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"The Fundamental Unit Of Life" Class 9

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This PPt contains chapter 5:- The Fundamental Unit of Life for Class 9 CBSE

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"The Fundamental Unit Of Life" Class 9

  1. 1. THE CELL the fundamental unit of life
  2. 2. CELLS WERE FIRST DISCOVERED BY HIM IN 1665 ROBERT HOOKE
  3. 3. ROBERT HOOKE’S MICROSCOPE
  4. 4. ROBERT OBSERVED : CORK COMES FROM THE BARK OF THE TREE HONEY COMB
  5. 5. ROBERT CALLED  THESE LITTLE COMPARTMENTS AS CELLS.  CELL IS A LATIN WORD FOR ‘ A LITTLE ROOM’.
  6. 6. COMPOUND MICROSCOPE
  7. 7. ONION PEEL 1)THESE STRUCTURES LOOK SIMILAR TO EACH OTHER. 2) TOGETHER THEY FORM A BIG STRUCTURE LIKE AN ONION BULB. 3) THE CELLS OF AN ONION PEEL WILL ALL LOOK SAME,REGARDLESS OF THE SIZE OF THE ONION. 4) THESE SMALL STRUCTURES ARE THE BASIC BUILDING UNITS OF THE ONION BULB AND ARE CALLED CELLS.
  8. 8. UNICELLULAR ORGANISMS  ORGANISMS THAT HAVE A SINGLE CELL. AMOEBA PARAMOECIUM CHLAMYDOMONAS
  9. 9. MULTICELLULAR ORGANISMS  ORGANISMS HAVING MORE THAN ONE CELL TO PERFORM VARIOUS FUNCTIONS. ANIMALS PLANTS FUNGI
  10. 10. DIFFERENT CELLS BONE CELL OVUM SPERM BLOOD CELL NERVE CELL FAT CELL
  11. 11. CELL  A cell is the smallest unit that is capable of performing life functions.
  12. 12. CELL  THE SHAPE AND SIZE OF CELLS ARE RELATED TO THE SPECIFIC FUNCTION THEY PERFORM.  EACH LIVING CEL LHAS THE CAPACITY TO PERFORM CERTAIN BASIC FUNCTIONS.  CELL CONTAINS A SPECIFIC COMPONENT CALLED ORGANELLES.  EACH KIND OF CELL ORGANELLE PERFORMS A SPECIAL FUNCTION.  ALL CELLS ARE FOUND TO HAVE THE SAME ORGANELLES,IRRESPECTIVE OF THEIR FUNCTION AND WHICH ORGANISM THEY ARE FOUND IN.
  13. 13. Why are cells of different shapes and sizes found in the human body? > The shape and size of the cells depend upon the function they perform. In a human body, each organ performs a specific function, hence the cells of different organs have different shapes and sizes.
  14. 14. Who discovered cells, and how? > Cells were first discovered by Robert Hooke, in1665. He observed a thin slice of cork under his self designed microscope.This slice of cork resembled the structure of the honeycomb consisting of small compartments. He named these small compartments as cells.
  15. 15. Why is the cell called the structural and functional unit of life? > Cell is called the structural and functional unit of life because a) It gives structure to the living organism. b) It helps the living organism to perform various life functions.
  16. 16. Cell membrane or Plasma membrane  It is the outermost covering of the cell that separates the contents of the cell from the external environment.  Allows the entry and exit of materials in and out of the cell.It also prevents the movement of some other material and is therefore called a selectively permeable membrane.  The plasma membrane is flexible and is made up of organic molecules like proteins and lipids.
  17. 17. DIFFUSION  GASEOUS EXCHANGE TAKES PLACE FROM A REGION OF HIGHER CONCENTRATION TO A REGION OF LOW CONCENTRATION.
  18. 18. OSMOSIS The movement of water from a region of high water concentration through a semi- permeable membrane to a region of low water concentration.
  19. 19. How do substances like CO2 and water move in and out the cell? Discuss. As the cell functions the concentration of CO2 in the cell increases whereas the concentration of CO2 in the external environment is low. CO2 moves out of the cell from a region of higher concentration to the external environment which is the region of lower concentration. Water moves in and out the cell from a region of higher concentration through a semi- permeable membrane to a region of lower concentration by the process of osmosis.
