Energy160-page10

Energy160-page10 - mitochondria. Such complexes provide...

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Energy Flow in Cells - 10 When a substrate binds to the enzyme, it "fits" into the active site, temporarily distorting the reacting molecules; this is called the induced fit. This distorted stage of the substrate is called the transition state and its bonds are more easily broken (lowered activation energy), promoting the reaction. Once the reaction occurs, the active site is altered, releasing the product. The enzyme is unaffected by the reaction. Enzymes are highly specific. Each chemical reaction that occurs in cells has its own enzyme. Enzyme shape determines its function. The kinds of enzymes in cells determine what chemical reactions take place and what metabolic activities will occur within that cell. Although many enzymes are located free within the cytoplasm of the cell, others are found within complexes, typically associated with membranes of specific organelles, such as the enzymes needed for cell respiration found in the
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Unformatted text preview: mitochondria. Such complexes provide greater efficiency and control in metabolic pathways. Some enzymes can only work when they have associate molecules, called coenzymes (non-protein organic molecules) or cofactors (mineral ions) present. Many of our vitamins function as coenzymes in electron transport pathways picking up the electrons removed from the substrate and carrying them (and their associated H + ) to the next reaction in the pathway in a series of oxidation-reduction reactions. Some of our minerals, notably zinc, copper and iron, function as cofactors. Cofactors in the active site attract electrons from the substrate promoting the reaction. Some metals may interfere with enzyme function. Mercury, for example, inhibits the function of many enzymes, partly by blocking the attachment of the needed cofactor....
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