phosphodiester bonds.
Any molecule created by a living organism is referred to as a biomolecule. Large macromolecules including proteins, polysaccharides, lipids, and nucleic acids, as well as numerous smaller compounds, are included. Biogenic compounds is a more broad term for this type of chemical.

Bonds between Different Units of Nucleotides

The following types of linkage or bond can be found in a nucleotide unit’s components:

  1. N–glycosidic linkage: To generate a nucleoside, a nitrogenous base is attached to the pentose sugar via a N– glycosidic linkage. Purine nucleosides feature a 1’–9′ glycosidic bond (sugar carbon 1′, A/G nitrogen 9′). The 1’–1′ linkage (sugar carbon 1′ and 1′ nitrogen of T/C) is found in pyrimidine nucleosides.
  2. Phosphoester linkage: A matching nucleotide is generated when a phosphate group is attached to the 5′–OH of a pentose sugar of a nucleoside via phosphodiester linkage. A dinucleotide is made up of two nucleotides joined together by a 3′–5′ phosphodiester bond.

Types of Nucleic Acids

Nucleic acids are of two types:

  1. Deoxyribonucleic acid (DNA)
  2. Ribonucleic Acid (RNA)

DNA 

All living species have DNA as their primary genetic material. It’s a nucleic acid molecule with two strands.

Occurrence: DNA is mostly present in the chromosomes of plant and animal cells’ nuclei. It’s found in mitochondria and chloroplasts as well. It’s found in circular and supercoiled chromosomes in prokaryotes’ cytoplasm. However, it is found in eukaryotes with proteins such as histones and protamine.

Structure: Watson and Crick’s double-stranded double-helical model is the most widely accepted structural model of DNA (1953). The structure of DNA, according to the model, is as follows:

  • A right-handed helical spiral is formed by each chain of DNA, and two chains coil around each other to form a double helix.
  • The phosphodiester bond is the link between the sugar and phosphate molecules, and the bases project inside.
  • The chains run in antiparallel directions, with one strand coming from the 5’→3′ direction and the other coming from the 3’→5′ direction.
  • The nitrogenous bases on one strand form hydrogen bonds with the bases on the other strand. Adenine forms 2H -bonds with thymine (A-T), and guanine forms 3H -bonds with cytosine (G-C). The helical structure is stabilised by this coupling.
  • The chains are complementary because, for every adenine in one chain, there will be thymine in the other; for every guanine in one chain, there will be cytosine in the other, and so on.
  • DNA has a 2nm consistent thickness.
  • The pitch of the helix is 3.4nm for each round of the double helix.
  • Each turn comprises around 10 base pairs. The distance between two neighbouring base pairs is about 0.34 nanometers.
  • The helix’s backbone is made up of sugar and phosphate, with bases aligned along the axis.

RNA

RNA is a single-stranded nucleic acid found in a few viruses, such as retroviruses and viroids, as genetic material.

Occurrence: The majority of RNA is located in the cytoplasm of cells. The nucleolus and nucleoplasm both contain it. Except for a few viruses that have double-stranded RNA, it is generally found as a single-stranded polynucleotide.

Structure: 

  1. The single RNA strand is folded back on itself, generating hairpin-like structures fully or in parts.
  2. In some plant viruses, the genetic material is double-stranded but non-helical RNA.
  3. Each strand of RNA is made up of a large number of ribonucleotides that are bonded together by phosphodiester linkages.
  4. Adenine and uracil (A-U) form a pair, and guanine and cytosine form a pair (G-C).
  5. Messenger RNA, ribosomal RNA, and transfer RNA are the three kinds of RNA.

Difference between DNA and RNA

DNARNA
It contains deoxyribose sugar.It contains ribose sugar.
It can be present in the nucleus, mitochondria, and chloroplast chromosomes.It is related to chromosomes and can be found in the cytoplasm, nucleolus, and nucleoplasm.
Double-stranded structure.Single-stranded structures generally except a few viruses.
Adenine, guanine, cytosine, and thymine are the nitrogenous bases found.Adenine, guanine, cytosine, and uracil are the nitrogenous bases found.
A long molecule with high molecular weight.A relatively short molecule with low molecular weight.
Purines and pyrimidines occur in equal proportionPurines and pyrimidines do not occur in equal proportion.
DNA is the hereditary material.Only a few viruses and viroids have RNA as their genetic material.

Sample Questions(FAQs)

Question 1: What are Nucleic Acids?

