Cell is the Basic Unit of Life
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Cell is the Basic Unit of Life

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The word cell is derived from the Latin word “cellula” which means “a little room” ...

The word cell is derived from the Latin word “cellula” which means “a little room”
It was the British botanist Robert Hooke who, in 1664, while examining a slice of bottle cork under a microscope, found its structure resembling the box-like living quarters of the monks in a monastery, and coined the word “cells”

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Cell is the Basic Unit of Life Cell is the Basic Unit of Life Presentation Transcript

  • CELL – BASIC UNIT OF LIFE
  • CELL – BASIC UNIT OF LIFE  Prokaryotic and Eukaryotic Cells  Multicellular Organisms  Cell Membrane and Cell Wall  Cell Organelles • • • • • • Chloroplast Mitochondria Vacuoles Endoplasmic Reticulum Golgi Apparatus Nucleus  Chromosomes • Basic Structure, Number
  • D I S C OV E RY O F C E L L  In 1665 Robert Hooke – an English Scientist, Saw Cells in a thin slice of cork with his crude microscope.  He observed as “Honey – comb” like Structure and named them as CELLULAE or CELLS  His discovery indicated for the first time that living organisms consisted of number of small structures or units. Microscope
  • TO KNOW THE HISTORY OF CELL?  1665- Robert Hook discovery of cell  1674-A. Van Leeuwenhoek-studied living for the first time.  1831-Robert Brown discovery and named Nucleus in a cell  1838-39-M.J.Schleiden & Schwann formulated Cell Theory  1855-Rudolf Virchow, Stated “Omnis cellula-e-cellula” Leeuw enhoek Robert Hook Rudolf Virchow M.J.Schleiden Schwann Robert Brown
  • WHAT ARE LIVING O RG A N I S M S M A D E U P O F ?  Just as a building is made up of bricks the body of all living organisms made up of cells.  Basing on the cellular organization some organisms are made of single cells “Unicellular Organisms” e.g. Chlamydomonas, Amoeba, Paramecium  Organisms which are made up of more than a cell “multicellular”  Irrespective of unicellular or multicellular organisms the cells perform similar basic functions for their survival.
  • G A D G E T S TO S T U DY C E L L S  Cells are too small to be seen by necked eye. They are studied with the help of microscopes.  Microscopes are high resolution instruments that are used for observing fine details of very small objects  Two common types of microscopes • • Light microscope-magnification range from 100-1500 Electron microscope- magnification range from 1 lakh- 5 lakhs
  • Shape and Size of cells  Shape and size of cells vary but all of these are ultimately determined by the specific function.  Some cell can change their shapes amoeba, WBC but plants and animals have almost fixed shapes.  Smallest ell= PPLO(mycoplasma)  Largest Cell-Ostrich egg  Longest animal cell-Nerve cell  A micrometer (μm) or micron is one thousandth of a millimeter.
  • The Scale of Life
  • UNICELLULAR VS. M U LT I C E L L U L A R  Unicellular  Multicellular  Made of Single Cell  Made up of many number of cells  Single cell able to perform all the  Cells have a similar life processes like obtaining food, structure and similar basic respiration, excretion, growth and basic activities reproduction.  Cannot be divided in to cells, they life  Different shapes and aggregated to form different tissues are also called acellular organisms  Tissues form organs and organs  Amoeba, paramecium give rise to organ system that perform special function.  Plants, Animals and Fungi
  • Cell is basic unit of life  It performs all life function like intake of food materials, excretion, metabolism, respiration, irritability, etc.,  Division of Labour – Cell usually possesses a number of components called cell organelles.  Each cell organelle performs different functions • Clearing waste material • Protein synthesis • Lipid synthesis
  • What is Cell made up of ?  A cell is a tiny mass of protoplasm which is surrounded by a membrane and is capable of performing all function of life.  A typical cell is formed of three parts • Plasma membrane-to create separate environment • Nucleus-for its control • Cytoplasm-possessing metabolic machinery
  • Plasma Membrane-Cell Membrane  The outer most delicate elastic membranous covering of the cell that separates its contents from the external environment is called Plasma Membrane  Plasma Membrane is Selectively Permeable (it allows entry of certain substance restricting others)  It is made up of a bi-lipid layer and proteins are integrated in out and inside.  Small carbohydrates are attached at placed to outer surface of lipids and proteins.  Functions- Shape to contents of cell, Mechanical Barrier, Semi-Permeable, Endocytosis, Recognition Centres, Flow of Information, Osmosis, Cell Continuity, Modified to perform special functions like absorption in microvilli.
