🧬 Eukaryotic Nucleus – Structure, Functions & NEET Highlights

🔍 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)