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Q3:
From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
Solution :
1. Theoretical Comparison: Molecular Size of DNA vs. Proteins (Enzymes)
To determine the relative molecular size, we must evaluate the structural composition and the typical molecular weight ranges of biological macromolecules. DNA (Deoxyribonucleic acid) exists as a long, polymer chain of nucleotides, while enzymes are functional proteins (polymers of amino acids).
2. Analysis of Molecular Weight and Dimensions
The molecular size of a macromolecule is proportional to its polymerization length. We analyze this based on the following criteria:
| Feature | Enzymes (Proteins) | DNA (Genomic) |
|---|---|---|
| Basic Unit | Amino Acids | Nucleotides |
| Molecular Weight | $10^4$ to $10^6$ Daltons | $10^9$ to $10^{12}$ Daltons (for genomic DNA) |
| Structural Nature | Globular/Tertiary folding | Extremely long linear/helical chain |
3. Step-by-Step Derivation and Justification
Step 1: Genomic Scale Analysis
In a typical prokaryotic cell like E. coli, the genomic DNA contains approximately $4.6 \times 10^6$ base pairs. Each base pair has an average molecular weight of $650$ Daltons. Therefore, the total molecular weight is approximately $3 \times 10^9$ Daltons [Based on the stoichiometry of the double helix].
Step 2: Protein/Enzyme Scale Analysis
Most enzymes consist of one or more polypeptide chains. Even large multi-subunit enzymes, such as DNA Polymerase or Rubisco, typically have molecular weights in the range of $10^5$ to $5 \times 10^5$ Daltons. Even when considering complex quaternary structures, they remain significantly smaller than the chromosome from which they were encoded.
Step 3: Comparison of Physical Dimensions
The physical length of DNA is astronomical compared to protein molecules. For instance, the human genome stretched out is approximately $2$ meters long per cell, whereas enzymes are nanometer-scale globular structures [Determined by X-ray crystallography and electron microscopy data].
4. Visual Representation of Relative Scale
5. Conclusion of Evidence
DNA is significantly bigger in molecular size than enzymes. We know this through:
- Stoichiometric Analysis: The calculation of total atomic weight per chromosome exceeds the weight of any single functional protein complex by multiple orders of magnitude.
- Gel Electrophoresis Observations: During techniques like Agarose Gel Electrophoresis, genomic DNA remains at the top (well) due to its inability to migrate through the matrix as quickly as smaller proteins, confirming its larger molecular size [Ref: Principle of Electrophoretic Mobility].
Final Solution: DNA is significantly larger than enzymes in molecular size because it functions as the massive, linear storage repository for genetic information, whereas enzymes are compact, folded proteins optimized for specific catalytic activities within a cell.
More Questions from Class 12 Biology Biotechnology: Principles and Processes EXERCISES
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q11(a): Explain briefly (a) PCR
- Q11(a): Explain briefly (a) PCR
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(c): Explain briefly (c) Chitinase
- Q11(c): Explain briefly (c) Chitinase
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
CBSE Solutions for Class 12 Biology Biotechnology: Principles and Processes
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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