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“ !” completely different mechanisms. catalysis: the process by which a catalyst changes the rate and mechanism of a chemical reaction -- a catalyst is…

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Presentation on theme: "“ !” completely different mechanisms. catalysis: the process by which a catalyst changes the rate and mechanism of a chemical reaction -- a catalyst is…"— Presentation transcript:

1 “ !” completely different mechanisms. catalysis: the process by which a catalyst changes the rate and mechanism of a chemical reaction -- a catalyst is… NOT consumed during the course of a reaction -- Catalyzed and uncatalyzed reactions have... This is WHY catalyzed and uncatalyzed reactions have different activation energies.

2 Catalytic converters often use Pt as a catalyst to help turn CO into CO 2, N x O x into N 2 and O 2, and unburned hydrocarbons into CO 2 and H 2 O. Heterogeneous catalysts exist in a different phase than the reacting molecules. -- usually solid catalysts in gaseous mixtures or liquid solutions Research on catalysts is one of the most important areas of modern science. Homogeneous catalysts are present in the same phase as the reacting molecules.

3 The first step in heterogeneous catalysis is _________ of the reactant molecules onto the metal surface – specifically, onto the _________, which are the locations at which reactants attach to the metal catalyst. adsorption active sites then, the products detach from the catalyst R bonds are broken or weakened, allowing P to form w /a lower E a enzymes: biological catalysts -- large protein molecules -- usually very specific -- names end in... “____” -- substrates: substances (i.e., reactants) that react at the active sites of enzymes (10 4 – 10 6 amu)  for only one reaction -ase

4 -- The lock-and-key model explains how an enzyme affects a substrate molecule and changes it into a new substance. Lock-and-Key Model substrate (i.e., reactant) enzyme active site active site is ready for more substrate products enzyme-substrate complex

5 turnover number:~10 3 – 10 7 per sec. Enzyme inhibitors bind to the active site or alter the unique shape of an enzyme molecule, destroying the enzyme’s activity. e.g., poisons, Pb, Hg, others


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