CELL : THE FUNDAMENTAL UNIT OF LIFEBY: Ms. VASUDHA SINGHROBERT HOOKE WAS THE FIRST SCIENTIST TO PEER THROUGH A MICROSCOPE AND OBSERVE CELLS WHICH ARE NOW CONSIDERED THEBUILDING BLOCKS OF LIFE.ONION PEEL CHEEK CELLSIN-TEXT QUESTIONS1.Who discovered cells and how?A.Cells were discovered by an English botanist,Robert Hooke ,in 1665.He used primitive microscope to observe cells in a cork slice.2.Why is the cell called the structural and functional unit of life?A. A cell is the smallest unit of life and is capable of all living functions.They are the building blocks of life.The shape and size of the cell is related to the function they perform.That is why they are called thestructural and functional unit of life.Defne Hypotonic solution?Hypotonic solution is the solution surrounding the cell that has higherwaterconcentration than the cell.Water molecules are free to pass across the cell membrane in both the directions but more water will come into the cell than will leave. The net result is that water enters the cell and cell swells up.In plant cells ,cells become turgid while in animals, cells burst .Hypertonic solutionWhen a medium surrounding the cell has lower concentration of water than that in the cell.Water molecules are free to pass across the cell membrane in both the directions, but more water leaves the cell than enters itThe cell will shrink i.e. it will undergo plasmolysisIsotonic solutionIf the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell.Water crosses the cell membrane in both the directions but amount of water going in is the same as going out.The cell will stay the same size.PHAGOCYTOSIS IN AMOEBAHow do substances like CO2 and water move in and out of the cell? DiscussA. Movement of CO2 and O2Gases like CO2 and O2 move across the cell membrane by a process called difusion. If the concentration of CO2 is high inside the cell than outside ,then CO2 will move from region of higher concentration to lower.Similarly,O2 enters the cell by the process of difusion when its concentration inside the cell decreases.Movement of waterThe movement of water molecules through a cell membrane is called difusion. Movement of water is afected by the amount of solute dissolved in it. Movement of water is from a region of high water concentration through a semi permeable membrane to a region of lowwater concentration.Why is the plasma membrane called a selectively permeable membrane?A. The plasma membrane is called a selectively permeable membrane because it allows entry and exit of some molecules through the cell and prevents the movement of other molecules.CELL WALLHard outer covering of the cellPresent outside the cell wallCell wall is composed of celluloseCelluloseis a complex substance and provides structural strength to plantsCell wall is present in plant cells .Cell wall helps the plant cell to withstandenvironmental changes.NUCLEUSHas double layered covering called nuclear membraneNuclear membrane has pores which allow the transfer of materials from inside to outside i.e. cytoplasmNucleus contains chromosomes which are visible as rod shaped structures when the cell is about to divideChromosomes contain genetic information for inheritance of features from parents to offspring in the form of DNA.Functional segments of DNA are called genes.FUNCTIONSt plays an important role in Cellular reproduction.t determines cellular development by directing chemical activities of cell.CYTOPLASMIt is the fuid content inside the plasma membraneIt contains many specialized cell organelles.Functions of RERServe as channels for transport of proteins synthesized by ribosomes.Provides cytoplasmic framework for the cellFunctions of SERHelps in manufacture of fat molecules or lipidsInvolved in membrane biogenesis(formation of cell membrane by proteins and lipids)Detoxifes drugs and toxins in liverRIBOSOMESSite of protein synthesisLYSOSOMES!aste disposal system of the cellContain powerful digestive en"ymes capable of digesting organic material.!hen cell gets damaged# lysosomes may burst and the en"ymes digest their own cell. $herefore# they are also %nown as &suicide bags' of the cell.(n"ymes are made by )() and pac%aged by *olgi +odiesMITOCHONDRIA,nown as power house of the cell(nergy is released by mitochondria in the form of A$PA$P is %nown as the energy currency of the cell.t is an autonomous organelle. +ecause of its DNA and ribosomes it can synthesi"e some of its own proteins.nner membrane forms finger li%e folds %nown as cristae.Cristae increase surface area for A$P synthesis.PLASTIDSThey are of two types-Chromoplast and LeucoplastChromoplast are coloured plastids, e.g,1. Name the scientist who discovered ce.".Name the scientist who #rst descri$ed %o&i a''arat(s.). *A+What is ,NA- Where is it .o(nd-*/+ Name the .(nctiona se&ment o. ,NA.0. List two simiarities $etween mitochondria and 'astids.1. Name the or&anee that is re.erred to as the 2'owerho(se o. the ce3. Wh4 is it caed so-5. Mention an4 two .(nctions o. the endo'asmic retic((m.6. %ive the .(nctions o. the .oowin& or&anees in a ce.*i+ Choro'ast*ii+ N(ce(s7. Which ce or&anee is caed 2s(icide $a& o. a ce3- Wh4-8. Write the names o. two ce or&anees that have their own ,NA and ri$osome.19. State an4 two reasons .or 'ant ces to have ar&e centra vac(oe.IDENTIFY THE CELL ORGANELLES-