Module 2 Ultrastructure of the Cell

• Cell


  Functional unit of life in which all of the chemical reactions necessary for the maintenance and reproduction of life take place
• How cells are discovered

  1. Robert Hooke examined thin slices of cork and saw a network of tiny boxlike compartments

  2. Micrographia - "cells"

  3. "Cellula - little room
• Cell Theory


  • Collection of ideas and conclusions from many different scientists over time that describe cells and how cells operate
• Matthias Schleiden (1838)


  • All plant tissues are composed of cells, and an embryonic plant always arises from a single cell
• Theodore Schwann (1839)


  • All organisms consist of one or more cells
  • The cell is the basic unit of structure
• Rudolf Virchow (1855)


  • Cell arose only by the division of other preexisting cells
• Cell Theory principles


  • All organisms consist of one or more cells
  • Cell is the smallest unit of life of all living organisms
  • All cells arise only by division of a pre-existing cell
• Scientists who contributed to cell theory

  • Anton Van Leeuwenhoek (1674) - observed living cell
  • Felix Dujardin (1835) - discovered fluid content of cell
  • Robert Brown (1883) - discovered nucleus
  • JE Purkinje (1839) - named fluid content of cell as protoplasm
• Protoplasm


  The living substance of the cell
• Cytoplasm


  One of the two compartments of protoplasm
• Karyoplasm


  One of the two compartments of protoplasm
• Types of cells


  • UNICELLULAR - made of only ONE CELL (Euglena, paramecium, yeast)
  • MULTICELLULAR - made of 2 or more cells (Plants, animals, fungi)
• Prokaryote


  • Lacks nucleus and membrane-bound organelles
  • 1-10 micrometers
  • 2 kinds: bacteria and archaea
• Parts of a Bacteria cell

  • Capsule
  • Cell wall
  • Plasma membrane
  • Cytoplasm
  • Flagellum
  • Food granule
  • Plasmid (DNA)
  • Ribosomes
  • Nucleoid
  • Pili
• Eukaryote


  • Has nucleus and membrane-bound organelles
  • 10-100 micrometers
  • Unicellular (protozoa) or multicellular (plants, animals)
• Protozoa


  Single-celled eukaryotes (Paramecium, euglena, amoeba, giardia)
• 3 Basic Parts of Eukaryotic Cell

  • Plasma membrane - outer boundary
  • Nucleus - control center
  • Cytoplasm - has cytosol and organelles
• Components of Cell Membrane

  • Phospholipids - amphiphilic (hydrophilic head, hydrophobic tail)
  • Carbohydrates - glycoproteins, glycolipids
  • Protein - peripheral, integral
  • Cholesterol - regulates fluidity
• Plasma Membrane


  A semi-permeable membrane that forms the boundary between a cell's contents and the outside of the cell
• Functions of Plasma Membrane

  • Transfer of nutrients and metabolites
  • Attachment of the cell to adjacent walls
  • Communication with the external environment
• Nucleus


  • A large rounded / oval structure
  • Command center of the cell
• Nuclear Envelope


  • Double-layered membrane
  • Has tiny holes and nuclear lamina
  • It disintegrates during cell division
• Nucleoplasm


  Contains round shaped nucleolus and network of chromatin fibers
• Nucleolus


  A membrane-less organelle within the nucleus that manufactures ribosomes
• Chromatin


  Chromatin fibers take on different forms inside the nucleus
• Chromosomes


  • Contain stretches of DNA called genes
  • Genes transfer hereditary info from one gen to the next
• Nucleus


  • Control all the cell activities
  • Nucleolus synthesizes ribosomes
  • Store hereditary info in genes
• Cytoplasm


  • Present between the plasma membrane and nucleus
  • Contains a clear liquid portion called cytosol and various particles
• Summary Structure of the Cell

  • Plasma membrane
  • Nucleus
  • Cytoplasm - cytosol and organelles
• Endoplasmic Reticulum


  • Network of flattened sacs and branching tubules
  • Connected to the nuclear envelope
  • Provides a pipeline between the nucleus and cytoplasm

  
• Smooth ER


  • Synthesis of lipid substances
  • In liver cells, SER detoxify drugs and poisons
• Rough ER


  Composed of ribosomes involved in the synthesis of protein
• Golgi Apparatus


  • Comprised of flattened sacs, cisternae
  • cis face situated near the ER and trans face near the cell membrane
  • Transport, modifies and package proteins and lipids and prepares them for export
• Lysosomes


  • Digestion compartments for cellular mat that are no longer useful
  • Spherical organelles filled with hydrolytic enzymes contained by a single layer membrane
  • Autophagy - recycle the cells organic material
• Peroxisomes


  Contains a variety of enzymes (catalase) which primarily function to get rid of the cell of toxic substances (e.g. hydrogen peroxide - common byproduct of cellular metabolism)
• Mitochondria


  • Rod-shaped organelles
  • Synthesize ATP
  • Contain their own DNA
  • 2 lipid bilayer protein membranes
  • Cristae - infoldings of the inner membrane
  • Matrix contains dissolved enzymes necessary for extracting energy
• Cardiomyocytes vs Adipocytes


  Higher animals CANNOT exist without mitochondria
• Centrosome


  • Membrane-bound organelle near nucleus
  • Consist of centrioles
  • Form spindle fibres during cell division
  • Help in the formation of cilia and flagella
  • Found ONLY in animal cell
• Centrioles


  Hollow, cylindrical structures made of microtubules
• Interphase


  1. Centrioles are duplicated

  2. Centrosome divides and pairs are split up