Answer:

Nucleic acids are macromolecules that can be found alone or in combination with other chemicals in every live cell. These long strands are formed by the end-to-end polymerization of a large number of nucleotide units coupled by phosphodiester bonds. The term “nucleic acid” refers to a class of large molecules found in cells.

Question 2: What is nucleoside?

Answer:

A nucleoside is formed when a nitrogenous base is connected to a pentose sugar via an N-glycosidic bond.

Question 3: What is a nucleic acid’s primary function?

Answer:

Nucleic acid has the ability to store and transfer genetic information from one generation of cells to the next.

Question 4: What is DNA?

Answer:

The molecule found inside cells that contains the genetic information necessary for an organism’s development and function. This information is handed down through the generations thanks to DNA molecules. Adenine (A) coupled with thymine (T) and guanine (G) paired with cytosine (C) form a double-stranded helix that is kept together by weak hydrogen interactions between purine-pyrimidine nucleotide base pairs (C). Also known as deoxyribonucleic acid (DNA).

Question 5: What is Phosphoester linkage?

Answer:

When a phosphate group is connected to the 5′–OH of a nucleoside’s pentose sugar via phosphoester linkage, a matching nucleotide is formed. A dinucleotide is composed of two nucleotides linked by a 3′–5′ phosphodiester linkage.

Question 6: What is N–glycosidic linkage?

Answer:

A nitrogenous base is connected to the pentose sugar via a N– glycosidic bond to produce a nucleoside. A 1’–9′ glycosidic bond exists between purine nucleosides (sugar carbon 1′, A/G nitrogen 9′). Pyrimidine nucleosides have the 1’–1′ connection (sugar carbon 1′ and 1′ nitrogen of T/C).

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

CBSE Class 12 Chemistry Syllabus Download PDF

Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.

S.NoTitleNo. of PeriodsMarks
1Solutions107
2Electrochemistry129
3Chemical Kinetics107
4d -and f -Block Elements127
5Coordination Compounds127
6Haloalkanes and Haloarenes106
7Alcohols, Phenols and Ethers106
8Aldehydes, Ketones and Carboxylic Acids108
9Amines106
10Biomolecules127
Total70

CBSE Class 12 Chemistry Practical Syllabus along with Marking Scheme

The following is a breakdown of the marks for practical, project work, class records, and viva. The total number of marks for all parts is 15. The marks for both terms are provided in the table below.

Evaluation Scheme for ExaminationMarks
Volumetric Analysis08
Salt Analysis08
Content-Based Experiment06
Project Work and Viva04
Class record and Viva04
Total30

CBSE Class 12 Chemistry Syllabus (Chapter-wise)

Unit -1: Solutions

  • Raoult's law.
  • Colligative properties - relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass.
  • Solutions, Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions.
  • Van't Hoff factor.

Unit -2: Electrochemistry

  • Redox reactions, EMF of a cell, standard electrode potential
  • Nernst equation and its application to chemical cells
  • Relation between Gibbs energy change and EMF of a cell
  • Kohlrausch's Law
  • Electrolysis and law of electrolysis (elementary idea)
  • Dry cell-electrolytic cells and Galvanic cells
  • Conductance in electrolytic solutions, specific and molar conductivity, variations of conductivity with concentration.
  • Lead accumulator
  • Fuel cells

Unit -3: Chemical Kinetics

  • Rate of a reaction (Average and instantaneous)
  • Rate law and specific rate constant
  • Integrated rate equations and half-life (only for zerfirst-order order reactions)
  • Concept of collision theory (elementary idea, no mathematical treatment)
  • Factors affecting rate of reaction: concentration, temperature, catalyst;
  • Order and molecularity of a reaction
  • Activation energy
  • Arrhenius equation

Unit -4: d and f Block Elements  

  • Lanthanoids- Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences.
  • Actinoids- Electronic configuration, oxidation states and comparison with lanthanoids.
  • General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first-row transition metals – metallic character, ionization enthalpy, oxidation states, ionic radii, color, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2Cr2O7 and KMnO4.

Unit -5: Coordination Compounds  

  • Coordination compounds - Introduction, ligands, coordination number, color, magnetic properties and shapes
  • The importance of coordination compounds (in qualitative analysis, extraction of metals and biological system).
  • IUPAC nomenclature of mononuclear coordination compounds.
  • Bonding
  • Werner's theory, VBT, and CFT; structure and stereoisomerism

Unit -6: Haloalkanes and Haloarenes  

  • Haloarenes: Nature of C–X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only). Uses and environmental effects of - dichloromethane, trichloro methane, tetrachloromethane, iodoform, freons, DDT.
  • Haloalkanes: Nomenclature, nature of C–X bond, physical and chemical properties, optical rotation mechanism of substitution reactions.

