Class 11 Biology - CBSE
Cell: The Unit of Life
Cell: The Unit of Life is a foundational chapter in Class 11 CBSE Biology that explores the structural and functional unit of all living organisms. Students will learn about the Cell Theory, the differences between prokaryotic and eukaryotic cells, and the detailed architecture of plant and animal cells. Key topics include the plasma membrane, cell wall, endomembrane system, mitochondria, plastids, and the nucleus. Mastering this chapter is crucial for board exams as it forms the basis for subsequent chapters in plant physiology, human physiology, and genetics, frequently appearing in both direct theoretical questions and diagram-based evaluations.
Start Learning FreeKey Concepts
Cell Theory
Formulated by Schleiden, Schwann, and later expanded by Rudolf Virchow, it states that all living things are composed of cells and products of cells, and all cells arise from pre-existing cells (Omnis cellula e cellula).
Prokaryotic vs Eukaryotic Cells
Prokaryotic cells lack a membrane-bound nucleus and distinct organelles (e.g., bacteria), whereas eukaryotic cells possess a true membrane-bound nucleus and complex cytoplasmic organelles (e.g., plant and animal cells).
Fluid Mosaic Model
Proposed by Singer and Nicolson, this model describes the plasma membrane as a fluid phospholipid bilayer with proteins embedded in it, allowing lateral movement of molecules.
Endomembrane System
A coordinated network of membranous organelles including the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles whose functions are coordinated.
Mitochondria and Plastids
Semi-autonomous organelles containing their own DNA and ribosomes; mitochondria are the powerhouse of the cell, while plastids (like chloroplasts) are involved in photosynthesis.
Important Formulas
Board Exam Info
In the CBSE Class 11 Biology examination, this chapter typically carries around 5 to 7 marks. Questions frequently include diagram-based labeling (such as the ultrastructure of a plant cell or mitochondrion), direct structural and functional differences between prokaryotes and eukaryotes, and functions of specific cell organelles.
Frequently Asked Questions
Mitochondria are called the powerhouse of the cell because they produce cellular energy in the form of ATP (Adenosine Triphosphate) through aerobic respiration.
Mitochondria are called the powerhouse of the cell because they synthesize ATP through cellular respiration, which provides energy for various metabolic activities.
What is the main difference between plant and animal cells?
Plant cells have a rigid outer cell wall, large central vacuoles, and plastids (like chloroplasts), whereas animal cells lack cell walls and plastids, and possess small, temporary vacuoles and centrioles.
Are viruses considered living cells under the Cell Theory?
No, viruses are considered acellular and are an exception to the Cell Theory because they lack cellular machinery and can only replicate inside a host cell.
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