  20. 20. Difference between Diffusion Osmosis 1)It can occur in any medium. 2)It does not require a semi-permeable membrane. 1)It occurs only in a liquid medium. 2)It requires a semi- permeable membrane.
  21. 21. What is a hypotonic solution? Hypotonic solution is the solution surrounding the cell which has higher water concentration than that in the cell. Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net result is that the water enters the cell and the cell is likely to swell up.
  22. 22. HYPOTONIC SOLUTION
  23. 23. When is a solution said to be isotonic? When the medium surrounding a cell has the same concentration of water as that in the cell it is said to be isotonic. Water crosses the cell membrane in both the directions, but the amount going in is the same as the amount going out, so there is no overall movement of water. The cell will stay the same size.
  24. 24. ISOTONIC SOLUTION
  25. 25. What is a hypertonic solution? When the medium surrounding a cell has lower concentration of water than that in the cell it is said to be hypertonic. Water crosses the membrane in both the directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink.
  26. 26. HYPERTONIC SOLUTION
  27. 27. What is Plasmolysis? Plasmolysis is the phenomenon by which a plant cell shrinks away from the cell wall when it loses water by osmosis.
  28. 28. PLASMOLYSIS
  29. 29. What is endocytosis? Endocytosis is the process by which a cell is able to engulf food and other material from its external environment due to the flexibility of the plasma membrane. Example : Amoeba acquires its food through such processes.
  30. 30. ENDOCTYOSIS
  31. 31. Plasma membrane is called a selectively permeable membrane. Why? > Plasma membrane is called a selectively permeable membrane because it allows some materials to enter and leave the cell.
  32. 32. Cell wall >Hard outer covering of the cell. >Present outside the cell membrane. >Cell wall is composed of cellulose. >Cellulose is a complex substance and provides structural strength to plants. >Cell wall is present in the plant cell and helps the plant to withstand the environmental changes.
  33. 33. Nucleus >Has a double layered covering called nuclear membrane.  Nuclear membrane has pores which allow the transfer of material from inside the nucleus to its outside (cytoplasm).  Contains chromosomes which are visible as rod-shaped structures only when the cell is about to divide. Chromosomes contain information for inheritance of features from parents to the next generation in the form of DNA molecules. (Deoxyribo Nucleic Acid).
  34. 34. Nucleus  DNA molecules contain information necessary for constructing and organising cells.  Functional segments of DNA are called genes.  When the cell is not dividing, DNA is present as a part of the chromatin material. Chromatin material is visible as entangled mass of thread like structures. Whenever the cell is about to divide , the chromatin material gets organised into chromosomes.  Plays an important role in cellular reproduction.  It helps in determining the way the cell will develop and what form it will exhibit on maturity by directing the chemical activites of the cell.
  35. 35. Haploid Cell  The cell having one set of chromosome (n number of chromosome).  Gametes or sex cells (Sperm and Ova) are the example.  They are formed as a result of meiosis.  They fertilize to form to form offsprings (which are diploid)  eg. Human Sperm cell/ Ova cell (23 number of chromosome: n)
  36. 36. Diploid Cell  The cell having two sets of chromosome (2n Chromosome)  Somatic cells have diploid set of chromosome.  Diploid cell reproduce by mitosis.  eg. Human Muscle cell or blood cell (46 number of chromosome: 2n (2 x 23 = 46))
  37. 37. Significance of membranes  Example : Viruses  Viruses lack any membranes and hence do not show any characteristics of life until they enter a living body and use its cell machinery to multiply.
  38. 38. Cytoplasm • It is the fluid content inside the plasma membrane. • Contains specialised cell organelles.
  39. 39. Cell organelles 1) Endoplasmic reticulum 2) Golgi apparatus 3) Lysosomes 4) Mitochondria 5) Plastids 6) Vacuoles
  40. 40. Endoplasmic Reticulum  ER is a large network of membrane bound tubes and sheets.  Extends throughout cytoplasm  Two types - Rough Endoplasmic Reticulum (RER) Smooth Endoplasmic Reticulum (SER)  Serves as channels for the transport of materials between various regions of the cytoplasm or between the cytoplasm and the nucleus.  Functions as a cytoplasmic framework providing a surface for biochemical activities.
