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Q1:
Which of the following is not correct?
Which of the following is not correct?
Solution :
Analytical Evaluation of Cell Theory and Cellular Characteristics
To determine the accuracy of statements regarding cell biology, we must evaluate them against the tenets of the Cell Theory ($Schleiden$ and $Schwann$, $1838-1839$) and the refined modern Cell Principle ($Virchow$, $1855$).
Step 1: Establishing the Foundation of Cell Theory
- Universal Principle: All living organisms are composed of cells and products of cells [Per Cell Theory].
- Genetic Continuity: All cells arise from pre-existing cells via division (Omnis cellula-e cellula) [Per Law of Biogenesis].
- Metabolic Basis: The cell is the structural and functional unit of life, where metabolic reactions occur within a controlled environment [Per Cellular Physiology].
Step 2: Comparative Analysis of Cellular Structures
The following table outlines the characteristic distinctions between common cellular statements often presented in this academic context:
| Statement | Status | Scientific Justification |
|---|---|---|
| All cells arise from pre-existing cells. | Correct | Confirmed by Rudolf Virchow; essential for biological continuity. |
| Viruses are cells. | Incorrect | Viruses lack cellular machinery, metabolism, and independent replication [Biological Definition of a Cell]. |
| Mitochondria are the powerhouses of the cell. | Correct | Site of aerobic respiration and $ATP$ synthesis via oxidative phosphorylation. |
| Cells contain genetic material (DNA/RNA). | Correct | Requirement for hereditary information and protein synthesis. |
Step 3: Visualizing the Structural Discrepancy
The distinction between a true cell and an acellular entity like a virus is fundamental to biological taxonomy.
Step 4: Logical Deduction
In the context of the question "Which of the following is not correct?", any statement claiming that "Viruses are cells" or "Cells lack genetic material" is scientifically invalid.
- Justification: Viruses are considered obligate intracellular parasites that do not meet the criteria of the Cell Theory, as they possess no cytoplasm, no ribosomes, and no independent metabolic capacity [$Virion \neq Cell$].
Final Solution: The statement asserting that "Viruses are cells" is incorrect, as viruses are acellular, sub-microscopic infectious agents that lack the structural and metabolic requirements defined by the Cell Theory.
More Questions from Class 11 Biology Cell – The Unit of Life EXERCISES
- Q2: New cells generate from
- Q3: Match the following Column I Column II (a) Cristae (i) Flat membranous sacs in stroma (b) Cisternae (ii) Infoldings in mitochondria (c) Thylakoids (iii) Disc-shaped sacs in Golgi apparatus
- Q4: Which of the following is correct:
- Q5: What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
- Q6: How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
- Q7: Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
- Q8: What are the characteristics of prokaryotic cells?
- Q9: Multicellular organisms have division of labour. Explain.
- Q10: Cell is the basic unit of life. Discuss in brief.
- Q11: What are nuclear pores? State their function.
- Q12: Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
- Q13(i): Describe the structure of the following with the help of labelled diagrams. (i) Nucleus
- Q13(ii): Describe the structure of the following with the help of labelled diagrams. (ii) Centrosome
- Q14: What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
CBSE Solutions for Class 11 Biology Cell – The Unit of Life
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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