🧬 Eukaryotic Nucleus – Structure, Functions & NEET Highlights

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🔍 1. What is the Nucleus?

The nucleus is the largest membrane-bound organelle in a eukaryotic cell, often referred to as the “control center” of the cell.


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🧫 2. Structure of Eukaryotic Nucleus

Component Description

Nuclear envelope Double membrane with pores; separates nucleus from cytoplasm
Nuclear pores Allow transport of RNA, proteins
Nucleoplasm Gel-like substance (nuclear sap) inside nucleus
Chromatin DNA + histone proteins; forms chromosomes
Nucleolus Non-membranous structure for rRNA synthesis and ribosome assembly


🧠 Mnemonic:
“NEVER PLAY CARDS NEAR NUCLEUS”
(Nuclear envelope, Pores, Chromatin, Nucleoplasm, Nucleolus)


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🔄 3. Functions of Nucleus

🧠 Controls cell activities (via gene expression)

💾 Stores genetic material (DNA)

🔁 DNA replication before cell division

🧬 Transcription of RNA from DNA

🧪 Ribosome production in the nucleolus



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🧵 4. Chromatin Types

Type Feature

Euchromatin Light, active DNA, loosely packed
Heterochromatin Dark, inactive DNA, tightly packed


➡ During cell division, chromatin condenses to form chromosomes.


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❗ Key NEET Points

✅ Nuclear envelope = double membrane
✅ Nucleolus is non-membranous
✅ Nucleus absent in mature RBCs
✅ All genetic info (DNA) stored in chromatin


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📊 Summary Table

Feature Nucleus

Membrane Double
Shape Spherical / Oval
Function Genetic control
Special Part Nucleolus (makes rRNA)

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