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Q9:
List two essential roles of ribosome during translation.
Solution :
Step 1: Structural Basis of Ribosomal Functionality
The ribosome acts as a complex molecular machine consisting of catalytic $rRNA$ molecules and structural proteins. During the process of translation, the ribosome exists as two subunits: the $30S$ (small) subunit and the $50S$ (large) subunit in prokaryotes, which assemble on the $mRNA$ template. Its primary roles are defined by its ability to facilitate the precise decoding of genetic information [Per the Central Dogma of Molecular Biology].
Step 2: Role 1 – Decoding and Alignment of Aminoacyl-tRNA
The ribosome serves as a physical scaffold that positions the $mRNA$ transcript and the aminoacyl-$tRNA$ molecules in a specific spatial orientation.
- Codon-Anticodon Pairing: The small subunit holds the $mRNA$ codon in place, ensuring that the complementary anticodon of the $tRNA$ binds accurately [By the principle of complementary base pairing].
- The A, P, and E Sites: The ribosome creates three distinct binding sites—the $A$ (aminoacyl) site, the $P$ (peptidyl) site, and the $E$ (exit) site—which govern the order of amino acid addition.
Step 3: Role 2 – Peptidyl Transferase Activity (Catalysis)
The ribosome acts as a ribozyme, specifically utilizing the $23S$ $rRNA$ (in prokaryotes) or $28S$ $rRNA$ (in eukaryotes) to catalyze the formation of peptide bonds between amino acids.
The reaction can be expressed as:
$Peptidyl\text{-}tRNA + Aminoacyl\text{-}tRNA \xrightarrow{Ribozyme} Peptidyl\text{-}tRNA_{n+1} + tRNA_{empty}$
This activity ensures that the polypeptide chain grows in a linear, sequential manner dictated by the sequence of codons [Per the mechanism of ribosomal catalysis].
Visual Representation of Ribosomal Translation
Summary of Functional Roles
| Role | Biological Significance |
|---|---|
| Decoding | Ensures fidelity by matching $tRNA$ anticodons to $mRNA$ codons. |
| Catalysis | Facilitates the peptide bond formation via $23S/28S$ $rRNA$ activity. |
Final Solution: The two essential roles of the ribosome are: (1) acting as a molecular scaffold to facilitate the accurate pairing of $mRNA$ codons with $tRNA$ anticodons, and (2) functioning as a ribozyme (peptidyl transferase) to catalyze the formation of peptide bonds between successive amino acids in a polypeptide chain.
More Questions from Class 12 Biology Molecular Basis of Inheritance EXERCISES
- Q1: Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
- Q1: Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
- Q2: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
- Q2: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
- Q3: If the sequence of one strand of DNA is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of complementary strand in 5'\(\rightarrow\)3' direction.
- Q3: If the sequence of one strand of DNA is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of complementary strand in 5'→3' direction.
- Q4: If the sequence of the coding strand in a transcription unit is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of mRNA.
- Q4: If the sequence of the coding strand in a transcription unit is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of mRNA.
- Q5: Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q5: Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q6: Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
- Q6: Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
- Q7: How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
- Q7: How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
- Q8(a): Differentiate between the followings: Repetitive DNA and Satellite DNA
- Q8(a): Differentiate between the followings: (a) Repetitive DNA and Satellite DNA
- Q8(b): Differentiate between the followings: mRNA and tRNA
- Q8(b): Differentiate between the followings: (b) mRNA and tRNA
- Q8(c): Differentiate between the followings: Template strand and Coding strand
- Q8(c): Differentiate between the followings: (c) Template strand and Coding strand
- Q9: List two essential roles of ribosome during translation.
- Q10: In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
- Q10: In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
- Q11(a): Explain (in one or two lines) the function of the followings: (a) Promoter
- Q11(a): Explain (in one or two lines) the function of the followings: Promoter
- Q11(b): Explain (in one or two lines) the function of the followings: (b) tRNA
- Q11(b): Explain (in one or two lines) the function of the followings: tRNA
- Q11(c): Explain (in one or two lines) the function of the followings: (c) Exons
- Q11(c): Explain (in one or two lines) the function of the followings: Exons
- Q12: Why is the Human Genome project called a mega project?
- Q12: Why is the Human Genome project called a mega project?
- Q13: What is DNA fingerprinting? Mention its application.
- Q13: What is DNA fingerprinting? Mention its application.
- Q14(a): Briefly describe the following: (a) Transcription
- Q14(a): Briefly describe the following: Transcription
- Q14(b): Briefly describe the following: (b) Polymorphism
- Q14(b): Briefly describe the following: Polymorphism
- Q14(c): Briefly describe the following: (c) Translation
- Q14(c): Briefly describe the following: Translation
- Q14(d): Briefly describe the following: (d) Bioinformatics
- Q14(d): Briefly describe the following: Bioinformatics
CBSE Solutions for Class 12 Biology Molecular Basis of Inheritance
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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