Mitochondria

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Mitochondria

• Site of R
• 100-1000s/cell depending on tissue
• Double membrane
• Capable of division and moving w/i cell
• Invaginations of inner membrane form cristae, ?
  SA
• Fluid matrix w/i inner membrane
• Contains DNA/RNA/proteins (bacteria-like)
• Semiautonomous
• has own circular DNA
• syn. proteins
• Endosymbiotic theory
  (a.k.a. symbiogenesis)

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Peroxisomes (a.k.a. microbodies)

• Func.
• involved in photorespiration
• breakdown of fats into sucrose
• Single membrane
• Granular interior
• Associated w/ ER
• Self-replicating w/ imported
  materials

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Vacuoles

• Bound by single membrane called tonoplast (a.k.a.
  vacuolar membrane)
• Filled w/ fluid cell sap
  
• mostly water
• inorganic ions (Ca2, K, Cl-, Na, HPO42-)
• sugars, organic acids, AA
• calcium oxalate crystals
• acidic
• Single vacuole or several
• can be large portion of cell volume
• Cheap means of ? cell size

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Vacuoles

• Func.
• maint. of internal pressure (rigidity)
• rigid turgid
• storage of sugars, organic acids, proteins
• removal of toxic metabolites
• pigment deposition
• anthocyanins water soluble, responsible for
  reds/blues/purples
• breakdown of macromolecules and small organelles
• similar to lysosomes in animals

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Oil Bodies

• Spherical droplets of lipids
• Most abundant in fruits/seeds
• 45 of some seeds
• provides S to embryo
• Syn. in ER or plastids

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Ribosomes

• Small particles of protein RNA
• large small subunits
• Syn. in nucleolus,
  exported to
  cytoplasm
• Site of protein syn.
• Free in cytosol or attached to
  RER or nuclear
  envelope
• Plastids and mitochondria have own ribosomes
• Polysomes/polyribosomes cluster of ribosomes
  actively involved in protein syn.

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Endoplasmic Reticulum (ER)

• Composed of many membranes
• Lots RER in cells that store proteins
• cisternal (flattened sacs) shape
• protein syn.
• Lots of SER in cells that secrete lipids (lack
  ribosomes)
• tubular shape
• lipid syn.
• RER continuous w/ nuclear envelope
• Nuclear envelope formed from vesicles of ER
• Func.
• communication w/i cell
• channeling proteins and lipids to parts of cell
• cell-cell communication via plasmodesmata btwn
  adjacent cells

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Golgi Complex

• Golgi complex golgi bodies (a.k.a. dictyosomes)
• Stacks of 4-8 flattened sacs (cisternae) w/
  tubules at edges
• forming (cis) and maturing (trans) faces
  
• middle cisternae (medial)
• trans-Golgi network on maturing face
• Func.
• secretion (exocytosis)
• syn./secretion of CW components
• processing/secretion glycoproteins

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Endomembrane System

• Consists of Golgi/ER/PM/nuclear
  envelope/tonoplast
• New membranes arise from ER
• transition vesicles
  containing
  substances
  pinch off ER and fuse
  
  to forming face of
  Golgi
• shuttle vesicles
  transport across
  
  Golgi to maturing face
• sorting in maturing face
• secretory vesicles
  transport to final
  
  destination from
  
  maturing face

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Cytoskeleton

• Network of protein filaments throughout cytosol
• Func.
• cell division/growth/differentiation
• organelle mvmt
• Consists of actin filaments,
  intermediate
  filaments
  and microtubules

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Cytoskeleton Microtubules

• Long, thin composed of tubulin subunits arranged
  in helix
• Dynamic instability undergo breakdown and
  reformations into new configurations at specific
  pts in cell cycle
• Func.
• control alignment of cellulose during growth of
  CW
• chromosome separation (spindle fibers) and
  cell formation during
  mitosis
• direct secretory Golgi vesicles w/
  CW materials to
  CW
• mvmt of flagella/cilia

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Cytoskeleton Actin Filaments (a.k.a.
Microfilaments)

• Long, thin composed of actin subunits forming
  single fibers or bundles of fibers
• Form new configurations at pts during cell cycle
• Func.
• mvmt of nucleus during cell division
• cytoplasmic streaming
• CW deposition
• growth of tips of pollen tubes
• organelle mvmt
• vesicle secretion
• ER organization

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Flagella and Cilia

• Hairlike structures extending from cell surface
• Cilia shorter and greater in
• Flagella longer and fewer in
• func. in locomotion
• outer ring of 9 pairs of microtubules
  surrounded by 2 microtubules
  (92)
• mvmt by microtubules sliding past
  each other causes bending

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Cell Wall

• Rigid
• limits growth of protoplast, prevents rupture of
  PM
• Determines cell size/shape/tissue texture
• Func.
• defense (phytoalexins-antibiotics, lignin)
• absorption
  
• transport
  
• secretion
  
• transmission of information
  
• plant growth regulation
• Structure determines func.

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Cell Wall Composition

• Primarily composed of cellulose (subunits of
  glucose) united into long, thin
  strands (micelles)
• Micelles clump into microfibrils
• Clusters of microfibrils wind together into
  macrofibrils

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Cell Wall Composition

• Cellulose framework
• impregnated w/ matrix of noncellulosic molecules
• polysaccharides (hemicellulose/pectins) and
  glycoproteins
• hemicelluloses (i.e. xyloglucans, xylans) limit
  cell extensibility of CW by tethering
  microfibrils thus limit cell enlargement
• pectins cement first-formed wall layers of
  adjacent cells
• hydrophillic thus plastic/pliable properties to
  walls
• glycoproteins are structural proteins (i.e.
  extensin) enzymes
• extensin imparts strength

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Cell Wall Composition

• Lignin adds compressive strength bending
  stiffness (rigidity)
• found in cells w/ supportive or mechanical func.
• hydrophobic
• lignified impregnated w/ lignin
• Cutin, suberin and wax lipids
• found in outer, protective tissues
• cutin in walls of epidermis
• suberin in 2 protective tissue (i.e. cork)
• wax ? water loss

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Cell Wall Layers

• Thickness depends on func. of cell
• Walls formed from outside inward
• 1 CW 1st layer, deposited while growing
• found in living cells
• cells involved w/ wound healing/regeneration/Ps/R/
  secretion
• 1º pit fields thin area in 1º CW, location of
  plasmodesmata
• plasmodesmata cytoplasmic threads connecting
  protoplasts of adjacent cells
• Middle lamella region btwn adjacent cells
• pectin cements 1º CW of adjacent cells
• compound middle lamella 1º CW middle lamella

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Cell Wall Layers

• Other wall layers 2 wall, inside of 1º wall
• Func.
• strength
• water conduction (i.e. xylem where protoplast has
  died)
• Composed of cellulose/hemicellulose/lignin/little
  or no pectin/ proteins
• not extensible
• 3 layers
• S1 (outer), S2 (middle), S3 (inner)
• cellulose oriented differently
  in each layer
  ? strength

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Cell Wall Pits

• 2º CW laid over 1º CW but not over 1º pit fields
  thus pits formed in 2º CW
• pits opposite other pits on adjacent cells
• middle lamella 1º CW btwn adjacent cells pit
  membrane
• 2 pits pit membrane pit pair
• 2 types of pits
• simple pits no overhanging 2º wall
• border pits overhanging 2º wall

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Plasmodesmata

• Cytoplasmic strands connecting protoplast of
  adjacent cells
• Scattered throughout CW or found in pit fields
• Func.
• pathway for cell-cell transport of various
  substances

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Cell Cycle

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