北京大学：《细胞生物学 Cell Science》课程教学资源（PPT课件讲稿）Cytoplasmic membrane systems：

Cell science (81-2-3) 蔡国平

细胞科学 Cell Science （8.1-2-3） 蔡国平

s8 Cytoplasmic membrane systems: Cytoplasmic Membrane System or Cytomembranes Internal Membrane or Endomembrane System (EMS) includes: nuclear envelopes, endoplasmic reticulum (ER), Golgi complex(GC), lysosomes and a variety of vesicles or vacuoles. Although each of these membranous organelles has its own distinct structure and function, taken togather they forman endomem brane system in which the individual components function as part of a coordinated unit Several other membranous organelles in cytoplasm--mitochandria, peroxisomes, an d chloroplasts-are not part of this interconnected system

§ 8 Cytoplasmic membrane systems: Cytoplasmic Membrane System or Cytomembranes Internal Membrane or Endomembrane System (EMS) includes: nuclear envelopes, endoplasmic reticulum (ER), Golgi complex (GC), lysosomes and a variety of vesicles or vacuoles. Although each of these membranous organelles has its own distinct structure and function, taken togather they form an endomembrane system in which the individual components function as part of a coordinated unit. Several other membranous organelles in cytoplasm—mitochandria, peroxisomes, and chloroplasts—are not part of this interconnected system

gure 141 Electron mIcrograph of part a liver cell seen in cross-section endosome embrane- bounded compartments peroxisome Golgi apparatus endoplasmic hembrane-bound nucleus membrane 15g igure 14-2 The major membrane- bounded organelles of an animal cell. This cell from the lining of the intestine contains the basic set of organelles found in most animal cells. The nucleus, endo The Relative Volumes Occupied by the Major plasmic reticulum(ER), Golgi apparatus, Membrane-bounded Organelles in a lysosomes, endosomes, mitochondria, and Liver Cell (Hepatocyte) peroxisomes are distinct compartments Intracellular Percent of Approximate eparated from the cytosol (gray) by at Compartment Total Cell Volume Number per Cell least one selectively permeable mem Cytosol brane. Ribosomes are also shown, even Mitochondria though they are not enclosed by a mem Endoplasmic reticulum 522 brane and are too small to be seen in a Nucleus ght microscope and therefore do not fit Golgi apparatus the original definition of an organelle Peroxisomes 631 400 Some ribosomes are found free in the LysoSome cytosol, while others are bound to the Endosomes cytosolic surface of the ER

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Plasma membrane Extracellular medium Endocytic vesicle Nuclear envelope Transport endosome Late endosome vesicles neoplasm Ribosomes reticulum endoplasmic reticulum Peroxison Cytosol Figure 12-1 Cellular Structures Discussed in This Chapter. The interior of the endoplasmic reticulum, in turn, is linked to the This chapter focuses on the endoplasmic reticulum, the Golgi complex, interiors of the Golgi complex, endosomes, and lysosomes by transport endosomes, lysosomes, and peroxisomes. Also relevant to the vesicles that shuttle from organelle to organelle. Together, the discussion are the nuclear envelope and plasma membrane. The urrounding membranes and internal spaces of these structures define perinuclear space between the two membranes of the nuclear the endomembrane system of the eukaryotic cell; the remaining envelope is continuous with the interior of the endoplasmic reticulum. portion of the cytoplasm is called the cytosol

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Gola complex ER Secretory ' x d vesicle 3

8. 1. The dynamic nature of the endomembrane system a dynamic, integrated network in which materials are shuttled back and forth from one part(the membrane of donor organelles) of the cell to another (the membrane of acceptor compartment) by transport vesicles. Repeated cycle of budding and fusion of transport vesicles move materials along pathways and tracks formed by cytoskeleton through the cell

8.1. The dynamic nature of the endomembrane system A dynamic, integrated network in which materials are shuttled back and forth from one part (the membrane of donor organelles) of the cell to another (the membrane of acceptor compartment) by transport vesicles. Repeated cycle of budding and fusion of transport vesicles move materials along pathways and tracks formed by cytoskeleton through the cell

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Several distinct pathways for transport of materials through the endomembrane system (1) Biosynthetic pathway: along this pathway materials are synthesized in ER or GC, modified and incorporated into the ER, GC, lysosomes and a variety of vacuoles during passage and transport from er to the gC and to various destination organelles(plasma membrane, and organelles of EMS etc. (2)Secretory pathway: materials synthesized in ER or GC are destined to be discharged to extracellular space fro om the cell (secretion)-by two types Constitutive secretion to form both ECM and the plasma membrane itself in a continual batch manner for most cells Regulated secretion: first stored in secretory granules, in the peripheral area and then discharged hormones, digestive enzymes and neurotransmitters etc. only in response to an appropriate stimulus

Several distinct pathways for transport of materials through the endomembrane system: (1) Biosynthetic pathway: along this pathway, materials are synthesized in ER or GC, modified and incorporated into the ER, GC, lysosomes and a variety of vacuoles during passage and transport from ER to the GC, and to various destination organelles (plasma membrane, and organelles of EMS etc.). (2) Secretory pathway:materials synthesized in ER or GC are destined to be discharged to extracellular space from the cell (Secretion)–by two types: Constitutive secretion to form both ECM and the plasma membrane itself in a continual batch manner for most cells. Regulated secretion: first stored in secretory granules, in the peripheral area and then discharged hormones, digestive enzymes and neurotransmitters etc. only in response to an appropriate stimulus

Lipids, carbohydrates and the most proteins synthesized in the cell are all transported through the cell along the above two pathways (3)Endocytic pathway: by this pathway, materials move from the surface of the cell to compartments such as endosomes and lysosomes etc. within the cytoplasm Like to trucks transport, it require defined traffic patterns (pathways and vehicles) and is specifically targeted using specific addresses or sorting signals

* Lipids, carbohydrates and the most proteins synthesized in the cell are all transported through the cell along the above two pathways. (3) Endocytic pathway: by this pathway, materials move from the surface of the cell to compartments, such as endosomes and lysosomes etc. within the cytoplasm. Like to trucks transport, it require defined traffic patterns (pathways and vehicles) and is specifically targeted using specific addresses or sorting signals

Nuclear Golgi comple (5 Secretory vesicles envelope GN TGN aNterograde transport 5a constitutive Exocytosis secretion Secretory (6)Late Nucleus ② Lysosome ( ○ endosome Plasma membrane ① Rough ER 39的-叫m Figure 12-8 Vesicular Traffic Through the Endomembrane System vesicles bud off to form secretory vesicles or endosomes Vesicles carry lipids and proteins along several routes from the ER through depending on their protein content. Secretory vesicles move to the plasma the Golgi complex to various destinations, including secretory vesicles membrane where they release their contents by exocytosis, either 52 endosomes, and lysosomes. O Proteins are synthesized by ribosomes constitutively or e9 in response to an appropriate signal. O Proteins and attached to the cytosolic surface of the rough ER. Initial glycosylation steps other material are taken into the cell by endocytosis, forming endocytic occur within the ER lumen. @2 Transition vesicles carry newly synthesized vesicles that fuse with (a endosomes. @ existing lysosomes, or (e the and glycosylated proteins to the CGN. (3 Proteins move through the cisternae of the Golgi stack via shuttle vesicles. Glycoproteins are further TGN, depending on the nature of the enclosed material. (8)Cellular components not destined for digestion following endocytosis are recycled processed in various compartments. Retrograde traffic retums to the plasma membrane. 9 Material for digestion travels to a late compartment-specific proteins to earlier compartments. At the TGN endosome, which becomes a lysosome