STRUCTURE AND FUNCTIONS OF NUCLEUS & NUCLEOLUS
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The document provides an overview of the nucleus, highlighting its role as the control center for cellular activities and detailing its structure, chemical composition, and variations among different cell types. It describes the sizes of nuclei across various organisms and the components of the nuclear membrane, nucleoplasm, and chromatin, as well as the functions of the nucleolus. Additionally, it explains the types of chromatin and their significance during cell division.
STRUCTURE AND FUNCTIONS OF NUCLEUS & NUCLEOLUS
- 1. NUCLEUS
- 2. NUCLEUS • Controls –cellular activities • Controlling centre • Robert brown-1831 • Karyology • +all Eukaryotes • - RBC,Lence cells of eye
- 3. NUCLEUS • Cell-1 nucleus-2 or more • Types of cells based on no of nucleus 1. Mononucleate- Amoeba, typical cell 2. Binucleate-Paramecium,cartilage,liver 3. Polynucleate-Opalina
- 4. NUCLEUS • Shape: –Shape of the cell –Generally Spherical • Chemical nature: –80%-Proteins –12% DNA –5%RNA –3%Lipids
- 5. NUCLEUS Size • Not constant-cell type • 10% cell volume • 3μm -25 μm • Size directly proportional to cytoplasm • More volume-larger nucleus
- 6. NUCLEUS R.HERTWIG Volume of nucleus (NP) Volume of cytoplasm-volume of nucleus Vn Vc-Vn Vn =Volume of nucleus Vc =Volume of Cytoplasm Nucleo cytoplasmic index = (NP)=
- 7. NUCLEUS • Structure 1. Nuclear membrane 2. Nucleoplasm 3. Chromatin reticulam 4. nucleolus
- 8. NUCLEAR MEMBRANE Semipermiable membrane Double layer-Outer, inner layer Perinuclear space(10-15 nm) Minute pores-circular-exchange Outer rough,inner smooth Outer inner layer
- 9. NUCLEAR SAP • Nucleoplasm/karyolymph • Transparent,semi-solid,acidophilic • Chromatin,nucleolus-suspended • Organic,inorganic-Nucleic acids,Proteins,Enzymes,minerals
- 10. CHROMATIN RETICULAM • Thread like structures- Chromonemata • Net work-Chromatin reticulam • Cell division-chromatin-ribbon like chromosomes • Chemically-DNA,Proteins • 2 types 1. Euchromatin 2. Heterochromatin
- 11. CHROMATIN RETICULAM 1. Hetero chromatin • Darkly stain,condensed • Small-DNA,Large RNA 2.EuChromatin Light stained,diffused Large DNA,Small RNA
- 12. 4.NUCLEOLUS • Discovered- Fontana • Coined –Bowman • Distinct in interphase • Disappear-Pro,meta,ana phase • Reappear telophase • Non membrane • Number depends on chromosome sets • Composed –RNA ,Proteins • Function-rRNA,Prorein
- 13. FUNCTIONS • Control cellular activities • Master plan for protein • Nucleolus-Ribosomes • rRNA synthesis • Reg-cell cycle • Heredity