Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter Biomolecules. This page offers a step-by-step solution to the specific question from Exercise 2, Question 23: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.
The two strands in DNA are not identical but are complementary. Explain.
DNA is a long polymer of deoxyribonucleotide. The chemical structure of nucleotides has three components. Nitrogenous bases, pentose sugar and a phosphate group. There are two types of Nitrogenous bases: purine and pyrimidines. Purines are Adenine (A) and Guanine (G) and Pyrimidine are Cytosine (C), Uracil (U) and Thymine (T). Out of these nitrogenous bases only 4 are present in DNA and RNA, In DNA Adenine is paired with Thymine by double hydrogen bond (A=T) whereas cytosine is coupled with Guanine by triple hydrogen bond (C=G, G=C). These nitrogenous bases are linked with pentose sugar through N-glycosidic linkage and form a structure called nucleoside.
Nucleoside when linked with (PO4) phosphate group through phosphodiester linkage. Combination of nucleotides with phosphate groups form the basic unit of nucleic acid called nucleotides. These nucleotides are linked together through phosphodiester bonds to form a long chain or backbone of DNA double helical structure. DNA was first identified by Friedrich Meischer in 1865 whereas its double helical structure was revealed by James watson and Francis crick. The base pairing confers a very unique property of the polynucleotide chain: each strand of DNA is complementary to each other. Therefore the sequence of bases in one strand is known then the sequence in other DNA can be determined with a template or mother strand that synthesizes the new daughter strand the process is known as DNA replication. This process requires a set of enzymes that catalyses the reaction. The double helical structure unwinds and forms a fork-like structure known as a replication fork. The DNA polymerase catalyses the polymerisahy only in one direction, that is 5’-3’. From two DNA strands which have polarity of 3’-5' act as mother or template stanels and new strand synthesis in opposite polarity of 5’-3’. Lets understand through this example:
As we know double hydrogen (Adenine) A=T (Thymine),
(Cytosine) C=G (Guanine) two DNA strand are said to be complementary to each other.
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
| Experiment |
A/ mol L - 1 |
B/ mol L - 1 |
Initial rate/mol L - 1 min - 1 |
| I | 0.1 | 0.1 |
2.0 × 10 - 2 |
| II | -- | 0.2 |
4.0 × 10 - 2 |
| III | 0.4 | 0.4 | -- |
| IV | -- | 0.2 |
2.0 × 10 - 2 |
NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:
Stay updated with our latest educational content and study tips
One of the challenging things students face nowadays is procrastination. It hinders productivity, making it difficult for students to score well. We often associate procrastination as just being lazy. But there’s more to it. Various studies have shown that procrastination stems from negative feelings such as stress and anxiety. Oftentimes, when we start, we think […]
Read MoreThe CBSE Board Exam is a crucial milestone for millions of students across India. The Central Board of Secondary Education is famous for its imparting quality education and knowledge which reaches out to a large share of students. Also, it is important to know that, the CBSE board takes a slight unconventional route, since it […]
Read MoreHaryana government issued a notification on 31st December 2024 through its Gazette notification No. 42/119/2019-5HR-II for CET Haryana 2024. The Common Eligibility Test (CET) for Haryana is a significant opportunity for candidates seeking government jobs in Group C and Group D posts. Below is a comprehensive summary of the key information you need to know […]
Read MoreSacrificing your sleep to study more is doing more damage than you think. While it may seem like utilizing every hour of the day for study leads to better outcomes, the reality is quite the opposite. Lack of proper rest can negatively impact your brain, especially when it comes to sleep and memory retention. You’ll […]
Read MoreWelcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 23: The two strands in DNA are not identical but are complementary. Explain.....
Comments
Thanx for the help...
bullshit