lesson 3.1

• Cell


  Basic structural and functional unit of living organisms
• Cell


  • Cells make up living things and carry out activities that keep a living thing alive
• Modern Cell Theory


  A collection of ideas and conclusions from many different scientists over time that describes cells and how cells operate
• Modern Cell Theory


  • All known living things are made up of one or more cells
  • All living things arise from pre-existing cells by division
  • The cell is the basic unit of structure and function in all living organisms
  • DNA is passed between cells during cell division
  • Cells of all organisms within a similar species are mostly the same
  • Energy flow occurs within cells
• Unicellular Organism


  An organism that is made up of only one cell
• Unicellular Organisms


  • Bacterium
  • Amoeba
  • Yeast
• Multicellular Organism


  An organism that is made up of more than one cell
• Multicellular Organisms


  • Plants
  • Animals
  • Insects
• Micrometer


  The unit to measure size of the cell, 1 μm = 1/1000 millimeter
• Smallest Cell


  • Mycoplasma, size: 0.1 μm
• Largest Cell


  • Ostrich egg, size: 18 cm
• Sizes of Cells in Human

  • Smallest Cell: Sperm cell, size: 5 μm
  • Largest Cell: Ovum cell, size: 120 μm
  • Longest Cell: Nerve cell, size: 1 m
• Shapes of Cells


  • Cells vary in shape, variation depends mainly upon the functions of cells
• Shapes of Cells


  • Circular Biconcave: Human RBCs
  • Branched: Nerve cell
  • No Definite Shape: Human WBCs
• Animal Cell


  • Nucleus
  • Golgi body
  • Vesicle
  • Plasma membrane
  • Mitochondria
  • Cytoskeleton
  • Centriole
  • Lysosome
  • Cytoplasm
  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum
  • Nucleolus
• Plant Cell


  • Nucleus
  • Golgi body
  • Vesicle
  • Lysosome
  • Plasma membrane
  • Mitochondria
  • Chloroplast
  • Cell wall
  • Vacuole
  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum
  • Nucleolus
• Structure of the Cell

  • All activities inside the cell and interactions of the cell with its environment are possible due to these structures and how they are organized
• Plasma Membrane


  Extremely delicate, thin, elastic, living and semi-permeable membrane, made up of two layers of lipid molecules in which protein molecules are floating
• Cell Wall


  Non living and outermost covering of a cell (plants and bacteria), can be tough, rigid and sometimes flexible, made up of cellulose, hemicellulose and pectin
• Nucleus


  Dense spherical body located near the center of the cell, wall developed in plant and animal cells, not present in bacteria and blue green algae, most cells are uninucleated, nucleus has a double layered covering called nuclear membrane with pores of diameter about 80-100 nm
• Nucleus


  Contains chromosomes, chromosomes contain stretches of DNA called genes, genes transfer the hereditary information from one generation to the next
• Cytoplasm


  Present between the plasma membrane and the nucleus, contains a clear liquid portion called cytosol and various particles, also contains many organelles with distinct structure and function
• Endoplasmic Reticulum

  Network of tubular and vesicular structures which are interconnected with one another, two types: smooth (lacks ribosomes) and rough (studded with ribosomes)
• Golgi Bodies


  Discovered by Camillo Golgi, formed by stacks of 5 to 8 membranous sacs called cisternae
• Lysosomes

  Small, spherical, single membrane sac filled with hydrolytic enzymes, occur in most animal cells and in few type of plant cell
• Vacuoles

  Single membrane sac filled with liquid or sap (water, sugar and ions), in animal cell vacuoles are temporary, small in size and few in number, in plant cell vacuoles are large and more numerous
• Mitochondria


  Small, rod shaped organelles bounded by two membranes (inner and outer), outer membrane is smooth and encloses the contents of mitochondria, inner membrane is folded in the form of shelf like inward projections called cristae, contain their own DNA which are responsible for many enzymatic actions
• Microscopy


  The detailed structure of a cell has been studied under compound light microscope (magnification at 2000x) and electron microscope (magnification at 500000x)
• Plastids


  Double membrane bound organelles found inside plants and some algae, responsible for activities related to making and storing food, often contain different types of pigments that can change the color of the cell
• Chloroplasts

  Double membrane bound organelles found mainly in plant cells, shows two distinct regions: grana (stacks of thylakoids) and stroma (a colorless dense fluid)
• Centrosome


  Consists of two structures called centrioles, centrioles are hollow, cylindrical structures made of microtubules
• Cytoskeleton

  Microtubules are hollow tubules made up of protein called tubulin, intermediate filaments are made up of several strands of fibrous proteins wound together, microfilaments are rod shaped thin filaments made up of protein called actin
• Prokaryotic Cell vs Eukaryotic Cell

  • Prokaryotic cell: Nucleus is absent, only one chromosome is present, membrane bound organelles are absent, sizes range from 0.5 to 5 μm, examples: bacteria and blue green algae
  • Eukaryotic cell: Nucleus is well developed, more than one chromosomes are present, sizes range from 5 to 100 μm, examples: all other organisms
• Animal Cell vs Plant Cell

  • Animal cell: Generally small in size, cell wall is absent, plastids are absent, vacuoles are smaller in size and less in number, centrioles are present
  • Plant cell: Generally large in size, cell wall is present, plastids are present, vacuoles are larger in size and more numerous, centrioles are absent