2 CELL: THE UNIT OF LIFE Cell: It is the fundamental structural and functional unit of life, Discoveries: + Simple Microscope: © Cell; Robert Hook II Theory: Matthias Schleiden, Theodor Schwann, Rudolf Virchow Cell Theory: © Cell is the structur * Allcells originate from the pre-existing cells, Structure of Cell: 1. Cell Membrane (©. Itisa thin, flexible living membrane. © Itis made up of lipoprot © Ithas fine pores and is selectively semi-permeable. ©. It is outermost in animal cells and lies next to cell wall in plant cell : Antony van Leeuwenhoek ral and functional unit of living organisms, Functions: © Regulates entry of certain solutes and ions (selectively semi-permeable), © Maintains shape of the cells in animals. sid layer surrounding the cell membrane. © It is made up of cellulose and is freely permeable. Functions: ©. It gives rigidity and shape to the plant cell © Provides protection. ‘© Allows all substances to enter and leave (freely permeable). 3. Cytoplasm © Itisa semi-liquid colourless substance © It contains a mixture of water and soluble inorganic and organic compounds and various organelles. © Ithas all the parts inside the cell membrane other than the nucleus. Functions: © Seat of initial steps of respiration. © Many chemical reactions take place with the help of enzymes. © Different organelles contained in perform different functions. 4. Cell organelles © Parts of a cell that have a definite shape, a de co. They are living parts of the cell. © Organism: Organs::Cell : Organelles . Nucleus: * Nuclear membrane,Nucleoplasm,Nueleolus,Chromatin fibres. Characteristics: © Itis the largest cell organelle. © Nuclear membrane has pores which allows certain substances to enter and leave. © Has dense nucleoplasm having one or two nucleoli and chromatin fibres. Functions: 7 oe co-ordinates various life process of the cell. ‘ins chromosomes which carry genes. ite structure and a defiNucleolus Functions: n protein synthesis by forming and sto ng RNA. and dictates them for protein synthesis, © Helps (© Produces ribosomes Chromatin Fibres © During cell division, chromatin fibres condenses to form thick and ribbon-like chromosomes. © During r ge of nucleus chromatin fibres are a network of thread like structure Functions: ‘© Chromosomes ¢: esting : y hereditary units called genes. © Genes carry hereditary characters from parents to offspring. ii, Centrosome (only in animal cell) Characteristics: © Contains 1 or 2 centrioles surrounded by microtubules called asters. Location: Near the nucleus of the animal cell Functions: ti © Initiates and regulates cell division in animal cells, © Forms spindle fibres with the help of asters. iii, Endoplasmic Reticulum Characteristies: © Irregular network of tubular double membrane structure, © Itis of two types © Smooth Endoplasmic Reticulum — without ribosomes. © Rough Endoplasmic Reticulum — with ribosomes attached. Location: Attached to the cell membrane at its outer end and nuclear membrane to its inner end. Functions: © Provides a supportive framework to the cells. © Synthesis and transport of proteins and fats, 3olgi Apparatus (Animals) / Dictyosomes (Plants) Characteristi ‘©. Stacks of flattened membranous sacs. co Consists of tubules(cisternae), vesicles and vacuoles. Location:Near the nucleus in the cytoplasm of the cell. Functions: © Synthesis and secretion of enzymes, hormones, ete, ‘© Formation of acrosome of sperm (animal cells), vy. Ribosomes ‘© Small granules without a membrane © Made up mainly of RNA. Location: Foun vnthesis. jon: Protein Syn! ome house of the cell) Endoplasmic Reticulum vi.Mitochondria (Power “haracteristi i Characte ped but usually sausage shaped, © Various s alls produced into folds called cristae. © Double walled with their inner wi © Have their own DNA and ribosomes Location: In the cytoplasm of the ceFunctions: Seat of cellular aerobic respiration. 5. Stores energy in the form of ATP. [GR] oo Synthesis of respiratory enzymes. vii, Lysosomes Characteri 5 These are membranous sacs budded off from Golgi bodies. © Contains 40 different types of digestive enzymes. Location: Found in the cytoplasm of the cell Functions: (Extracellular and Intracellular digestion) © Destroys cell organelles when the eel is old or injured. Hence, are called suic called intracellular digestion. ‘© Destroys foreign substances around them. © Formation of bones by digesting cartilage. © Digests stored food during starvation of the cell. dal bags. This process is PLASTIDS (only in plants) a, CHLOROPLAST: © Green coloured plastids. © They have double membrane, matrix (stroma) is proteinaceous and contain DNA -een pigment chlorophyll. © Disc like structures called thy Functions: Contains chlorophyll which traps sunlight for photosynthesis. Location: Green parts of a plant/leaves b. CHROMOPLAST: ‘© Different types of coloured plastids. © Pigment Xanthophyll - yellow, Pigment Carotene Funetions: Imparts colour to fruits and flowers which helps in pollination by inseets. Location: Petals of a flower fruits ¢. LEUCOPLAST: ‘0 Colourless plastids © No pigment is present. Funetions:Storage of starch e.g. in potato 4 Anthocyanin pigment © Dissolved in cytoplasm © Blue, violet, purple colour. ‘© E.g. In beetroot, jamun, ete. NON-LIVING SUBSTANCES OR CELL. INCLUSIONS i, Granules: particles, crystals, or droplets contain © Small Fenetions! In plants contain starch, in animals contain glyeogen and fat which serve as food for the eel Vacuoles: © Clear spaces with water, minerals, sugars, etc. © Ihis bound by a membrane called tonoplast enclosing fluid called cell sap (in plant cells) ‘© Plant cells have larger vacuoles whereas animal cells haver fewer and smaller ones. Functions: © Gives turgidity to the cell © Storage of water, food, pigments and waste products.PROTOPLASM: Its the total living substances of a cell. % Itincludes cytoplasm and nucleus. Itis the physical basis of life. Itcontains water, carbohydrates, proteins, fats and mineral salts, Differences between Animal Cell and Plant Cell: ‘Animal Cell Plant Gell Cell part: Cell wall is absent Cell wall is present ‘They have small vacuoles Larger vacuoles Cell organelle: Centrosome is present Centrosome is absent Plastids are absent Plastids are present ing primitive nucleus,i.e. nucleus is not well defined(nuclear membrane is absent), E.g. bacteria, blue-green algae (cyanobacteria). Eukaryotic cell: Cells with well-defined nucleus, plants and animals ie Prokaryotic cell i.e, nucleus is surrounded by nuclear membrane. E.g i Eukaryotic cell | 1. No well-defined nucleus _ Well defined nucleus [ 2. Only a single length of nucleie acid Several lengths of genetic material called chromosomes 3. Small ribosomes Larger ribosomes 4. No other cell organelle Several cell organelles J ‘Name the organelles which show the analogy written as under: a. Transporting channels of the cell— Endoplasmic Reticulum 'b. Powerhouse of the cell— Mitochondria ©. Packaging and dispatching unit of the cell — Golgi Body 4d. Digestive bag of the eel Lysosomes €. Storage sacs of the eell— Vacuole £. Kitchen of the cell— Chloroplast 8. Control room of the cell — Nucleus ‘+ Label A to 1 Plant Cel 2 Ania el