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Lecture 2 Cell_structure_function.pptx.....
- 1. Cell Theory, Types &Structure
- 2. Cells are thefundamental unit of life and capable of performing life functions. Cell Theory Cell theory was proposed by German scientist Theodor Schwann, Matthias Schleiden and Rudolf Virchow The cell theory states that • All living species on earth are composed of cells. • A cell is basic unit of life. • All cells arise from pre existing cells. A modern version of cell theory states that • Energy flows within the cells • Genetic information is passed on from one cell to the other • The chemical composition of all the cell is the same
- 3. Differentiation in cells:Transformation of a cell from one type to other, mostly a more specialised one, happens during the development of a multicellular organism Organelle Cell tissue organ organ system ⇨ ⇨ ⇨ ⇨ ⇨ Organisms
- 4. Examples of Cells AmoebaProteus Plant Stem Red Blood Cell Nerve Cell Bacteria
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- 6. Prokaryotic •Do not havewell defined nucleus and other membrane-bound organelles. •Few internal structures •One-celled organisms, Bacteria
- 7. Eukaryotic • Contain organellessurrounded by membranes • Most living organisms have this type of cell Plant Animal
- 8. Features Prokaryotes Eukaryotes Unicellularorganism Usually Multicellular organism Size 0.1 - 5.0µm 10-100µm Nucleus A well-defined nucleus is absent. Instead, nucleoid is present. A well-defined nucleus is present bounded by nuclear membrane Genetic material DNA is circular and double stranded. DNA is linear and double stranded Organelles Organelles are not membrane bound, if present. Mitochondria, Endoplasmic reticulum, Lysosomes and Golgi apparatus are absent Organelles are membrane bound. Ribosome 70S 80S Mode of reproduction Asexual Mostly sexual Replication Single origin of replication Multi origins of replication Based on the structure and function of cells, organisms are classified into prokaryotes and eukaryotes
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- 12. Cell Wall :Surrounding the cell and outside the cell membrane • Most commonly found in plant cells & bacteria, not in animal cell • Supports & protects cells
- 13. Cell / PlasmaMembrane: Surrounding the cell • Outer membrane of cell that controls passage of materials into and out of the cell • Double layer of phospholipid • Polar ends facing the inner, non polar ends opposed at the center of the bilayer
- 14. Inside the Cell: Different Organelles
- 15. Nucleus • Largest cellorganelle • Round or oval body lying in the centre of the cell enclosed by a double membrane • In certain regions the membranes join together and there may be pores which act as a direct passage route for the substances to leave and enter the nucleus • Contains network of thread like structures called chromatin fibres which contain DNA
- 16. Nuclear Membrane • Surroundsnucleus • Made of two layers • Openings allow material to enter and leave nucleus
- 17. Chromosomes • Present innucleus • Made of DNA • Carries genetic information from generation to generation
- 18. Nucleolus • One ormore round shaped structures present inside the nucleus • Produces ribosomes • Participates in protein synthesis by forming and storing RNA
- 19. Cytoplasm •All the partstogether inside the plasma membrane excluding nucleus •Contains a mixture of water and soluble compounds and various organelles •All metabolic activities occur in it.
- 20. Endoplasmic Reticulum •Irregular networkof double membraned tubules •It is continuous with the plasma membrane on the outside and the nuclear membrane on the inside •Smooth endoplasmic reticulum without ribosomes and rough endoplasmic reticulum with ribosomes attached •Synthesis and transport of proteins and fats
- 21. Ribosomes • Small granuleseither scattered in the cytoplasm or attached to the outside of endoplasmic reticulum • Single walled, dense, spherical bodies composed mainly of RNA • Make proteins
- 22. Mitochondria •Double walled; innerwall thrown into folds •Have their own DNA •Also contain their own ribosomes • Produces energy in form of ATP through chemical reactions – breaking down fats & carbohydrates •Seat of cellular aerobic respiration and stores energy • Synthesis of respiratory enzymes
- 23. Golgi Bodies • Movematerials within the cell • Synthesis and secretion of enzymes, hormones •Stacks of flattened membrane sacs •Consists of tubules vesicles and vacuoles
- 24. Lysosome •Digestive 'plant' for proteins,fats, and carbohydrates •Transports undigested material to cell membrane for removal •Cell breaks down if lysosome explodes
- 25. Vacuoles • Membrane-bound sacsfor storage, digestion, and waste removal • Contains water solution • Help plants maintain shape • Storage of water and other substances, food, pigments and waste products • Give turgidity to the plant cells by pressing against cell wall
- 26. Chloroplast •Usually found inplant cells •Contains green chlorophyll •Where photosynthesis takes place