Cell Bio notes - I 1. The compartmentalization of cells All...

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The compartmentalization of cells 1. All eucaryotic cells have the same basic set of membrane-enclosed compartments – function of each compartment; their contribution to the total cell volume; relative amounts of membrane contributed by each compartment. Cytosol - site of protein synthesis and degradation; performs most of the cell’s intermediary metabolism (degrade small molecules and synthesize others to provide building blocks for macromolecules; constitutes 54% of cell volume Mitochondria - generate most of the ATP that cells use to drive reactions requiring an input of free energy; 22% of cell volume Rough ER cisternae - has ribosomes bound to cytosolic surfaces (synthesize both soluble and integral membrane potriens) Smooth ER cisternae plus Golgi cisternae - smooth ER lacks ribosomes; golgi cisternae is part of the golgi apparatus which receives lipids and proteins from the ER and dispatches them to various destinations **The ER in general- proteins are transported into the ER as they are synthesized; ER also produces most of the lipid for the rest of the cell and functions as a storehouse for Ca 2+ ions Nucleus - contains the genome, principal site of DNA and RNA synthesis, constitutes 6% of the cell volume Peroxisomes - small vesicular compartments that contain enzymes used in various oxidation reactions; 1% of cell volume Lysosomes - contain digestive enzymes that degrade defunct intracellular organelles; 1% of cell volume Endosomes - series of organelles that endocytosed material must first pass through on the way to lysosomes; 1% of cell volume The plasma membrane is only a minor membrane in most eucaryotic cells; in most cells the ER membrane and the mitochondrial inner membrane are the most abundant; what are the functions performed by these membranes? 2. Toplogical relationships between different membrane-enclosed compartments can be interpreted from their evolutionary origins. The intracellular compartments in eucaryotic cells can be grouped into four distinct families based on their evolutionary origins: (i) the nucleus and the cytosol – communicate with each other through nuclear pore complexes (ii) ER, Golgi apparatus, endosomes, lysosomes, transport vesicles, and possibly peroxisomes (iii) mitochondria (iv) plastids (in plants only) The evolution of internal membranes occurred due to the specialization of membrane function. The invagination and pinching off of specialized intracellular membrane structures from the plasma membrane creates organelles with an interior that is topologically equivalent to the exterior of the cell. 3. Proteins can move between compartments in different ways (i) Gated transport - proteins move from cytosol and nucleus through nuclear pore complexes which function as selective gates that actively transport specific macromolecules and allow free diffusion of smaller molecules (ii) Transmembrane transport - transmembrane protein translocators directly transport specific
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This note was uploaded on 04/12/2008 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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Cell Bio notes - I 1. The compartmentalization of cells All...

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