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Tour of the Cell
 

Tour of the Cell

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    Tour of the Cell Tour of the Cell Presentation Transcript

    • A Tour of the Cell
      Tour Guide…
      Mrs. Erin Fortenberry
    • Question ?
      Can cells be seen with the naked eye?
      Yes, a few are large enough, but most require the use of a microscope.
    • Microscope History
      1590 - Janseen Brothers invent the compound microscope.
      1665 - Robert Hooke “discovers” cells in cork.
      Early 1700’s - von Leeuwenhoek makes many observations of cells including bacteria.
    • Light Microscope - LM
      Uses visible light to illuminate the object.
      Relatively inexpensive type of microscope.
      Can examine live or dead objects.
    • Electron Microscopes
      Use beams of electrons instead of light.
      Invented in 1939, but not used much until after WWII.
    • TEM
      SEM
    • Advantages
      Much higher magnifications.
      Magnifications of 50,000X or higher are possible.
      Can get down to atomic level in some cases.
    • Disadvantages
      Need a Vacuum.
      Specimen must stop the electrons.
      High cost of equipment.
      Specimen preparation.
    • Cell Biology or Cytology
      Cyto = cell
      - ology = study of
    • History of Cells
      Robert Hooke - Observed cells in cork.
      Coined the term "cells” in 1665.
    • History of Cells
      1833 - Robert Brown, discovered the nucleus.
      1838 - M.J. Schleiden, all plants are made of cells.
      1839 - T. Schwann, all animals are made of cells.
    • Cell Theory
      All living matter is composed of one or more cells.
      The cell is the structural and functional unit of life.
    • Types of Cells
      Prokaryotic - lack a nucleus and other membrane bounded structures.
      Eukaryotic - have a nucleus and other membrane bounded structures.
    • Prokaryotic
      Eukaryotic
      Nucleus
    • Basic Cell Organization
      Membrane
      Nucleus
      Cytoplasm
      Organelles
    • AnimalCell
    • Plant Cell
    • Membrane
      Separates the cell from the environment.
      Boundary layer for regulating the movement of materials in/out of a cell.
    • Cytoplasm
      Cell substance between the cell membrane and the nucleus.
      The “fluid” part of a cell. Exists in two forms:
      gel - thick
      sol - fluid
    • Organelle
      Term means "small organ” Formed body in a cell with a specialized function.
      Important in organizational structure of cells.
    • Organelles - function
      Way to form compartments in cells to separate chemical reactions.
      Keeps various enzymes separated in space.
    • Nucleus
      Most conspicuous organelle.
      usually spherical, but can be lobed or irregular in shape.
    • Structure
      Nuclear membrane
      Nuclear pores
      Nucleolus
      Chromatin
    • Nuclear Membrane
      Double membrane separated by a 20-40 nm space.
      Inner membrane supported by a protein matrix which gives the shape to the nucleus.
    • Nuclear Pores
      Regular “holes” through both membranes.
      100 nm in diameter.
      Protein complex gives shape.
      Allows materials in/out of nucleus.
    • Nucleolus
      Dark staining area in the nucleus.
      0 - 4 per nucleus.
      Storage area for ribosomes.
    • Chromatin
      Chrom: colored
      - tin: threads
      DNA and Protein in a “loose” format. Will form the cell’s chromosomes.
    • Nucleus - Function
      Control center for the cell.
      Contains the genetic instructions.
    • Ribosomes
      Structure: 2 subunits made of protein and rRNA.
      No membrane.
      Function: protein synthesis.
    • Locations
      Free in the cytoplasm - make proteins for use in cytosol.
      Membrane bound - make proteins that are exported from the cell.
    • Endomembrane System
      Membranes that are related through direct physical continuity or by the transfer of membrane segments called vesicles.
    • Endomembrane System
    • Endoplasmic Reticulum
      Often referred to as ER.
      Makes up to 1/2 of the total membrane in cells.
      Often continuous with the nuclear membrane.
    • Structure of ER
      Folded sheets or tubes of membranes.
      Very “fluid” in structure with the membranes constantly changing size and shape.
    • Types of ER
      Smooth ER: no ribosomes.
      Used for lipid synthesis, carbohydrate storage, detoxification of poisons.
      Rough ER: with ribosomes.
      Makes secretory proteins.
    • Golgi Apparatus
      Structure: parallel array of flattened cisternae. (looks like a stack of Pita bread)
      3 to 20 per cell.
      Likely an outgrowth of the ER system.
    • Function of Golgi Bodies
      Processing - modification of ER products.
      Distribution - packaging of ER products for transport.
    • Golgi Vesicles
      Small sacs of membranes that bud off the Golgi Body.
      Transportation vehicle for the modified ER products.
    • Cell-On-The-Ceiling Project
    • Lysosome
      Single membrane.
      Made from the Golgi apparatus.
    • Function
      Breakdown and degradation of cellular materials.
      Contains enzymes for fats, proteins, polysaccharides, and nucleic acids.
      Over 40 types known.
    • Lysosomes
      Important in cell death.
      Missing enzymes may cause various genetic enzyme diseases.
    • Vacuoles
      Structure - single membrane, usually larger than the Golgi vesicles.
      Function - depends on the organism.
    • Protists
      Contractile vacuoles - pump out excess water.
      Food vacuoles - store newly ingested food until the lysosomes can digest it.
    • Plants
      Large single vacuole when mature making up to 90% of the cell's volume.
      Tonoplast - the name for the vacuole membrane.
    • Function
