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Why organelles?

Cell: Endomembrane System Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes, Vacuoles, Vesicles. Golgi. mitochondria. chloroplast. ER. Why organelles?. Special structures with special functions Containers with different local environments (pH, ionic conditions, etc)

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Why organelles?

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  1. Cell: Endomembrane System Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes, Vacuoles, Vesicles

  2. Golgi mitochondria chloroplast ER Why organelles? • Special structures with special functions • Containers with different local environments (pH, ionic conditions, etc) • Ex: lysosome & its digestive enzymes • Sites for chemical reactions • Ex: chloroplasts & mitochondria

  3. Endoplasmic Reticulum • Function • Many building functions (like membranes) • Structure • Extends from nuclear membrane throughout cell • rough ER = bound ribosomes • smooth ER = no ribosomes

  4. Smooth ER function • Metabolic processing factory • Synthesis (build) & hydrolysis (break) • enzymes … • build lipids, oils, phospholipids, steroids • In liver  breakdown of glycogen into glucose • In liver  detoxify drugs & poison

  5. Rough ER function • Build proteins for export out of cell • protein secreting cells • packaged into transport vesicles for export

  6. Golgi Apparatus • Function • Finishes, sorts, ships cell products • extensive in cells specialized for secretion

  7. Golgi Apparatus • Structure • flattened membrane sacs = cisternae • 2 sides = 2 functions • cis = receives material by fusing with vesicles = “receiving” • trans buds off vesicles that travel to other sites = “shipping” (transport) cis trans

  8. Golgi processing • While moving from cis to trans, products from ER are modified into final form • tags, sorts, & packages materials into transport vesicles • Golgi = “UPS headquarters” • Transport vesicles = “UPS trucks”

  9. Lysosomes  cell digestion and recycling • Structure • sacs of enzymes that hydrolyze/digest macromolecules • enzymes made by rough ER only in animal cells

  10. Cell digestion • Lysosomes fuse with food vacuoles • Polymers digested into monomers

  11. 1960 | Lysosomes • little “stomach” • lyso– = breaking things apart • –some = body • digests macromolecules • “clean up crew” • cleans up broken down organelles Nobel Prize1974 Where old organellesgo to die! only in animal cells

  12. Lysosome enzymes • work best at pH 5 • organelle creates custom pH • how? • proteins in lysosomal membrane pump in H+ ions from the cytosol • adaptation: • digestive enzymes from lysosomes won’t work if they leak into cytosol = don’t want to digest yourself!

  13. But sometimes cells need to die… • Lysosomes can kill cells when they need to die  for proper development • apoptosis • “self-destruct” • lysosomes break open & kill cell • ex: tadpole tail gets re-absorbed when it turns into a frog • ex: loss of webbing between fingers during fetal development

  14. syndactyly 15 weeks Fetal development 6 weeks

  15. Peroxisomes • Other digestive enzyme sacs • in both animals & plants • breakdown fatty acids to sugars • Why? Sugars are easier energy source • detoxify cell  alcohol/poisons • produce peroxide (H2O2) • must breakdown H2O2 H2O + O (bubbles)

  16. Vacuoles & Vesicles • Vesicles store, transport, or digest cellular products and waste. • Vacuoles contain water • Food vacuoles • phagocytosis, fuse with lysosomes • Contractile vacuoles • pump excess H2O out of cell in protists • Central vacuole in plants • Stockpile byproducts

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