A Tour of the Cell

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A Tour of the Cell

• Chapter 6

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Microscopes windows to the world of the cell

• Cells are the basic unit of life.
• The invention and improvement of microscopes in
  the 17th century led to the discovery and early
  study of cells
• Robert Hooke observed cells in a slice of cork

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History of Cells
1800s Schwann Animal tissues are composed of
cells Schleiden Plant materials are composed
of cells Virchow - All tissues from living
organisms are composed of cells
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The Cell Theory

• All living things are composed of cells
• Cells are basic units of structure and function
• All cells come from pre-existing cells

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HOW CELLS ARE STUDIED

• Microscopy
• Cell Fractionation

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Overview of Cells

• Plasma Membrane
• Nucleus / Nuclear region
• Cytoplasm.
• Cell Wall

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The Eukaryotic Animal Cell
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The Eukaryotic Plant Cell
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Major type of Cells

• There are two basic types of cells
• Prokaryotic Eukaryotic
• A major difference between prokaryotic and
  eukaryotic cells is the location of chromosomes.

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Prokaryotic Cells

• Lacks a nucleus and most other organelles
• DNA concentrated in nucleoid region
• Bacteria and Archae
• 1-10 micrometers
• Appear earliest in earths fossil record

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Eukaryotic Cells

• Nucleus surrounded by its membrane
• Internal organelles bounded by membranes
• 10 100 micrometers
• Protists, Fungi, Plants, Animals

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Membranes organize a cells activities

• Section 6.2

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Plasma Membrane

• Boundary that separates the interior of a living
  cell from its surroundings and regulates the
  traffic of chemicals into and out of the cell
• Phospholipid Bilayer
• Protein icebergs float in a sea of
  phospholipids

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Phospholipid Molecule

• Composed of proteins and a type of lipid called
  phosopholipid (glycerol2 fatty acids)

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Protein icebergs in a sea of phospholipids
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Plasma Membrane
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Functions of Membrane Proteins

• Enzymes
• Cell-Cell Recognition
• Cell Signaling
• Transport

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Enzyme Activity
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Cell-Cell Recognition
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Cell Signaling
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Transport of Materials
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Membranes Regulate Traffic of Molecules

• Section 6.3

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Function of Cell Membranes

• Materials need to move in and out of the cell
• Function like gatekeepers, letting some molecules
  through, but not others ? Selectively Permeable

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Types of Transport

• Diffusion
• Passive Transport
• Facilitated Transport
• Active Transport

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Diffusion

• The spread of molecules from areas of high
  concentration, to areas of low concentration.
• EQUILIBRIUM ?when the molecules are even
  throughout a space Concentration Gradient ?
  difference between concentrations in a space.

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Passive Transport

• Diffusion Some substances are allowed to move
  freely

• Facilitated diffusion? transport proteins

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Osmosis

• The diffusion of water (across a membrane)
• Water will move in the direction where there is a
  high concentration of solute and low water
  concentration

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Osmosis

• Dissolved molecules ( ions, organic molecules,
  etc) are called solutes
• Most solutes cannot cross membranes
• As solute conc increases free H2O decreases
• Hypertonic? high solute
• Hypotonic ? low solute

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Isotonic- means the same
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Hypotonic- less solute
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Hypertonic- high solute
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Water Balance in Animal Cells

• Net water flow into the cell which can burst
  (Hemolysis)

• Water flow equal in both directions

Net water flow out of cell which
shrinks (Crenation)
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Water Balance in Plant Cells

• Turgid Flaccid

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Plasmolysis

• Shrinking of cytoplasm in both plant and animal
  cells

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Active Transport

• Cell expends energy to move molecules or ions
  across the membrane
• A specific transport protein pumps solute across
  a membrane
• The chemical energy is supplied by the
  mitochondria
• Example Na(Sodium) K(Potassium) pump.

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Active Transport
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Transport of Large Molecules

• Large molecules have to be packaged to be
  transported in and out of the cell
• Vesicles (membranes sacs) are formed to move the
  substances
• Exocytosis
• Endocytosis

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Exocytosis Ednocytosis
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More Exo Endo
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Cell Organelles

• Section 6.4

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Nucleus contents
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Endoplasmic Reticulum (rough smooth)
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Ribosome
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Protein Synthesis
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Golgi Body
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Lysosomes
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Chloroplasts and Mitochondria energize cells

• The cellular machinery constantly needs energy to
  function.
• Supplied by two organelles the Chloroplasts
  Mitochondria

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Chloroplasts
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Mitochondria
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The Internal Skeleton

• Cytoskeleton
• Flagella
• Cilia

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Microfilaments
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Centriole
Cilia
Microtubule