Golgi apparatus

• The Golgi apparatus is a stack of flattened membrane band compartments (Cisternal) with the ER facing the site where vesicles depart for the cell surface or other compartments.
• The Golgi apparatus functions to sort, modify, and dispatch proteins destined for secretion and for various organelles/resicles within the cell.
• The Golgi apparatus is a major site of glycoprotein and proteoglycan synthesis.
• The Golgi apparatus tends to be prominent in secretory cells.
• The Golgi apparatus is prominent in intestinal goblet cells.
• Almost all proteins in the ER are glycosylated, acting as a folding tag transferase.
• During the initial phases of folding, three to four ER membrane terminal glucose molecules are removed.
• Calnexin is a chaperone that recognizes the single grozose of a completely folded protein and prevents their export to Golgi.
• Calnexin helps to fold a protein.
• The final glucose is removed, then a misfolded protein is chaperoned back to the ER, and protein translocators are sent to the cytoplasm for degradation.
• Lysosomes are membrane-bound compartments and are the major site of intracellular digestion, containing around 40 types of hydrolytic enzymes.
• All of the enzymes in lysosomes are acid hydrolases and are maintained at about pH5 by a H+ pump in the lysosomal membrane.
• Lysosomes contain phospholipases and phosphatases.
• Lysosomes contain lipases and the enzymes needed to digest just about anything.
• Lysosomes protect, nucleases, carbohydrates, and glycosidases.
• Degrade components of the cell Membrane.
• Lysosomes are not specific to any one type of substrate.
• Recycle the products such as AAs & nucleic acids.
• Lysosomes can remove any type of substrate.
• The H+ pump in the lysosomal membrane uses ATP.
• Lysosomes maintain acidic environments around 5.
• Degrade proteins and other substances from outside the cell that are taken up by endocytosis.
• Lysosomes protect themselves from their own digestive enzymes in two ways: the lysosomal membrane keeps the enzyme out of cytosol, and acid hydrolases don't Work at cellular pH 7.
• Bud non-cargos are packaged at a much lower rate.
• Secretary proteins aggregate and then leave the trans Golgi network as loosely bound immature secretary resicles in acidic conditions of Golgi.
• For soluble proteins, involves interactions with transmembrane receptors.
• Retrograde Golgi transport transports vesicles back to the Golgi networks.
• Correctly folded proteins are exported to Golgi and bind to cargo.
• Golgi networks are targeted to the plasma membrane.
• Exocytosis is a type of vesicular transport.
• Fully folded proteins are targeted to ER exit sites.
• Constitutive Secretory pathway involves the secretion of components of the extracellular Matrix and the delivery of new plasma membrane proteins & lipids to cell surface in the Golgi.
• Lysosomes are involved in causing destruction across the cell, degrading things for them to be recycled.
• Proteins need "exit" signals for efficient export.
• Secretion is transported by this route.
• Most exit signals are not known but ERGIC 53 receptor proteins binds to mannose on Factors 2.
• The concentration of Secretary proteins increases as the vesicles mature due to retrieval of membrane back to Golgi and increased acidity in maturing lysosomes, causing tighter aggregation.
• The Coat protein COP11 interacts with the cytosolic tail of the receptor causing a vesicle to bud off.
• Vesicles return to the plasma membrane after recycling or transcytosis.
• Carbohydrates are recycled back to the Golgi to be reused.