The cell is the fundamental, structural and functional unit of all living organisms.
1. Chapter 3: CELL STRUCTURE & FUNCTION Unit 1: CELL: THE UNIT OF LIFE Cell Structure and Organelles Cell Molecular Components What is a cell? Water and Chemical properties Cell Membrane Cell theory Osmotic Properties of cells An overview of a cell Cell molecule transportation VIKASANA - BRIDGE - COURSE 2012
2. WHAT IS A CELL? Cell is the fundamental, structural and functional unit of all living organisms Robert Hooke (1665) – an English scientist who observed honeycomb like dead cells and coined the term CELL Anton Von Leeuwenhock first described a living cell (1667) Robert Browne discovered nucleus (1833) VIKASANA - BRIDGE - COURSE 2012
3. Mathias J Schleiden (1838) ; a German botanist and Theodore Schwann (1839) ; a British Zoologist proposed cell theory. All living organisms are composed of cells and product of cells All cells arise from pre existing cells through the process of cell division The body of living organisms is made up of one or more cells VIKASANA - BRIDGE - COURSE 2012
4. Unicellular organisms – Organisms with single cell, capable of independent existence and carries all functions like digestion,excretion ,respiration ,growth & reproduction (Acellular). Examples , Amoeba, Euglena Multicellular organisms – Organisms with more than one cell Cells in multicellular organisms vary in size & shape depending on function. VIKASANA - BRIDGE - COURSE 2012
5. SHAPE: Parenchyma - Polyhedral cells performs storage. Sclerenchyma - spindle shaped cells & provides mechanical support, Nerve cells- long and branched cells conducting nerve impulses RBC -Biconcave & helps in carrying oxygen Muscle cells- cylindrical or spindle shaped concerned with the movement of body parts. VIKASANA - BRIDGE - COURSE 2012
7. SIZE: varies from few microns (1cm= 10mm; 1mm=1000µm) to few cms Smallest living cell is PPLO ( Pleuro Pneumonia Like Organism) - 0.1µm Largest living cell is Egg of an Ostrich , 170 to 180 mm in diameter. Bacteria – 0.1 to 0.5 µm Sclerenchyma fibre upto 60cms in length IKASANA - BRIDG - COURSE 2012
8. Cell has non living outer layer called CELL WALL found only in plant cells Below cell wall is CELL MEMBRANE CELL MEMBRANE encloses PROTOPLASM PROTOPLASM has semi fluid matrix called CYTOPLASM and large membrane bound structure called NUCLEUS VIKASANA - BRIDGE - COURSE 2012
9. CYTOPLASM has many membrane bound organelles like Endoplasmic reticulum , Golgi Bodies Mitochondria ,Plastids and vacuoles. They also have non membrane bound structures called Ribosomes and Centrosomes Cytoplasm without Cell organelles are called Cytosol. VIKASANA - BRIDGE - COURSE 2012
13. Outermost layer, non living ,rigid Found in bacterial cells, fungal cells and plant cells. Permeable Made up of cellulose (in bacteria- peptidoglycans, in fungus- Chitin) FUNCTION : Rigidity, mechanical support and protection VIKASANA - BRIDGE - COURSE 2012
14. Present in all cells, just below the cell wall in plant cells, outermost membrane in animal cells Semi-permeable Made up of phospholipids, proteins, carbohydrates and Cholesterol FUNCTION : It allows outward and inward movement of molecules across it like diffusion, osmosis, active transport, phagocytosis and pinocytosis VIKASANA - BRIDGE - COURSE 2012
15. CELL MEMBRANE VIKASANA - BRIDGE - COURSE 2012
16. According to Huxley , protoplasm is “physical basis of life” Includes organic and inorganic molecules CYTOPLASM Semi fluid matrix present between cell membrane and nuclear membrane It has various living cell inclusions called cell organelles and non living substances called Ergastic substances VIKASANA - BRIDGE - COURSE 2012
17. STRUCTURE: Largest cell organelle present in eukaryotic cells It is usually spherical It has double layer nuclear membrane with nuclear pores It has transparent granular matrix called nucleoplasm, chromatin network composed of DNA and histone proteins It also has a spherical body called Nucleolus FUNCTION: It is the control centre of the cell. It contains genetic material DNA which regulates all metabolic activities of the body VIKASANA - BRIDGE - COURSE 2012
