cell bio section 2.1 outline

cell bio section 2.1 outline - Chapter 14: Mitochondria and...

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Chapter 14: Mitochondria and Chloroplasts: The Structure of Mitochondria: Remarkably plastic organelles, constantly changing their shape. As they move about in the cytoplasm they are often associated w/microtubules which can determine the unique orientation and distribution of mitochondria in diff types of cells. In some cells they form long moving filaments or chains; in other cells they remain fixed in one position where they provide ATP to a site of unusually high ATP consumption such as b/w adjacent myofibrils in a cardiac muscle cell or wrapped around the flagellum in a sperm. Each mitochondrion is enclosed by two highly specialized membranes which have very different functions. Together they form two separate compartments: the internal matrix and a much narrower intermembrane space . Each contains a unique collection of proteins. Most of these are encoded in the nucleus and imported into the mitochondrion by specialized protein translocases (TOM and TIM) in the outer and inner membranes. The outer membrane contains porin channels, a type of transport protein that forms aqueous channels though the bilayer. The outer membrane thus is permeable to all molecules of 5000 or less Daltons, including small proteins, but the inner membrane is impermeable to them so they stay in the intermembrane space. It alos contains enzymes for mitochondrial lipid synthesis and metabolism. The major working part of the mitochondrion is the matrix and the inner membrane that surrounds it. Its lipid bilayer contains a high proportion of the “double” phospholipid cadiolipin which has four fatty acids rather than two and may help to make the membrane especially impermeable to ions. It also contains a variety of transport proteins that make it selectively permeable to those small molecules that are metabolized or required by the many mitochondrial enzymes concentrated in the matrix. It contains proteins for oxidation reactions of the electron transport chain and ATP synthetase. The matrix contains mtDNA, tRNA, the translation system, enzymes for gene expression and matrix enzymes include those that metabolize pyruvate to acetyl CoA and those that oxidize acetyl CoA in the citric acid cycle . The principle end products of this oxidation are CO2 and NADH which is the main source of electrons fro transport along the respiratory chain (name given to electron transport chain in mitochondria). The inner membrane is highly convoluted, forming a series of infoldings called cristae that greatly increase the surface area. Mitochondria Extract High-energy Electrons from Food (Aerobic Oxidation): Mitochondria use both pyruvate and fatty acids as fuel. Pyruvate comes from glucose and other sugars; fatty acids come from fats. Both fuel molecules are transported across the inner mitochondrial membrane and are then converted to acetyl CoA by enzymes located in the mitochondrial matrix.
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cell bio section 2.1 outline - Chapter 14: Mitochondria and...

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