A Tour of the Cell

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• A Tour of the Cell

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Cytology science/study of cells

• Light microscopy
• resolving power measure of clarity
• Electron microscopy
• TEM (transmission) electron beam to study cell
  ultrastructure
• SEM (scanning) electron beam to study cell
  surfaces
• Cell fractionation cell separation organelle
  study
• Ultracentrifuges cell fractionation 130,000
  rpm

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Cell Types Prokaryotic

• Nucleoid region DNA concentration
• No organelles with membranes
• Ribosomes protein synthesis
• Plasma membrane (all cells) semi-permeable
• Cytoplasm/cytosol (all cells)

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Prokaryote vs. eukaryote

• Eukaryote
• More complicated
• Has membrane bound organelles
• DNA is stored in the nucleus of the cell
• Double helix
• Bound to histone proteins
• Ribosomes are attached to rough ER
• Make proteins and enzymes

• Prokaryote
• Less complex (generally bacteria)
• Has plasma membrane
• May have cell wall
• May have some photosynthetic material
• Does not have membrane bound organelles
• DNA is not bound (circular)
• Has ribosomes (not attached to ER)
• Have proteins and enzymes
• Have mitochondria

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Cell size

• As cell size increases, the surface area to
  volume ratio decreases
• Rates of chemical exchange may then be inadequate
  for cell size
• Cell size, therefore, remains small

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Composite Animal Cell
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Flagella
Nuclear envelope
nucleolus
Nucleus
Chromosomes
Lysosome
Ribosomes
Endoplasic reticulum
Microtuble
Mitochondrion
Golgi apparatus
Plasma membrane
Centrioles
Cillia
Composite Animal Cell
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Next quiz

• For the quiz, you MUST know the parts of the cell
  for both the plant and animal cell
• See pp. 100-101 in your text

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Nucleus

• Genetic material...
• chromatin
• chromosomes
• nucleolus rRNA ribosome synthesis
• Double membrane envelope with pores
• Protein synthesis (mRNA)

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Nucleolus

• Located within the nucleus
• Primarily responsible for the production of
  ribosomes
• The different subunits are created within the
  nucleolus and then transported out of the
  nucleolus to be assemble along the endoplasmic
  reticulum (ER)
• This makes this portion of the ER the rough ER

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Ribosomes

• Protein manufacturing
• Free
• cytosol
• protein function in cell
• Bound
• endoplasmic reticulum
• membranes, organelles

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Endomembrane system, I

• Endoplasmic reticulum (ER)
• Continuous with nuclear envelope
• Smooth ER no ribosomes
  synthesis of lipids,
• metabolism of carbohydrates detoxification of
  drugs and poisons
• Rough ER with ribosomes synthesis of
  secretory proteins (glycoproteins), membrane
  production

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Endomembrane system, II

• Golgi apparatus
• ER products are modified, stored, and then
  shipped
• Cisternae flattened membranous sacs
• trans face (shipping) cis face (receiving)
• Transport vesicles

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Endomembrane system, III

• Lysosomes
• sac of hydrolytic enzymes digestion of
  macromolecules
• Phagocytosis
• Autophagy recycle cells own organic material
• Tay-Sachs disease lipid-digestion disorder

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Endomembrane system, IV

• Vacuoles
• membrane-bound sacs (larger than vesicles)
• Food (phagocytosis)
• Contractile (pump excess water)
• Central (storage in plants)

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Other membranous organelles

• Mitochondria
• quantity in cell correlated with metabolic
  activity
• cellular respiration
• double membranous (phospholipid)
• cristae/matrix
• intermembrane space
• contain own DNA

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Other membranous organelles

• Chloroplast
• type of plastid
• double membranous
• thylakoids (flattened disks)
• grana (stacked thylakoids)
• stroma
• own DNA

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Peroxisomes

• Single membrane
• Produce hydrogen peroxide in cells
• Metabolism of fatty acids detoxification of
  alcohol (liver)
• Hydrogen peroxide then converted to water

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The Cytoskeleton end here

• Fibrous network in cytoplasm
• Support, cell motility, biochemical regulation
• Microtubules
• thickest
• tubulin protein
• shape, support, transport, chromosome
  separation
• Microfilaments
• thinnest
• actin protein filaments
• motility, cell division, shape
• Intermediate filaments
• middle diameter
• keratin
• shape, nucleus anchorage

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Centrosomes/centrioles

• Centrosome region near nucleus
• Centrioles 9 sets of triplet microtubules in a
  ring used in cell replication only in animal
  cells

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Cilia/flagella

• Locomotive appendages
• Ultrastructure 92
• 9 doublets of microtubules in a ring
  
• 2 single microtubules in center
• connected by radial spokes
• anchored by basal body
• dynein protein

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Review plant vs. animal

• Animal
• Pretty much there are no additional organelles in
  an animal cell compared to a plant cell

• Plant
• Primarily has 3 extra structures
• Plastids/ chloroplasts
• Cell wall
• Central vacuole

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Cell surfaces junctions

• Cell wall
• not in animal cells
• protection, shape, regulation
• Plant cell
• primary cell wall produced first
• middle lamella of pectin (polysaccharide) holds
  cells together
• some plants, a secondary cell wall strong
  durable matrix wood (between plasma membrane and
  primary wall)

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Extracellular matrix (ECM)

• Glycoproteins
• proteins covalently bonded to carbohydrate
• Collagen (50 of protein in human body)
• embedded in proteoglycan (another
  glycoprotein-95 carbohydrate)
• Fibronectins
• bind to receptor proteins in plasma membrane
  called integrins (cell communication?)

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Intracellular junctions

• PLANTS
• Plasmodesmata
• cell wall perforations water and solute passage
  in plants
• ANIMALS
• Tight junctions fusion of neighboring cells
  prevents leakage between cells
• Desmosomes riveted, anchoring junction strong
  sheets of cells
• Gap junctions cytoplasmic channels allows
  passage of materials or current between cells