  • Plasma Membrane SEM-Plasma membrane Plasma membrane
  • Transport Across the Membrane  Membranes act as physical barriers between the organelles of a cell and its cytoplasm and its surrounding environment.  Impermeable – substances do not pass through the membrane  Permeable – both solute and solvent can pass through  Semipermeable – membrane permeable to solvent but prevents solutes passage  Selectively Permeable – if membrane allows the passage of solvent and some selected solutes.
  • Active & Passive Transport  Substances may pass across the membrane without or with expenditure of energy Active Transport - substances pass the membrane with consuming ATP  Passive Transport-substances pass the membrane without consuming ATP  Bulk Transport – Large amounts of substances and food particles across the plasma membrane  The process of bringing the bulk of materials from outside by formation of endosomes is called endocytosis.  Bulk expulsion of materials as in secretion and excretion is called exocytosis.
  • Active Transport
  • Passive Transport  Passive Transport is of two types • Diffusion • Osmosis  Diffusion – The process of movement of substances (solid, Liquid or Gas)from the region of higher concentration to the region of its lower concentration till spread uniformly in the given space is called diffusion. Diffusion – Demonstration
  • Importance of Diffusion  Helps in spread of different substances throughout cytoplasm of cell.  Osmosis is a type of diffusion where only solvent is allowed to diffuse.  Diffusion helps in exchange of respiratory gases between the cells and their environment.  Transpiration is diffusion process  Flowers spread aroma through diffusion to attract insects and other animals for pollination.
  • Osmosis  Defined as the diffusion of water or solvent across a semipermeable membrane from a region of its higher concentration to region of its lower concentration.  Plasma membrane functions as semipermeable membrane. Osmosis Osmosis - demonstration
  • How Diffusion differs from Osmosis ?  Diffusion  Osmosis  It can take place in solid,  It takes place only in liquid medium liquid and gases.  It does not involve any semi  It equalizes the concentration of substances.  Different substances diffuse independent of one another is not much influenced by the presence of other substances requires semi-permeable membrane. permeable membrane.  Diffusion  It  It does not equalize the concentration of solvent on the two sides of the membrane  Only solvent undergoes diffusion  It is influenced concentration solute particles. and by the type of
  • Types of Osmotic Solutions  Osmotic solutions are those solutions which can cause osmosis  They are three types • Hypotonic Solution, Isotonic Solution and Hypertonic Solution  Hypotonic – which has an osmotic concentration lower than another solution.  Isotonic – The solution has an osmotic concentration similar to another solution.  Hypertonic – which has an osmotic concentration higher than that of another solution.
  • Types of Osmosis  Osmosis is of two types • Endosmosis • Exosmosis  Endosmosis – Osmotic entry of water in to the cell or system  Exosmosis – Osmotic withdrawal of water from a cell or system  When we place the cell in higher concentration the water comes out of the cell by a process called exosmosis.  When we place the cell in lower concentration the water enters in to the cell by a process called endosmosis. Exosmosis Endosmosis
  • Cell Wall  Rigid, semi elastic, semi transparent and protective covering present outside the plasma membrane in plant cells, fungi and prokaryotes.  Made up of Cellulose in plants, Fungal cellulose and Chitin in fungi Plasmodesmata.  Extra deposition of lignin, suberin and cutin may be present during secondary thickening  A cementing layer called middle lamella is present between the walls of two adjacent cells  Cell wall possesses small pores through which adjacent cells Plasmodesmata. remain connected called Middle lamella.
