Ch 6: Cells

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Ch 6 Cells
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History of Cytology

• 1665 Robert Hooke
• Viewed cork
• Named cells
• 1673 Anton van Leeuwenhoek
• Unicellular pond organisms named animalcules
• First to see bacteria and yeast
• 1833 Robert Brown discovered nucleus

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Cell Theory

• 1838 Matthias Schleiden
• All plant parts are composed of cells
• 1839 THeodor Schwann
• All animal tissues are composed of cells
• 1858 Rudolph Virchow
• All cells come from other cells
• Cell Theory
• 1) All living things are composed of 1 or more
  cells
• 2) Cells are the basic unit of structure and
  function
• 3) All cells are produced from existing cells

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Cells

• All cells have
• Plasma membrane (cell membrane)
• regulates materials in/out of cell
• Composed of phospholipid bilayer
• Contains different proteins
• Cytoplasm
• everything inside the cell membrane
• Medium for chemical rxns
• Cytosol fluid portion
• Chromosomes (Genes) - DNA
• Ribosomes site of protein synthesis

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Cell Size must be small

• To efficiently exchange materials in/out of cell
  membrane
• Cell surface is the only area of interaction w/
  environment
• To transport materials inside of cell
• Efficiency depends on surface area to volume
  ratio
• Small cells function more efficiently than larger
  cells!

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Surface Area to Volume Ratio
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Prokaryotic Cells

• DNA is located in nucloid region (NO NUCLEUS)
• Does not contain membrane bound organelles
• Only Eubacteria and Archeabacteria Kingdoms

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Prokaryotic Cell
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Evolution of Eukaryotic Cells

• Theory of Endosymbiosis one prokaryotic cell
  engulfed another and did not digest it, .
  Forming a double membrane successful
  relationship
• Evidence Chloroplasts and mitochondria each have
  their own separate DNA and can reproduce on their
  own, and are similar to prokaryotic cells

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Endosymbiosis
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Eukaryotic Organelles

• Nucleus contains chromosomes
• Nucleolus
• contain materials for RNA
• Makes ribosomes
• Nuclear Membrane w/ nuclear pores
• Nucleoplasm jelly like material w/in nucleus
• Mitochondria
• Powerhouse of the cell
• Releases E stored in food
• Produces ATP

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Eukaryotic Transport System

• Ribosomes site of protein synthesis
• Free floating in cytoplasm (free)
• Attached to ER (bound)
• Endoplasmic Reticulum (ER)
• An internal channel system
• Rough ER has ribosomes on surface, aids in
  transporting proteins
• Smooth ER involved in making lipids and
  breaking down toxic substances

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Eukaryotic Transport System

• Vesicles membrane buds off ER w/ proteins or
  lipids enclosed
• Lysosome contains digestive enzymes to break
  down macromolecules and worn out cell parts
• Peroxisome - contains enzymes that converts fat
  to carbohydrates (from smooth ER)
• Golgi body (complex/apparatus) packaging and
  distribution center of the cell
• Cis golgi arrival side
• Trans golgi departure side

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Cytoskeleton

• Cytoskeleton internal framework
• Mesh-like network of protein fibers
• Supports cell shape and anchors organelles
• Microtubules hollow tubes move chromosomes
  during cell division by forming centrioles
  (animal cells only)
• Actin long intertwined microfilaments that
  contract or expand to determine shape
• Intermediate fibers fibrous protein cables that
  anchor ribosomes and enzymes

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Cytoskeleton
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Cellular Movement

• Flagella long threadlike microtubules
  (whip-like tail)
• Cilia numerous short and tightly packed
  microtubules

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Intercellular Junctions

• Plants
• Plasmodesmata perforated channels in plant cell
  wall allowing cytosol, water and small solutes to
  pass freely
• Animals
• Tight junctions forms tight seal between cells
• Desmosomes anchor cells together in strong
  sheets
• Gap junctions cytoplasmic channels between
  adjacent cells allowing communication

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Animal Cells only

• Extracellular Matrix (ECM)
• Collagen strong glycoprotein fibers
• Proteoglycans network of glycoproteins
• Fibronectin attaches ECM to Integrins
• Integrins membrane proteins bound to ECM and
  interior microfilaments
• Centrioles
• composed of microtubules
• Aid in moving chromosomes during cell division
• Centrosome 2 centrioles

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Plant Cells Only

• Cell Wall
• Extra protective layer
• Cellulose - maintains structure
• Central Vacuole
• Stores water, ions, nutrients, and waste
  materials
• Controls pressure w/in cell
• Tonoplast membrane surrounding vacoule
• Chloroplast
• Contains chlorophyll photosynthetic pigment
• Uses water, carbon dioxide and sunlight to make
  food in the form of glucose

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