Endomembrane System

Endomembrane System regulates protein traffic and performs metabolic functions The endomembrane system consists of : 2 1 I Nuclear envelope These components are either continuous or connected via transfer by vesicles 4 3I Endoplasmic reticulum Golgi apparatus (ER) 1 Lysosomes Golgi complex (GC) accounts for more than half of the total Vacuoles Plasma membrane (PM) Large vesicles derived from Shipping and Receiving Center membrane in many eukaryotic cells 6 5 the ER and Golgi apparatus consists of flattened membranous sacs called cisternae The ER membrane is continuous with the nuclear envelope – Modifies products of the ER (mostly sugars) Rough ER – Manufactures certain macromolecules (polysaccharides) – Sorts and packages materials into transport vesicles Two types of ER Smooth ER Cis - golgi Finally the vesicle fuse to a Lysosome or fuse with Rough ER BREAMS . ↳ has ribosomes studded on its surface Smooth ER cis face ( receive ) lacks ribosomes Trans face ( ship ) . 0sgfSn#e – Has bound ribosomes, which secrete glycoproteins – Distributes transport vesicles – Is a protein and membrane factory for the cell the plasma membrane and release its content Lysosomes Trans - golgi - Synthesizes lipids ⑧ – Detoxifies drugs and poisons – Stores calcium ions The vesicle reaches at – Metabolizes carbohydrates Glycoproteins: (proteins covalently bonded to carbohydrates) as Plasma membrane ( Cis Golgi ) and get Rough ER Vesicles : (secretory proteins surrounded by membranes) then ( Trans Golgi ) ship it in a transport vesicle Smooth ER Smooth ER Cis - golgi • ER synthesis a biological macromolecule bulk transportation Rough ER sorted and modified and ( protein, polysaccharide ) And leaves in a transport vesicle Plasma membrane Lysosomes man Trans - golgi Plasma membrane Last lecture Small molecules and water enter or leave the cell through the lipid bilayer or via Transport proteins Large molecules such as polysaccharides and proteins cross the membrane in bulk inside vesicles Endocytosis One main pathway ( Outside - inside ) PM • Endosomes . Lysosomes Exocytosis Two main pathways macromolecules are taken into the cell in vesicles The membrane forms a pocket that deepensand pinches off forming a vesicle around the material for transport Pinocytosis Receptor-mediated endocytosis (cellular drinking) ER ER Phagocytosis (cellular eating) • • 2 (inside-outside) GC GC • • PM Lysosomes ) 3 Mediated by transport vesicles I molecules are taken up when extracellular In receptor-mediated endocytosis, binding of fluid is “gulped” into tiny vesicles ligands to receptors triggers vesicle formation Pinocytosis is nonspecific for the substances it transport A ligand is any molecule that binds specifically any and all solutes are taken into the cell to a receptor site of another molecule Parts of the plasma membrane that form Coated vesicles with specific solutes ( purple ) Bound to receptor ( red ) • - vesicles are lined on the inner side with coat proteins, forming coated vesicles a cell engulfs a particle by extending pseudopodia around it and packing it in a membranous sac called a food vacuole The vacuole fuses with a lysosome to digest the particle White blood cell such as WBCs engulfing bacteria Amoeba engulfs green algalcell transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell 2 3 example : cells in the pancreas secrete insulin by exocytosis 5