      Water regulation.
      Storage of ions.
      Storage of hydrophilic pigments. (e.g. red and blues in flower petals).
    • Function: Plant vacuole
      Used to enlarge cells and create turgor pressure.
      Enzymes (various types).
      Store toxins.
      Coloration.
    • Microbodies
      Structure: single membrane.
      Often have a granular or crystalline core of enzymes.
    • Function
      Specialized enzymes for specific reactions.
      Peroxisomes: use up hydrogen peroxide.
      Glyoxysomes: lipid digestion.
    • Enzymes in a crystal
    • Mitochondria
      Structure: 2 membranes. The inner membrane has more surface area than the outer membrane.
      Matrix: inner space.
      Intermembrane space: area between the membranes.
    • Inner Membrane
      Folded into cristae.
      Amount of folding depends on the level of cell activity.
      Contains many enzymes.
      ATP generated here.
    • Function
      Cell Respiration - the release of energy from food.
      Major location of ATP generation.
      “Powerhouse” of the cell.
    • Mitochondria
      Have ribosomes.
      Have their own DNA.
      Can reproduce themselves.
      May have been independent cells at one time.
    • Chloroplasts
      Structure - two outer membranes.
      Complex internal membrane.
      Fluid-like stroma is around the internal membranes.
    • Inner or Thylakoid Membranes
      Arranged into flattened sacs called thylakoids.
      Some regions stacked into layers called grana.
      Contain the green pigment chlorophyll.
    • Function
      Photosynthesis - the use of light energy to make food.
    • Chloroplasts
      Contain ribosomes.
      Contain DNA.
      Can reproduce themselves.
      Often contain starch.
      May have been independent cells at one time.
    • Plastids
      Group of plant organelles.
      Structure - single membrane.
      Function - store various materials.
    • Cytoskeleton
      Network of rods and filaments in the cytoplasm.
    • Functions
      Cell structure and shape.
      Cell movement.
      Cell division - helps build cell walls and move the chromosomes apart.
    • Components
      Microtubules
      Microfilaments
      Intermediate Filaments
    • Microtubules
      Structure - small hollow tubes made of repeating units of a protein dimer.
      Size - 25 nm diameter with a 15 nm lumen. Can be 200 nm to 25 mm in length.
    • Tubulin
      Protein in microtubules.
    • Microtubules
      Regulate cell shape.
      Coordinate direction of cellulose fibers in cell wall formation.
      Tracks for motor molecules.
    • Microtubules
      Form cilia and flagella.
      Internal cellular movement.
      Make up centioles, basal bodies and spindle fibers.
    • Cilia and Flagella
      Cilia - short, but numerous.
      Flagella - long, but few.
      Function - to move cells or to sweep materials past a cell.
    • Movie
    • Centrioles
      Usually one pair per cell, located close to the nucleus.
      Found in animal cells.
      9 sets of triplet microtubules.
      Help in cell division.
    • Basal Bodies
      Same structure as a centriole.
      Anchor cilia and flagella.
    • Microfilaments
      5 to 7 nm in diameter.
      Structure - two intertwined strands of actin protein.
    • Microfilaments are stained green.
    • Functions
      Muscle contraction.
      Cytoplasmic streaming.
      Pseudopodia.
      Cleavage furrow formation.
      Maintenance and changes in cell shape.
    • Intermediate Filaments
      Fibrous proteins that are super coiled into thicker cables and filaments 8 - 12 nm in diameter.
      Made from several different types of protein.
    • Functions
      Maintenance of cell shape.
      Hold organelles in place.
    • Cytoskeleton
      Very dynamic; changing in composition and shape frequently.
      Cell is not just a "bag" of cytoplasm within a cell membrane.
    • Cell Wall
      Nonliving jacket that surrounds some cells.
      Found in:
      Plants
      Prokaryotes
      Fungi
      Some Protists
    • Plant Cell Walls
      All plant cells have a Primary Cell Wall.
      Some cells will develop a Secondary Cell Wall.
    • Primary Wall
      Thin and flexible.
      Cellulose fibers placed at right angles to expansion.
      Placement of fibers guided by microtubules.
    • Secondary Wall
      Thick and rigid.
      Added between the cell membrane and the primary cell wall in laminated layers.
      May cover only part of the cell; giving spirals.
      Makes up "wood”.
    • Middle Lamella
      Thin layer rich in pectin found between adjacent plant cells.
      Glues cells together.
    • Cell Walls
      May be made of other types of polysaccharides and/or silica.
      Function as the cell's exoskeleton for support and protection.
    • Extracellular Matrix - ECM
      Fuzzy coat on animal cells.
      Helps glue cells together.
      Made of glycoproteins and collagen.
      Evidence suggests ECM is involved with cell behavior and cell communication.
    • Intercellular Juctions
      Plants-Plasmodesmata
    • Plasmodesmata
      Channels between cells through adjacent cell walls.
      Allows communication between cells.
      Also allows viruses to travel rapidly between cells.
    • Intercellular Juctions
      Animals:
      Tight junctions
      Desmosomes
      Gap junctions
    • Tight Junctions
      Very tight fusion of the membranes of adjacent cells.
      Seals off areas between the cells.
      Prevents movement of materials around cells.
    • Desmosomes
      Bundles of filaments which anchor junctions between cells.
      Does not close off the area between adjacent cells.
      Coordination of movement between groups of cells.
    • Gap Junctions
      Open channels between cells, similar to plasmodesmata.
      Allows “communication” between cells.