M2 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


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


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


  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
  • 2 compartments: cytoplasm & karyoplasm
• 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
• Bacterial parts


  • 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, the command center of the cell
• Nuclear Envelope


  Double-layered membrane with tiny holes and nuclear lamina, 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, condenses to form chromosomes
• Chromosomes


  Contain stretches of DNA called genes, transfer hereditary information from one generation to the next
• Functions of Nucleus


  • Control all the cell activities
  • Nucleolus synthesizes ribosomes
  • Store hereditary information 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 it detoxifies drugs and poisons
• Rough ER


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


  Comprised of flattened sacs, cisternae, transports, modifies and packages proteins and lipids and prepares them for export
• Lysosomes


  Digestion compartments for cellular material that are no longer useful, filled with hydrolytic enzymes, involved in autophagy
• Peroxisomes


  Contains enzymes that primarily function to get rid of the cell of toxic substances (e.g. hydrogen peroxide)
• Mitochondria


  Rod-shaped organelles that synthesize ATP, contain their own DNA, have 2 lipid bilayer protein membranes with cristae and a matrix
• 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 cells
• Interphase


  Centrioles are duplicated, centrosome divides and pairs are split up
• Cytoskeleton


  Gives structure and shape to a cell, includes microtubules, microfilaments, and intermediate filaments
• Ribosomes


  Assemble amino acids to form proteins that are essential to carry out cellular functions, made up of ribosomal proteins and rRNA, each is composed of 2 subunits
• Plastids


  Double membrane-bound organelles found in plants and some algae, often contain different types of pigments that can change color