  41. 41. RER  Arranged into flattened sacs  Ribosomes on surface give it a rough appearance  Ribosomes are the sites of protein synthesis.  Cells that specialize in secreting proteins have lots of rough ER
  42. 42. SER  A series of interconnected tubules .  No ribosomes on surface.  Helps in the manufacture of fat molecules or lipids.  In liver cells of vertebrates, SER detoxifies many poisons and drugs.
  43. 43. Membrane Biogenesis  It is the process of formation of the cell membrane from proteins and lipids.
  44. 44. GOLGI APPARATUS First discovered by Camillo Golgi.  It consist of a system of membrane- bound vesicles arranged parallel to each other in stacks called cisterns.  The material synthesised near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus.  Its functions include storage , modification and packaging of products in vesicles. Involved in the formation of the lysosome.
  45. 45. LYSOSOMES >Waste disposal system of the cell. Keep the cell clean by digesting any foreign material as well as worn out cell organelles.  Contain powerful digestive enzymes capable of breaking down all organic material. When the cell gets damaged, lysosomes may break open and the enzymes digest their own cell. Thus known as suicide bags of a cell.
  46. 46. Mitochondria Known as the powerhouse of the cell.  The energy required for various chemical activities is released by the mitochondria in the form of ATP molecules.( Adenosine triphosphate). ATP is known as the energy currency of the cell.  Mitochondria have two membrane coverings.  Outer membrane is very porous. Inner membrane is deeply folded. Mitochondria are able to make their own proteins as they have their own DNA and ribosomes .
  47. 47. Plastids  Present in plant cells.  Two types- 1) Chromoplasts (coloured) 2) Leucoplasts (colourless) > Plastids containing green pigment chlorophyll are called Chloroplasts.  Leucoplasts store materials as starch, oils and protein granules.  Plastids contain membrane layers embedded in a material called stroma.  Has a similar structure like the mitochondria.  Have their own DNA and ribosomes.
  48. 48. CHLOROPLASTS
  49. 49. Vacuoles  Storage sac for solid or liquid contents.  Small size vacuoles are present in animals.  Large in plants.  In plant cells, vacuoles are full of cell sap and provide turgidity and rigidity to the cell.  Vacuoles store amino acids, sugars, various organic acids and some proteins.  In Amoeba, the food vacuole contains the food items that the Amoeba has consumed.  Vacuoles play an important role in expelling excess water and some wastes from the cell.
  50. 50. Ribosomes  Are dense, spherical and granular particles.  Present freely in matrix (Cytosol) or remain attached to the RER.  Major constituents is RNA and Proteins.  Not bounded by membrane.  Present in both prokaryotic and eukaryotic cell except mammalian RBC.  Function- Important role in Protein synthesis.
  51. 51. Peroxisomes  Are small and spherical organelles containing powerful oxidative enzymes.  Mostly found in kidney and Liver cells.  Present in both plants and animal cell.  Functions: Specialized for carrying out some oxidative reaction such as detoxifications or removal of toxic substance from the cell.
  52. 52. Centrosome  Found only in animal cell.  Consists of two granule, like – Centriole.  Centrioles are hollow and cylindrical structures which are made up of microtubules.  In plant cell, Polar caps perform the function of centrioles.  Function:- Centrosome helps on cell division in animal cell. During cell division centrioles migrate to the poles of animal cell and are involved in spindle formation.  In plant cell, cell division involves polar caps for the spindle formation.
  53. 53. Plasmodesmata  Are microscopic channel which traverse the cell wall of plant cell and some algal cell, enabling transport and communication between them.  channel through the cell wall that allows molecules and substances to move back and forth as needed.  Found only in Plant cell.
  54. 54. Cell Division  Process by which cell divides into two or more daughter cells.  By three process: Binary Fission, Mitosis and Meiosis
  55. 55. Overview of a plant cell
  56. 56. Overview of an animal cell
  57. 57. Active Transport  movement of dissolved molecules into or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration.  The particles move against the concentration gradient, using energy released during respiration.  Sometimes dissolved molecules are at a higher concentration inside the cell than outside, but, because the organism needs these molecules, they still have to be absorbed.  Carrier proteins pick up specific molecules and take them through the cell membrane against the concentration gradient.
