Class 11 Biology - HARYANA
Cell: The Unit of Life
The chapter 'Cell: The Unit of Life' forms the foundation of cellular biology in the Class 11 Haryana (BSEH) curriculum. It explores the cell theory, the structural differences between prokaryotic and eukaryotic cells, and the detailed anatomy of plant and animal cells. Students learn about the various cell organelles such as the plasma membrane, endomembrane system, mitochondria, ribosomes, and nucleus, along with their specific functions. This chapter is vital for board exams as it carries significant weightage, frequently featuring diagram-based questions, short-answer differences between prokaryotes and eukaryotes, and detailed structural functions of key organelles.
Start Learning FreeKey Concepts
Cell Theory
Formulated by Schleiden, Schwann, and later modified by Rudolf Virchow, it states that all living organisms are composed of cells and products of cells, and all cells arise from pre-existing cells.
Prokaryotic vs Eukaryotic Cells
Prokaryotic cells lack a membrane-bound nucleus and true organelles (e.g., bacteria), whereas eukaryotic cells possess a distinct, membrane-bound nucleus and organized membrane-bound organelles (e.g., plant and animal cells).
Plasma Membrane Structure
Described by the fluid mosaic model proposed by Singer and Nicolson, the cell membrane consists of a lipid bilayer with embedded mosaic proteins that provide fluidity and selective permeability.
Endomembrane System
A coordinated network of membrane-bound organelles including the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and vacuoles whose functions are coordinated.
Mitochondria and Plastids
Mitochondria are the powerhouse of the cell responsible for aerobic respiration and ATP production, while plastids (like chloroplasts) are found in plant cells and capture light energy for photosynthesis.
Important Formulas
Board Exam Info
In the Haryana Board (BSEH) Class 11 Biology exams, this chapter typically carries around 5 to 7 marks. Common question types include short-answer questions (differentiating between plant and animal cells, or prokaryotes and eukaryotes), very short questions on organelle functions, and 3 to 5-mark diagram-based questions requiring the structural labeling of a typical eukaryotic cell, mitochondria, or chloroplast.
Frequently Asked Questions
Why is the cell called the structural and functional unit of life?
Because all living organisms are built from cells (structural), and all metabolic and life-sustaining biochemical reactions take place within these cells (functional).
What is the main difference between 70S and 80S ribosomes?
70S ribosomes are smaller and found in prokaryotic cells as well as inside mitochondria and chloroplasts, whereas 80S ribosomes are larger and found in the cytoplasm of eukaryotic cells.
Are plasmids present in all cells?
No, plasmids are extra-chromosomal, circular DNA molecules typically found only in prokaryotic cells (like bacteria) and do not occur in normal eukaryotic cells.
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