Unit -7: Alcohols, Phenols and Ethers   

  • Phenols: Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols.
  • Ethers: Nomenclature, methods of preparation, physical and chemical properties, uses.
  • Alcohols: Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, and uses with special reference to methanol and ethanol.

Unit -8: Aldehydes, Ketones and Carboxylic Acids   

  • Carboxylic Acids: Nomenclature, acidic nature, methods of preparation, physical and chemical properties; uses.
  • Aldehydes and Ketones: Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, the reactivity of alpha hydrogen in aldehydes, uses.

Unit -9: Amines    

  • Diazonium salts: Preparation, chemical reactions and importance in synthetic organic chemistry.
  • Amines: Nomenclature, classification, structure, methods of preparation, physical and chemical properties, uses, and identification of primary, secondary and tertiary amines.

Unit -10: Biomolecules     

  • Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins - primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of proteins; enzymes. Hormones - Elementary idea excluding structure.
  • Vitamins - Classification and functions.
  • Carbohydrates - Classification (aldoses and ketoses), monosaccharides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates.
  • Nucleic Acids: DNA and RNA.

The syllabus is divided into three parts: Part A, Part B, and Part C. Part A consist of Basic Concepts of Chemistry, which covers topics such as atomic structure, chemical bonding, states of matter, and thermochemistry. Part B consists of Topics in Physical Chemistry, which includes topics such as chemical kinetics, equilibrium, and electrochemistry. Part C consists of Topics in Organic Chemistry, which covers topics such as alkanes, alkenes, alkynes, and aromatic compounds.

Basic Concepts of Chemistry:

  • Atomic structure: This section covers the fundamental concepts of atomic structure, including the electronic configuration of atoms, the Bohr model of the atom, and the wave nature of matter.
  • Chemical bonding: This section covers the different types of chemical bonds, including ionic, covalent, and metallic bonds, as well as the concept of hybridization.
  • States of the matter: This section covers the three states of matter - solid, liquid, and gas - and the factors that influence their properties.
  • Thermochemistry: This section covers the principles of thermochemistry, including the laws of thermodynamics and the concept of enthalpy.

Chapters in Physical Chemistry:

  • Chemical kinetics: This section covers the study of the rate of chemical reactions and the factors that influence it, including the concentration of reactants, temperature, and the presence of catalysts.
  • Equilibrium: This section covers the principles of chemical equilibrium, including the concept of Le Chatelier's principle and the equilibrium constant.
  • Electrochemistry: This section covers the principles of electrochemistry, including the concept of half-cell reactions, galvanic cells, and electrolysis.

Chapters in Organic Chemistry:

  • Alkanes: This section covers the properties and reactions of alkanes, including their structure, isomerism, and combustion.
  • Alkenes: This section covers the properties and reactions of alkenes, including their structure, isomerism, and addition reactions.
  • Alkynes: This section covers the properties and reactions of alkynes, including their structure, isomerism, and addition reactions.
  • Aromatic compounds: This section covers the properties and reactions of aromatic compounds, including their structure, isomerism, and electrophilic substitution reactions.

In addition to the topics covered in the syllabus, the CBSE Class 12 Chemistry exam also tests students on their analytical and problem-solving skills, as well as their ability to apply the concepts learned in the classroom to real-world situations.

Students can also check out the Tips for the Class 12 Chemistry Exam. They can easily access the Class 12 study material in one place by visiting the CBSE Class 12 page at ANAND CLASSES (A School Of Competitions). Moreover, to get interactive lessons and study videos, download the ANAND CLASSES (A School Of Competitions) App.

Frequently Asked Questions on CBSE Class 12 Chemistry Syllabus

Q1

How many chapters are there in the CBSE Class 12 Chemistry as per the syllabus?

There are 10 chapters in the CBSE Class 12 Chemistry as per Syllabus. Students can learn all these chapters efficiently using the study materials provided at ANAND CLASSES (A School Of Competitions).

Q2

What is the marking scheme for CBSE Class 12 Chemistry practical exam according to the syllabus?

The marking scheme for CBSE Class 12 Chemistry practical exam, according to the syllabus, is 8 marks for volumetric analysis, 8 marks for salt analysis, 6 marks for the content-based experiment, 4 marks for the project and viva and 4 marks for class record and viva.

Q3

Which is the scoring chapter in Chemistry as per CBSE Class 12 syllabus?

The chapter Electrochemistry in Chemistry is the scoring chapter as per CBSE Class 12 syllabus.