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Why organelles?

Explore the functions and structures of organelles like Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes, Vacuoles, and Vesicles. Discover the roles they play in cellular processes such as metabolism, secretion, digestion, and detoxification.

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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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