2.4: Chemical Reactions & Enzymes

1. 2.4: Chemical Reactions & Enzymes chemical reaction: process that changes one set of chemicals into another by changing the chemical bonds that join the atoms elements (or compounds) that enter into a chemical reaction are known as reactants & those produced by a chemical reaction are known as products reactantsproducts

2. energy is releasedor absorbedduring chemical reactions chemical reactions that release energyusually occur on their own chemical reactions that absorb energywill notoccur withouta source of energy

3. every organism must have a source of energyto carryoutthe chemical reactions it needs to stay alive plantsget their energy by trapping and storing the energy from sunlightin energy-rich compounds animalsget their energy when they eat plants or other animals

4. energy that is needed to get a reaction started is called the activation energy activation energy is involvedin chemical reactions whetheror not the overall reaction releasesor absorbsenergy

5. some chemical reactions are too slow or have activation energiesthat are too highto make them practical for living organisms these chemical reactions are made possible by catalysts catalyst: substance that speeds up the rate of a chemical reaction work by loweringa reaction’s activation energy

6. enzymes:globular proteins that act as biological catalysts thousandsof different enzymes existin the body & can be reused enzymes are very specific, catalyzing only one chemical reaction

7. enzymes weakenthe bondswhich lowersthe amountof activation energy needed for the reaction 7

8. reactantsof enzyme-catalyzed reactions are known as substrates Enzyme Substrate Joins 8

9. substratesbind to a site onthe enzyme called the active site Enzyme Active Site Substrate 9

10. active site & substrates have complementary shapeswhich explains whythey are specificto a particular reaction Enzyme

11. temperature, pH, andregulatory moleculesare all factors that can affect enzyme activity best close to normal body temperature & with a pHbetween 6 – 8 ~ extremestend to unfoldthe enzyme most enzymes are regulatedby moleculesthat carry chemical signals(hormones!) within cells, switchingenzymes “on” or “off” as needed

12. Enzyme Animation: http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html