  • What is the role of cell wall?  It provides shape to the cells  It provides mechanical strength to plants  Protects against pathogens and mechanical injury  Growth of the cell wall determines the growth of the cell  Cell wall prevents bursting of cell on endosmosis  Ability to withstand a lot of variation in nature.
  • Does cell wall & Plasma membrane are similar in function?  Cell Wall  Plasma Membrane  occurs in plant cells  Occurs in plant & animal cells  lies on the outside of the  Lies on the outside of animal cells and inside in plants cell  Rigid and thick  Flexible and thin  Cell wall is permeable  Selectively Permeable  Formed of Cellulose, Hemi  Lipids and Proteins with small number of carbohydrates cellulose and Pectin.  Provide protection strength to the cell and  Hold cellular contents and control of passage materials
  • Nucleus – The Cell Brain  Dense protoplasmic body that contains hereditary information controlling cell activities as well as for transfer to next generation  It lies in median or central position  In mature plant cell it lies towards periphery  In prokaryotes nuclear membrane is absent  It is called Nucleoid.  Cells like RBC, Sieve Elements lack Nucleus  Cells without Nucleus cannot survive for longtime  One nucleus (uninucleate) is present in most of cells but some cells may have more than one (multi nucleate)
  • What is Nucleus made up of ? Nuclear Envelop Nucleoplasm Nucleolus  Nuclear Envelop is a double membrane covering which separates the nucleus from the cytoplasm. It contains many Nuclear pores.  Nuclear materials pores allow between the exchange of nucleus and cytoplasm  Nucleoplasm – It is colorless, dense sap found inside the nucleus in which chromatin and nucleolus are suspended.  Nucleolus – a round structure found in side the nucleus, it is rich in RNA and protein. It is site of ribosome formation.
  • THE NUCLEUS IS ENCLOSED BY A DOUBLE MEMBRANE
  • Nuclear Pore Complex-Diagram
  • Does cell wall & Plasma membrane are similar in function?  Nucleus  Nucleolus  It represent the whole eukaryotic  It is a component of nucleus complex that contains genetic information  It is covered by a two membrane envelop  It controls the structure and working of cells  It is without a covering membrane  It synthesizes ribosomal subunits  Chromatin Material – An intervened mass of thread-like structure made of DNA and Proteins. During Cell Division, Chromatin becomes highly condensed, thick and rod like structures, Known as Chromosomes.
  • Chromosomes  Thread like structures which are formed by condensation of chromatin during cell division are called chromosomes they referred as hereditary vehicles  Chromosomes are made of DNA & Proteins  A chromosome consists of two similar threads called Chromatids  Two chromatids are attached at the center by a centromere  On either side of centromere chromatids are called arms
  • Chromosomes-Number  Chromosome number is fixed for each species  In most organisms they occur in homologous pair  In each pair, one chromosome belongs to father parent while other belongs to mother parent  Presence of two sets of chromosomes is called Diploid • 2n=46 ( in human)  Presence of singe set of chromosomes is called Haploid • n=23 (in human)
  • Role of Nucleus in a Cell  Nucleus contains all the genetic information not only for the cell but also the whole organism  It functions as control centre of the cell as it controls cell metabolism and cell activities  Ribosomes are formed by nucleolus part of nucleus  Nucleus us brings about cell differentiation by which a cell attains a specific structure and function.  Division of nucleus is essential for cell division  Reshuffling of chromosomes and changes in genes produce variations
  • Prokaryotes & Eukaryotes  Prokaryotes (singular ) are a group of organisms that lack a cell nucleus or any other membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus. Prokaryotes are the single-celled organisms, such as bacteria, and are roughly one micrometre in diameter.  A eukaryote is an organism whose cells contain complex structures inside the membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried Plant Cell Bacteria
  • Prokaryotes & Eukaryotes  Prokaryotes do not have a nucleus that houses its genetic material.  Prokaryote cell consists of a large DNA molecule compacted in an area of cytoplasm called the nucleoid region.  The nucleoid region is protected and encased by the cell wall, or cell membrane, the outer layering of the cell (similar to human's skin). Finally,  Flagellum a rudder-like device, affords the prokaryote the luxury of mobility.
