Details of the Endomembrane System

Endomembrane system Synthesis, storage, export and destruction of molecules and wastes Rough ER ‘studded’ with ribosomes Proteins made here enter into ER to be transported around cell or exported out of cell!!!! Site of phospholipid production Smooth ER Synthesis of lipids, cholesterol Detoxify drugs and wastes Storage of calcium Golgi apparatus Shipping and receiving center for cell Receives products from ER and routes them to appropriate location Lysosomes Hydrolytic enzymes; degrades macromolecules or old organelles Vacuoles Site of waste/nutrient storage Plants - central vacuole Protists - contractile vacuoles and food vacuoles Transport vesicles move proteins, lipids, and other cargo between endomembrane system and plamsa membrane © 2012 Pearson Education, Inc.

Rough ER • ‘studded’ with ribosomes • Proteins made by ER-associated ribosomes would function in a cell membrane, within endomembrane system organelle, in plasma membrane, or outside cell!! Nuclearenvelope Ribosomes Smooth ER Rough ER • Smooth ER • Synthesis of lipids, cholesterol • Detoxify drugs and wastes • Storage of calcium

Figure 4.8B Transport vesiclebuds off 4 Secretoryproteininside trans-port vesicle mRNA Ribosome 3 Sugarchain 1 Glycoprotein 2 Polypeptide Rough ER

Golgi apparatus • Shipping and receiving center for cell • Receives products from ER and routes them to appropriate location “Receiving” sideof Golgiapparatus Golgi apparatus Golgi apparatus Transportvesiclefrom ER 1 Transportvesicle fromthe Golgi 2 3 4 “Shipping” side of Golgiapparatus 4

Figure 4.12 Nucleus Nuclearmembrane Rough ER Transportvesicle fromGolgi to plasmamembrane SmoothER Transportvesicle from ERto Golgi Proteins made at RER can be routed to plasma membrane or outside cell or to lysosomes Lysosome Vacuole Plasmamembrane Golgiapparatus

Lysosomes are digestive compartments A lysosome contains digestive enzymes (produced by ER and transferred to lysosomes via Golgi and transport vesicles) Lysosomes help digest food particles engulfed by a cell. Lysosomes also help remove or recycle damaged parts of a cell. Digestiveenzymes Lysosome Digestion Food vacuole Plasma membrane Animation: Lysosome Formation © 2012 Pearson Education, Inc.

Figure 4.10A_s1 Digestiveenzymes Lysosome Plasma membrane

Figure 4.10A_s2 Digestiveenzymes Lysosome Food vacuole Plasma membrane

Figure 4.10A_s3 Digestiveenzymes Lysosome Food vacuole Plasma membrane

Figure 4.10A_s4 Digestiveenzymes Lysosome Digestion Food vacuole Plasma membrane

Figure 4.10B_s1 Lysosome Vesicle containingdamaged mitochondrion

Figure 4.10B_s2 Lysosome Vesicle containingdamaged mitochondrion

Figure 4.10B_s3 Lysosome Digestion Vesicle containingdamaged mitochondrion

Endosymbiosis theory • Mitochondria & chloroplasts were once free living bacteria • engulfed by ancestral eukaryote • Endosymbiont • cell that lives within another cell (host) • as a partnership • evolutionary advantage for both • one supplies energy • the other supplies raw materials & protection Lynn Margulis U of M, Amherst

Endosymbiosis theory Evolution of eukaryotes

Evidence/Support • Mitochondria and Chloroplasts share several characteristics typically associated with prokaryotes: • Both have own DNA that is circular (eukaryotic DNA is always linear) • Some of these genes are more similar to bacterial genes • Both have own ribosomes and protein synthesis machinery • Both can split into new mitochondria or chloroplasts in a manner similar to bacterial reproduction • Both mito and chloroplasts exhibit a double membrane, consistent with engulfment by ancestral eukaryote.

Figure 4.13 Mitochondrion Outermembrane Intermembranespace Innermembrane Cristae Matrix

Figure 4.14 Chloroplast Inner andoutermembranes Stroma Granum Thylakoid

Details of the Endomembrane System