Class 11 Biology - WEST-BENGAL
Cell: The Unit of Life
The chapter 'Cell: The Unit of Life' forms the foundational core of cell biology in the Class 11 West Bengal Council of Higher Secondary Education (WBCHSE) curriculum. It introduces students to the structural and functional unit of all living organisms. You will explore the Cell Theory, the detailed differences between Prokaryotic and Eukaryotic cells, and the ultra-structure of plant and animal cells. Key cellular organelles such as the plasma membrane, mitochondria, ribosomes, and nucleus are discussed in depth. Mastering this chapter is crucial for board exams as it builds the bedrock for subsequent chapters in plant physiology, genetics, and human biology.
Start Learning FreeKey Concepts
Cell Theory
Formulated by Schleiden, Schwann, and later expanded by Rudolf Virchow, it states that all living things are made of cells and all cells arise from pre-existing cells.
Prokaryotic vs Eukaryotic Cells
Prokaryotic cells lack a true membrane-bound nucleus and distinct organelles (e.g., bacteria), whereas eukaryotic cells possess a well-defined nucleus and membrane-bound 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 interspersed proteins that allow lateral movement.
Endomembrane System
A coordinated group of membranous organelles including the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles that work together to modify, package, and transport lipids and proteins.
Mitochondria and Plastids
Known respectively as the 'powerhouse of the cell' and the site of photosynthesis, both are semi-autonomous organelles containing their own circular DNA and 70S ribosomes.
Important Formulas
Board Exam Info
In the WBCHSE Class 11 Biology annual examination, this chapter typically carries around 5 to 7 marks. Questions frequently include 1-mark objective/MCQs, 2-mark short answer questions (such as differences between prokaryotes and eukaryotes or the functions of lysosomes), and 3 to 5-mark structured questions requiring labeled diagrams of an ultrastructure of a plant or animal cell, or the fluid mosaic model.
Frequently Asked Questions
What is the main difference between 70S and 80S ribosomes?
70S ribosomes are found in prokaryotes, mitochondria, and chloroplasts and consist of 50S and 30S subunits. 80S ribosomes are found in the cytoplasm of eukaryotic cells and consist of 60S and 40S subunits.
Why are mitochondria called the powerhouse of the cell?
Mitochondria are the sites of aerobic respiration where ATP (Adenosine Triphosphate) is synthesized, which serves as the energy currency for various cellular activities.
Are viruses considered cells according to the Cell Theory?
No, viruses are considered acellular because they lack cellular machinery, cytoplasm, and metabolic activity of their own outside a host cell.
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