  58. 58. Types of Active transport  There are two types of active transport namely – Primary active transport and secondary active transport.  Primary active transport  In this process of transportation, the energy is utilized by the breakdown of the ATP – Adenosine triphosphate to transport molecules across the membrane against a concentration gradient. Therefore, all the groups of ATP powered pumps contain one or more binding sites for the ATP molecules, which are present on the cytosolic face of the membrane. Basically, the primary active transport uses external chemical energy such as the ATP.  Sodium-potassium pump, the most important pump in the animal cell is considered as an example of primary active transport. In this process of transportation, the sodium ions are moved to the outside of the cell and potassium ions are moved to the inside of the cell.
  59. 59.  Secondary active transport  Secondary active transport is a kind of active transport that uses electrochemical energy. It takes place across a biological membrane where a transporter protein couples the movement of an electrochemical ion (typically Na+ or H+) down its electrochemical gradient to the upward movement of another molecule or an ion against a concentration or electrochemical gradient.
  60. 60. Examples of active transport include:  Phagocytosis of bacteria by Macrophages.  Movement of Ca2+ ions out of cardiac muscle cells.  Transportation of amino acids across the intestinal lining in the human gut.  Secretion of proteins like enzymes, peptide hormones, and antibodies from different cells.  Functioning of the White Blood Cells by protecting our body by attacking diseases causing microbes and other foreign invaders.  uptake of glucose by epithelial cells in the villi of the small intestine
  61. 61. Diffusion Osmosis Active transport Down a concentration gradient ✓ ✓ ✗ Against a concentration gradient ✗ ✗ ✓ Energy needed ✗ ✗ ✓ Substance moved Dissolved solutes Water Dissolved solutes Notes Gases and dissolved gases also diffuse Partially permeable membrane needed Carrier protein needed Active transport vs diffusion and osmosis
  62. 62. Active Transport in Plants  Like humans and animals, plants also require transport systems which are mainly involved in the transport of materials, such as water, minerals, and necessary nutrients to all parts of the plant for its survival.  Active transport is a mode of transportation in plants, which uses stored energy to move the particles against the concentration gradient. In a plant cell, it takes place in the root cells by absorbing water and minerals. Active transport always leads to accumulation of molecules are ions towards one side of the membrane. This mode of transportation in plants is carried out by membrane proteins and transports the substance from the lower concentration to higher concentration.
  63. 63. Passive Transport  It is the biological process of movements of the biochemical across the cell membranes and tissues.  natural phenomenon, which does not require any external energy.
  64. 64. Types of Passive Transport 1. Simple Diffusion 2. Facilitated Diffusion 3. Filtration 4. Osmosis
  65. 65. 1. Simple Diffusion  movement of substances from a region of higher concentration to lower concentration.  The difference in the concentration of the two areas is termed as concentration gradient and the process of diffusion continues until this gradient neutralizes.  Diffusion occurs in liquid and gases because their particles move randomly from one place to another.  It is an important process in living things required for different life processes. The substances move in and out of the cells by simple diffusion.
  66. 66. 2. Facilitated Diffusion  Passive transportation of ions or molecules across the cell membrane through specific transmembrane integral proteins.  The molecules, which are large and insoluble require a carrier substance for their transportation through the plasma membrane.  This process does not require any cellular or external energy.  Glucose transporter, ion channels and aquaporins are some of the examples of facilitated diffusion.  The cell membrane is permeable only to a few molecules that are smaller in size and non-polar.  Therefore, facilitated diffusion with the help of transmembrane proteins is important.
  67. 67. 3. Filtration  Process of separating solids from liquids and gases.  The selective absorption of nutrients in the body is an example of filtration.  This process does not require any energy and takes place along the concentration gradient.  In the process of filtration, the cell membrane permits only those substances which are soluble and could easily pass through its pores.  The kidneys are an example of a biological filter. The blood is filtered by the glomerulus and the necessary molecules are reabsorbed.
  68. 68. 4. Osmosis  water and other molecules pass through a selectively permeable membrane in order to balance the concentration of other substances.  Osmosis is affected by the concentration gradient and temperature. The greater the concentration gradient, the faster is the rate of osmosis. Also, the rate of osmosis increases with the increase in temperature.