  • Prokaryotes & Eukaryotes  Prokaryotes  Eukaryotes  Small in size, 1-10μm.  Larger in size, 5-100 μm  Organized nucleus is absent.  Organized nucleus is present  A single DNA molecule is present suspended in cytoplasm, nucleolus is absent  Membrane bound cell organelles are absent with nuclear envelop, Nucleolus is present, several DNA molecules are present  Membrane bound cell organelles are present  Typical vacuoles are absent  Typical vacuoles are present  Mitosis is absent  Mitosis is present  Bacteria, Cyanobacteria  Plants, Animals, Fungi
  • Eukaryotic (Animal ) Cell
  • Cytoplasm  The contents of a cell except for the nucleus. It includes cytosol, organelles, vesicles, and the cytoskeleton  Cytoplasm has two parts, cytosol and cell organelles  Cytosol – is the fluid part of cytoplasm, homogeneous and crystallocolloidal liquid that contains substances water, ions, enzymes, vitamins, amino acids, carbohydrates, lipids, proteins etc.,  Cell Organelles – Submicroscopic structure which are specialized to perform specific cellular functions.  Cell organelles may be bounded by a membrane as in Eukaryotes but prokaryotes lack membrane bound organelles  Virus lack cytoplasm as well as membrane
  • Endoplasmic Reticulum  The endoplasmic reticulum (ER) is a network of interconnecting membranes distributed throughout the cytoplasm.  The internal compartment, called the lumen, is a separate part of the cell with a distinct protein and ion composition.  The ER’s folding generates a surface area much greater than that of the plasma membrane.  At certain sites, the ER membrane is continuous with the outer nuclear envelope membrane.  Depending upon the presence or absence of ribosomes on the surface, there are two types of E.R.  Rough E.R. – Characterized by the presence of ribosomes on its surface  Smooth E.R. – Devoid of ribosomes on its surface
  • Endoplasmic Reticulum
  • Functions of E.R.  Protein Synthesis – Rough E.R. is the site of Protein synthesis  Lipid Synthesis – Smooth E.R. helps in lipid synthesis  Proteins and lipids synthesized on E.R. are used for making cell membrane  Transport – helps in intercellular and intracellular transport of substances  Support – it gives internal support to the cytoplasm  SER in liver cells takes part in detoxifying many poisons and drugs  SER  RER  Ribosomes are absent  Ribosomes are present  Synthesize lipids and steroids  Mainly formed of vesicles and tubules  Synthesize proteins  Formed by cisternae
  • Golgi Complex  Golgi complex is an organelle of membrane bound sacs, tubules and vesicles secrete complex biochemical  Golgi is a single complex in animal cells.  In plants they form separate units called dictyosomes.  Membrane bound sacs of Golgi are called cisternae.  Cisternae occurs in stacks, tubes and vesicles occur on their periphery
  • Golgi Apparatus
  • Functions of Golgi  Golgi apparatus is involved in repair and synthesis of cell membranes  Lysosomes are formed by Golgi apparatus  All types of substances which are to be secreted or excreted are packed in vesicles by Golgi apparatus for passage to the outside  Takes part in storage, modification and packaging of various biochemical produced by different components of the cell  Components of cell wall are synthesized by Golgi apparatus  Complex and special sugars are made by Golgi apparatus
  • Lysosomes
  • Lysosomes-suicide bags  Lysosomes generally found in animal cells they lack in plant cell  Are small spherical vesicles covered by single membrane contain digestive enzymes for intracellular digestion and waste disposal  These enzyme are synthesized by R.E.R  In damaged cell, lysosomes burst to release enzymes for digestion of cellular components  Functions  Destruction of foreign particles  Intracellular Digestion  Removal of cell debris  Time of metamorphosis  Organs are digested by Lysosomes Lysosomes-Kuffer cells
  • Mitochondria (power House of a Cell)  Mitochondria is rod-shaped cell organelles of aerobic eukaryotes which take part in the Krebs cycle.  Commonly called “Power House of the Cell” because they contain enzymes necessary for the total oxidation of food and for release of high amount of energy in the form of ATP  It is bounded by two membrane- outer membrane is smooth and porous while inner membrane is folded inwards to form Cristae  Cristae contains oxysomes they are partially embedded in inner membrane  Mitochondria enclose a matrix having DNA, ribosomes and enzymes.  DNA and ribosomes make the mitochondria semi-autonomous as they are able to manufacture some of their own proteins and enzymes.
