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Download Enzymes: Molecules That Speed Up Reactions - juan-roldan
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Enzymes: Molecules That Speed Up Reactions What are Enzymes • • • Enzymes are proteins that speed up the rate of all reactions. Also know as Biological Catalysts. Enzymes lower the Activation Energy, which is the energy required to break down existing bonds between atoms Enzymes speed up two types of reactions: 1. Exergonic Reactions 2. Endergonic Reactions Enzyme 3D Molecular Model Active site (a) (b) How Enzymes Work • Every cell carries out many thousands of metabolic reactions per second. Each reaction starts with Reactants (molecules undergoing the reaction) and ends up with a Product or Products. • Reactants (also known as Substrates) bind to the Active Site of the enzyme and form an Enzyme-Substrate Complex. At this time reactants undergo chemical changes that involve the “making or breaking” bonds • Then reactants are transformed into products Enzymes at Work Enzymes at Work Enzyme Reactions • Enzymes speed up two types of reactions: 1. Exergonic Reactions: Bond Breaking 2. Endergonic Reactions: Bond Making Exergonic Reactions • Reactions that break bonds (bond breaking) • Release energy stored within the bonds Energy is Released Endergonic Reactions • Reactions that build bonds (bond making) • Require the input of energy to make bonds Energy is Required Factors Affecting Enzymes 1. Enzyme Concentration • The total amount of enzyme present at the time of the reaction 2. Temperature • Enzymes work best at an optimum temperature • Most enzymes in humans work best at 37ºC 3. pH • Most enzymes are effective only in a narrow pH range • Enzymes work best at on optimum pH Factors Affecting Enzymes 4. Cofactors: Substances that bind to enzymes and help enzymes work best • Organic Cofactors: Vitamins and other compounds made from vitamins. Organic cofactors are alos known as coenzymes Ex: Vitamins A, B, D, E, K, etc. • Inorganic Cofactors: Metal atoms such as Copper, Zink, Magnesium, Iron, etc. 5. Inhibitors: Substances that interfere with enzymes, reducing or even destroying the enzyme activity Ex: Cyanide, poisons, pesticides, painkillers, etc Rate of reaction (a) Figure 6-12 Page 132 Most human enzymes Enzymes of heal-tolerant bacteria (b) Rate of reaction Temperature (˚C) Trypsin Pepsin pH Rate of reaction Rate of reaction Enzyme concentration (a) Substrate concentration (b)