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20. Nucleus of a non dividing cell has network of fibres called chromatin. During cell division, chromatin condenses to form distinct chromosomes. Chromosomes help in transmission of characters or genes Chromosome has centromere at the centre & arms on either sides called chromatids Chromatid- Thread like chromonema VIKASANA - BRIDGE - COURSE 2012
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22. Endoplasmic Reticulum: ER is a network of membrane bound tubular structures in cytoplasm It extends from cell membrane to nuclear membrane it exists as flattened sacks called Cisternae, unbranched tubules and oval vesicles There are two types of ER, ROUGH ER and SMOOTH ER. VIKASANA - BRIDGE - COURSE 2012
23. Helps in intracellular transportation It provides mechanical support to cytoplasmic matrix It helps in the formation of micro bodies, nuclear membrane and golgi complex. It helps in detoxification of metabolic wastes VIKASANA - BRIDGE - COURSE 2012
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25. It has a group of curved, flattened plate like compartments like Cisternae. The cisternae produce a network of tubules from the periphery These tubules end in spherical enzyme filled vesicles. Commonly called packaging centres of the cell VIKASANA - BRIDGE - COURSE 2012
26. They store the product of ER They produce Lysosomes They secrete various Enzymes, hormones and cell wall material VIKASANA - BRIDGE - COURSE 2012
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28. Spherical or rod shaped It has two membranes, outer membrane is smooth, inner membrane produces finger like infoldings called Cristae Inner membrane also has stalked particles called Racker’s particles or Oxysomes The mitochondria is filled with granular mitochondrial matrix VIKASANA - BRIDGE - COURSE 2012
29. Matrix has circular mitochondrial DNA, RNA, 70s Ribosomes, proteins, Enzymes and lipids FUNCTION: Synthesizes and stores energy rich molecules ATP(Adenosine Tri phosphate) during aerobic respiration VIKASANA - BRIDGE - COURSE 2012
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31. Present in plant cells, photosynthetic bacteria and Euglena (bacteria can be chemosynthetic also) 3 types- Chromoplast (different colored plastids), Leucoplast ( Colourless) and Chloroplast( Green colored plastids) CHLOROPLAST: (kitchen of the cell) Contains green colour pigment called chlorophylls Chloroplast has double membrane Matrix is called Stroma VIKASANA - BRIDGE - COURSE 2012
32. Stroma has membranous sacks called Thylakoids Thylakoids are arranged one above the other to form granum Grana are interconnected by Frets FUNCTION: Helps in photosynthesis VIKASANA - BRIDGE - COURSE 2012
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34. Single membrane bound sack like vesicles Absent in animal cells Plant cells have large vacuoles- distinct character Also present in lower organisms The membrane of vacuole is called tonoplast Vacuole is filled with watery fluid called cell sap which has dissolved salts, sugars, enzymes etc VIKASANA - BRIDGE - COURSE 2012
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36. Single membrane bound vesicles filled with hydrolytic enzymes found only in animal cells. Produced from golgi complex 4 types- Primary, secondary, residual & auto lysosomes FUNCTION: Intracellular digestion Destroy old and non functional cells Recycles worn out cells VIKASANA - BRIDGE - COURSE 2012
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38. RIBOSOMES (Protein factories of the cell ) Present in cytoplasm, mitochondria, chloroplast & also found attached to rough ER & nuclear membrane They are made up of r RNA and proteins Prokaryotes have 70s ribosomes, Eukaryotes have 80s ribosomes . FUNCTION: These are sites of protein synthesis VIKASANA - BRIDGE - COURSE 2012
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40. CENTROSOMES: Found in animal cells & in motile algae. It has two cylindrical structures called centrioles surrounded by centrosphere. Centrioles are arranged at right angles They are made up of micro tubules FUNCTION: Helps in cell division. NON LIVING CELL INCLUSIONS: Ergastic substances Cytoskeleton VIKASANA - BRIDGE - COURSE 2012
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