  • Mitochondria
  • Lysosomes-suicide bags
  • Plastids  Plastids are large cell organelles found only in plant cells which are specialized to synthesize and store organic substances.  Plastids are classified on the basis of pigment present in them two types • • Leucoplasts – colorless plastids (amyloplasts, aleuroplast, elaioplasts Chromoplasts – Coloured Plastids. Green & Non green plastids  Leucoplasts  Chromoplasts (non green)  colorless  Brown or reddish in colour  Cylindrical to round in shape  Irregular in shape  Found in un exposed cells  in exposed & un exposed cell  Take part in storage of food  Do not storage food  Can change to other types  Provide coloration of organs
  • Chloroplast-kitchen of the cell  Bounded by two membranes. Inside of chloroplast is clearly marked into a colorless matrix called Stroma and Membranous system called Grana.  Each granum consists of stack of membrane bounded, flattened sacs called thylakoids  Thylakoids pigments like chlorophyll, carotenoids and phycobillins  Stroma contains enzymes for dark reaction, DNA, RNA and ribosomes, latter make the chloroplasts semiautonomous. Chloroplast Chloroplast
  • Lysosomes-suicide bags
  • Plastids-functions  Chromoplasts provide color to fruits and flowers and attract the animals to help in pollination and fruit dispersal  Leucoplasts take part in storage of protein, starch and oil  Chloroplasts trap solar energy to manufacture food through  Oxygen is being consumed in combustion and respiration. Carbon photosynthesis dioxide is being produced inn the two process. Chloroplasts maintain the balance of the two gases by absorbing carbon dioxide and oxygen in photosynthesis.
  • Ribosomes-Translation factory  Ribosomes are small rounded bodies found either in free state in the cytoplasm or attached to the surface of Endoplasmic Reticulum  They are composed of ribonucleic acid (RNA) and proteins  They are not bounded by a membrane  They are present in both prokaryotes (70s=50s+30s) eukaryotes (80s=60s+40s)  Absent in mammalian R.B.Cs.  Ribosomes are the site of protein synthesis in the cell
  • Centrosome-central apparatus  It is a small naked organelle present near the nucleus in the cells of animals and some lower plants.  It has sheath of special cytoplasm called centrosphere.  It encloses two micro cylinders called centrioles.  Two centrioles like right angles to each other.  It has nine triplet fibrils present obliquely on the periphery.  They form astral spindle fibers and produce basal bodies that form cilia and flagella
  • Vacuoles-store house of the cell  Membrane bound non-cytoplasmic sacs that contain non-living solid or liquid contents. They are of three types- sap vacuoles, food vacuoles and contractile vacuoles  Covering membrane of sap vacuole is called tonoplast  The fluid filled content of the vacuole is called cell sap or tonoplasm  Recently digestive enzymes are reported in vacuole of plant cell
  • Vacuoles-store house of the cell
  • Differences between Plant and Animal Cell  Cell wall is present  absent  Plastids are present  absent  Centrioles and centrosomes  Centrioles and centrosomes are absent are present  Vacuoles large and less  Vacuoles small and many  Nucleus lie on one side  Nucleus lies in the centre  Cell is rigid  Cell is flexible  Golgi contains dictyosomes  In the form of vesicles  Larger in size  Smaller in size  Starch is stored  Glycogen is stored
  • Plant and Animal Cell
  • Prepared by R.V.Raghavendra Rao PGTBiology JNV Kiltampalem Vizianagaram Email-raghubloom@gmail.com Phone-9490811620