  69. 69. Examples Of Passive Transport  Ethanol enters our body and hits the bloodstream. This happens because the ethanol molecules undergo simple diffusion and pass through the cell membrane without any external energy.  Reabsorption of nutrients by the intestines by separating them from the solid waste and transporting the nutrients through the intestinal membrane into the bloodstream.  When a raisin is soaked in water the water moves inside the raisin by the process of osmosis and it swells.
  70. 70. Active Transport Passive Transport Requires cellular energy. Do not require cellular energy. It circulates from an area of lower concentration to a region of higher concentration It circulates from a region of higher concentration to a region of lower concentration Required in the transportation of all the molecules such as proteins, large cells, complex sugars, ions, etc. Required in the transportation all the soluble molecules which include oxygen, water, carbon dioxide, lipids, sex hormones, monosaccharides, etc. It transports various molecules in the cell. It is involved in the maintenance of the equilibrium level inside the cell. Active transport is a dynamic process. Passive Transport is a physical process. It is highly selective. It is partly non-selective Active transport is a rapid process. Passive transport is a comparatively slow process. Transpires in one direction. Transpires bidirectionally. Active transportation is influenced by temperature. Passive transportation is not influenced by temperature. In Active transport carrier proteins are required In passive transport carrier proteins are not required This process reduces or halts as the oxygen content level is reduced. This process is not affected by the level of oxygen content. Metabolic inhibitors can influence and stop the active transport. Passive transportation is not influenced by metabolic inhibitors. Different types of Active Transport are – Exocytosis, endocytosis, sodium-potassium pump Different types of Passive Transport are – Osmosis, diffusion, and facilitated diffusion
  71. 71. Can you name the two organelles we have studied that contain their own genetic material? Ans : Mitochondria and plastids are the two organelles that contain their own genetic material. Both these organelles have their own DNA and ribosomes.
  72. 72. Make a comparison and write down ways in which plant cells are different from animal cells. Animal cell Plant cell Animal cells are generally small in size. Plants cells are usually larger than animal cells. Cell wall is absent. Cell wall is present. Except the protozoan Euglena, no animal cell possesses plastids. Plastids (chromoplasts and leucoplasts) are present. Vacuoles are smaller in size. Vacuoles are larger in size.
  73. 73. What would happen to the life of a cell if there was no Golgi apparatus?  (i) Membranes of the Golgi apparatus are often connected to ER membranes. It collects simpler molecules and combines them to make more complex molecules. These are then packaged in small vesicles and are either stored in the cell or sent out as per the requirement. Thus, if the Golgi apparatus is absent in the cell, then the above process of storage, modification, and packaging of products will not be possible.  (ii) The formation of complex sugars from simple sugars will not be possible as this takes place with the help of enzymes present in Golgi bodies.  (iii) The Golgi apparatus is involved in the formation of lysosomes. Thus, if the Golgi body is absent in a cell, the synthesis of lysosomes will not be possible in the cell.
  74. 74. Which organelle is known as the powerhouse of the cell? Why?  Mitochondria are known as the powerhouse of cells. Mitochondria create energy for the cell, and this process of creating energy for the cell is known as cellular respiration. Most chemical reactions involved in cellular respiration occur in the mitochondria. The energy required for various chemical activities needed for life is released by the mitochondria in the form of ATP (Adenosine triphosphate) molecules. For this reason, mitochondria are known as the powerhouse of cells.
  75. 75. Where do the lipids and proteins constituting the cell membrane get synthesized? Lipids and proteins constituting the cell membrane are synthesized in the endoplasmic reticulum. 1)SER (Smooth endoplasmic reticulum) helps in the manufacturing of lipids. 2)RER (Rough endoplasmic reticulum) has particles attached to its surface, called ribosomes. These ribosomes are the site for protein synthesis.
  76. 76. How does an Amoeba obtain its food?  Amoeba obtains its food through the process of endocytosis. The flexibility of the cell membrane enables the cell to engulf the solid particles of food and other materials from its external environment.
  77. 77. What is osmosis?  The movement of water molecules from a region of high concentration to a region of low concentration through a selectively permeable membrane is called osmosis.
  78. 78. THANKS!!!!!!!!!

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