BIS 104 PQ 6 ans Spring 2010

BIS 104 PQ 6 ans Spring 2010 - transcription factors and...

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BIS 104 PQ 6 ans Spring 2010 6. For each of the items listed below describe i) its composition and location, and ii) its major function(s). The first one is done for you as an example of an appropriate answer to this type of question. A) NUCLEAR PORE COMPLEX (NPC) i) Located in the double nuclear membrane of eukaryotic cells; there are approximately 1,000 per nucleus and they are composed of an octagonal complex of approximately 20 different proteins. ii) The NPC, in conjunction with carrier proteins such as exportins and importins, controls the entry and exit of molecules that pass between the cytosol and the nucleoplasm. B) NUCLEOSOSME i) Repeating units of DNA and histone proteins found in the nucleus; conststitutes the arrangement of chromatin. 146 base pairs of supercoiled DNA wrapped around a complex of eight histone molecules . ii) Main function is packaging of DNA and structural level control of access of genes to
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Unformatted text preview: transcription factors and other regulators of gene expression. C) ENDOPLASMIC RETICULUM (ER) i) A lipid bilayer system of tubules, cisternae and vesicles in the cytoplasm of eukaryotic cells; cis-face component is continuous with outer nuclear membrane. ii) Provides a compartment for the synthesis of lipids and sterols and detoxification of xenobiotics (SER) or synthesis of secretory proteins (RER). Site of preliminary processing of these products: e.g., folding, glyscosylation, sorting into transport vesicles. D) MICROTUBULES (MTs) i) 25 nm diameter dynamic tubules composed of alpha and beta tubulin dimers; in the cytoplasm of eukaryotic cells. ii) Major component of cytoskeleton working in conjunction with motor proteins responsible for cell shape stability, transport of intracellular components, arrangement of organelles, and chromosome movement (as the mitotic spindle)....
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