Questionscytomembranes - Cytoplasmic Membrane Systems The...

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Cytoplasmic Membrane Systems The following questions are a guide to your preparation for Examination II. 1. What are the major organelles in a eukaryotic cell? What do we mean by organelle? What organelles belong to the endomembrane system? How would you describe this system? Be familiar with these terms: exocytosis/endocytosis, anterograde and retrograde trafficking, constitutive and regulative secretion, sorting and targeting of vesicles. Understanding the difference between cytosolic and exoplasmic leaflets of endomembranes. The nucleus, er, golgi apparatus, lysosomes, endosomes, mitochondria and peroxisomes are distinct compartments separated from the cytosol by atleast one selectively permeable membrane. Organelles mean membrane-enclosed compartments of eukaryotic cell. Nucleus, ER, Golgi, lysosomes, endosomes, vesicles are part of endomembrane system. Function of endomembrane system: protein (and lipid) synthesis, processing, sorting and packaging for specific target sites. It is dynamic, integrated, ordered membrane bound Anterograde - Moving forward or extending forward. Moving from nucleus to ER to Golgi to plasma membrane Retrograde - From outside of cell towards nucleus Constitutive secretion - In constitutive secretion , proteins are packaged in vesicles in the Golgi apparatus and are secreted immediately via exocytosis, all around the cell. They secrete continuously and unlike the regulated pathway, no external signal is needed to stimulate the process. Cells that secrete constitutively have many Golgi apparatus scattered throughout the cytoplasm. Fibroblasts, osteoblasts and chondrocytes are some of the many cells that use this pathway. Regulated Secretion - In regulated secretion , proteins are packaged as described in the constitutive pathway, but they are only secreted in response to a specific signal, such as neural or hormonal stimulation. Cells that use the regulated secretory pathway are usually apical or polarized. The Golgi apparatus are found in a supranuclear position (between the nucleus and the secretory surface). Example cells that use regulated pathway are: goblet cells (secrete mucus), beta cells of the pancreas (secrete insulin) and odontoblasts (secrete dentin). 2. Be able to describe some of the properties of the nuclear pore. What types of transport take place here? What is being transported? Review the basic steps by which the nuclear protein lamin would be transported from the cytoplasm to the nucleus. .Your answer should include an understanding of: NLS, importin, GTP-RAN. The nuclear envelope in all eucaryotic cells is perforated by nuclear pores that form the gaes through which all molecules enter or leave the nucleus. Traffic occurs in both directions through the pores: newly made proteins destined for the nucleus enter from the cytosol; RNA molecules, which are synthesized in the nucleus, and ribosomal subunits, which are assembled in the nucleus are exported. mRNA molecues that are incompletely spliced are not exported from the nucleus, suggesting that nuclear transport serves a final
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This note was uploaded on 05/22/2008 for the course CELL BIO & 270 taught by Professor Hart during the Spring '08 term at Rutgers.

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Questionscytomembranes - Cytoplasmic Membrane Systems The...

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