2.4 chemical reactions and enzymes. 2 chemical reactions a process that changes or transforms one...
TRANSCRIPT
2.4 Chemical Reactions and Enzymes
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Chemical Reactions
• A process that changes or transforms one set of chemicals into another
• Mass and energy are conserved• Reactants Products• 2 kinds: energy releasing
(exothermic) and energy absorbing (endothermic)
Exothermic Reactions
• Reaction in which heat is given off (Ex. combustion of fuels)
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Endothermic Reactions
• Reaction in which heat is absorbed (Ex. water is evaporated)
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Activation Energy
• Energy needed to get a reaction going
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Catalyst
• A substance that speeds up the rate of a reaction
• It works by lowering activation energy
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Enzymes
• Proteins that act as biological catalysts
• They speed up chemical reactions that take place in cells
• They are very specific and usually catalyze only one chemical reaction
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Substrates
• The reactants of enzyme-catalyzed reactions
• They bind to sites on the enzyme called active sites Lock and Key
• CO2 + H2O H2CO3
substrate
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http://www.youtube.com/watch?v=CZD5xsOKres
Regulation of Enzyme Activity
• Temperature, pH, and regulatory molecules can affect how well enzymes work
• Pepsin works best under acidic conditions (begins protein digestion)
• Some are regulated by molecules that carry chemical signals within cells that turn enzymes “on” or “off”
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