Chap#3|Nucleus|Nuclear envelope|Nucleolus|FSc biology part 1|New Edition Book скачать в хорошем качестве

Chap#3|Nucleus|Nuclear envelope|Nucleolus|FSc biology part 1|New Edition Book

Here’s a clear, exam-oriented and detailed summary of Chapter 3: Nucleus, Nuclear Envelope & Nucleolus for FSc Biology Part I (New Edition Book). 🌟 Chapter 3 – The Nucleus The nucleus is the most important and largest organelle found in eukaryotic cells. It acts as the control center of the cell. 📌 1. Definition of Nucleus The nucleus is a spherical or oval organelle bounded by a membrane, containing genetic information (DNA) that regulates all cellular activities including growth, metabolism, and reproduction. 📌 2. History Discovered by Robert Brown (1831) in plant cells. Called the “nucleus” because it seemed like the core or center of the cell. 📌 3. Structure of the Nucleus The nucleus has several main parts: A) Nuclear Envelope B) Nucleoplasm C) Chromatin / Chromosomes D) Nucleolus 🧱 A. Nuclear Envelope ✅ Definition A double membrane that surrounds the nucleus and separates it from the cytoplasm. 📌 Structure Composed of two lipid bilayers: Outer nuclear membrane Inner nuclear membrane Between them is the perinuclear space. ❗ Features ✔ Nuclear pores: Tiny openings in the envelope. Allow transport of molecules (like RNA and proteins) between nucleus and cytoplasm. ✔ Outer membrane is continuous with the rough endoplasmic reticulum (RER). ✔ Inner membrane supported by protein network called nuclear lamina. 📌 Functions Protects the genetic material (DNA). Controls the movement of substances in and out of the nucleus. Maintains the shape and structure of nucleus. 🧪 B. Nucleoplasm The semi-fluid matrix inside the nucleus. Contains chromatin, nucleolus, and nuclear solutes. 🧬 C. Chromatin and Chromosomes Chromatin: Long, thread-like DNA + protein complex. During cell division, chromatin condenses into chromosomes. Chromosomes: Carry hereditary information. Each species has a specific number (e.g., humans have 46). 🌑 D. Nucleolus (Plural: Nucleoli) ✅ Definition A dense, spherical structure inside the nucleus where ribosomal RNA (rRNA) is made. 📌 Features Not surrounded by a membrane. May be one or more per nucleus. Visible clearly during interphase. 📌 Functions ✔ Ribosomal RNA (rRNA) synthesis ✔ Assembly of ribosomal subunits ✔ Plays a role in protein synthesis indirectly. 📌 Summary Table Component Structure Function Nuclear Envelope Double membrane with pores Protects DNA & controls transport Nucleoplasm Jelly-like fluid inside nucleus Medium for nuclear activities Chromatin / Chromosomes DNA + proteins Genetic material, inheritance Nucleolus Dark region without membrane rRNA synthesis & ribosome assembly 📌 Key Points for FSc Exams ✔ Nucleus is the control center of the cell. ✔ Nuclear envelope has two membranes and nuclear pores. ✔ Nucleolus makes rRNA and assembles ribosomes. ✔ Chromatin changes to chromosomes during cell division.