The Endomembrane System

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The Endomembrane System

• Raychel Martin
• Courtney Hitt

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Endoplasmic Reticulum

• Network of membranes containing ribosomes
• Commonly referred to as ER

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Smooth ER

• Has enzymes important for the synthesis of lipids
• Oils
• Phospholipids
• Steroids
• Enzymes also used to detoxify drugs and poisons
• Stores calcium ions

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Rough ER

• Makes secretory proteins
• Membrane factory for cell
• Grows in place by adding membrane proteins and
  phospholipids to its own membane
• Turns into transport vessicle

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Golgi Apparatus

• Works as the main manufacturing, shipping, and
  storing center of the cell
• Removes sugar monomers and substitutes others
• Producing carbohydrates

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Golgi Apparatus

• Manufactures certain macromolecules
• Secretes polysaccharides from trans side fusing
  with plasma membrane

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Trans Side

• Sorts products and targets them to different
  parts of cells
• Is where the vesicles bud

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Cis Side

• Receives the vesicles that have been sorted by
  trans

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Cisternal Maturation Model

• Vesicles move from ER to golgi
• Vesicles coalesce to form new cis golgi cisternae
• Golgi cisternae move from a cis to trans
  direction

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Cisternal Maturation Model

• Vesicles form and leave golgi carrying specific
  proteins to other locations or to plasma membrane
  for secretion
• Vesicles transport to specific proteins backwards
  to newer golgi cisternae
• Vesicles transport certain proteins back to ER

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Lysosomes

• Membranous sac of hydrolytic enzymes
• Animal cell uses them to digest macromolecules
• Hydrolytic enzymes and lysosomal membrane are
  made by rough ER and then transferred to Golgi
  for further processing

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Intracellular Digestion

• Lysosomes perform many forms of intracellular
  digestion
• Phagocytosis- food vacuole fuses with lysosome,
  whose enzymes digest food
• Autophagy- lysosomes use hydrolytic enzymes to
  recycle cells own organic material

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Vacuoles

• Vacuoles carry out hydrolysis
• Food Vacuoles
• Formed by phagocytosis
• Digest food
• Contractile Vacuoles
• Pump excess water out of the cell

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Vacuoles

• Central Vacuoles
• Enclosed by membrane called tonoplast
• Developed by coalescence of smaller vacuoles
• Tonoplast is selective in transporting solutes