Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesLesson OverviewLesson Overview2...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesTHINK ABOUT ITLiving things are...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsWhat happens ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsWhat happens ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsA chemical re...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsAn important ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsAs it enters ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsIn the lungs,...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy in ReactionsHow do energ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy in ReactionsHow do energ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesEnergy is release...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesAn example of an ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesThe reverse react...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy SourcesEvery organism mu...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesActivation EnergyChemical react...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesActivation EnergyThe peak of ea...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesWhat role do enzymes pla...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesWhat role do enzymes pla...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesSome chemical reactions ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsEnzymes are p...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsFor example, ...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsEnzymes are v...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexFor...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexThe...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexThe...
Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesRegulation of Enzyme ActivityTe...
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CVA Biology I - B10vrv1024

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CVA Biology I - B10vrv1024

  1. 1. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesLesson OverviewLesson Overview2.4 Chemical Reactions2.4 Chemical Reactionsand Enzymesand Enzymes
  2. 2. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesTHINK ABOUT ITLiving things are made up of chemical compounds, but chemistry isn’tjust what life is made of—chemistry is also what life does.Everything that happens in an organism—its growth, its interaction withthe environment, its reproduction, and even its movement—is based onchemical reactions.
  3. 3. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsWhat happens to chemical bonds during chemical reactions?
  4. 4. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsWhat happens to chemical bonds during chemical reactions?Chemical reactions involve changes in the chemical bonds that join atomsin compounds.
  5. 5. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsA chemical reaction is a process that changes, or transforms, one set ofchemicals into another by changing the chemical bonds that join atoms incompounds.Mass and energy are conserved during chemical transformations, includingchemical reactions that occur in living organisms.The elements or compounds that enter into a chemical reaction are knownas reactants.The elements or compounds produced by a chemical reaction are knownas products.
  6. 6. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsAn important chemical reaction in your bloodstream enables carbon dioxideto be removed from the body.
  7. 7. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsAs it enters the blood, carbon dioxide (CO2) reacts with water to producecarbonic acid (H2CO3), which is highly soluble.This chemical reaction enables the blood to carry carbon dioxide to thelungs.
  8. 8. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesChemical ReactionsIn the lungs, the reaction is reversed and produces carbon dioxide gas,which you exhale.
  9. 9. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy in ReactionsHow do energy changes affect whether a chemical reaction will occur?
  10. 10. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy in ReactionsHow do energy changes affect whether a chemical reaction will occur?Chemical reactions that release energy often occur on their own, orspontaneously. Chemical reactions that absorb energy will not occurwithout a source of energy.
  11. 11. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesEnergy is released or absorbed whenever chemical bonds are formed orbroken during chemical reactions.Energy changes are one of the most important factors in determiningwhether a chemical reaction will occur.Chemical reactions that release energy often occur on their own, orspontaneously.Chemical reactions that absorb energy will not occur without a source ofenergy.
  12. 12. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesAn example of an energy-releasing reaction is the burning of hydrogengas, in which hydrogen reacts with oxygen to produce water vapor.The energy is released in the form of heat, and sometimes—whenhydrogen gas explodes—light and sound.
  13. 13. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy ChangesThe reverse reaction, in which water is changed into hydrogen andoxygen gas, absorbs so much energy that it generally doesn’t occur byitself.2H2O + energy  2 H2 + O2The only practical way to reverse the reaction is to pass an electricalcurrent through water to decompose water into hydrogen gas andoxygen gas.Thus, in one direction the reaction produces energy, and in the otherdirection the reaction requires energy.
  14. 14. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnergy SourcesEvery organism must have a source of energy to carry out the chemicalreactions it needs to stay alive.Plants get their energy by trapping and storing the energy from sunlightin energy-rich compounds.Animals get their energy when they consume plants or other animals.Humans release the energy needed to grow, breathe, think, and evendream through the chemical reactions that occur when we metabolize,or break down, digested food.
  15. 15. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesActivation EnergyChemical reactions that release energy do not always occurspontaneously.The energy that is needed to get a reaction started is called theactivation energy.
  16. 16. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesActivation EnergyThe peak of each graph represents the energy needed for the reactionto go forward.The difference between the required energy and the energy of thereactants is the activation energy. Activation energy is involved inchemical reactions whether or not the overall reaction releases orabsorbs energy.
  17. 17. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesWhat role do enzymes play in living things and what affects their function?
  18. 18. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesWhat role do enzymes play in living things and what affects their function?Enzymes speed up chemical reactions that take place in cells.Temperature, pH, and regulatory molecules can affect the activity ofenzymes.
  19. 19. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesEnzymesSome chemical reactions are too slow or have activation energies that aretoo high to make them practical for living tissue.These chemical reactions are made possible by catalysts. A catalyst is asubstance that speeds up the rate of a chemical reaction.Catalysts work by lowering a reaction’s activation energy.
  20. 20. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsEnzymes are proteins that act as biological catalysts. They speed upchemical reactions that take place in cells.Enzymes act by lowering the activation energies, which has a dramaticeffect on how quickly reactions are completed.
  21. 21. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsFor example, the reaction in which carbon dioxide combines with waterto produce carbonic acid is so slow that carbon dioxide might build up inthe body faster than the bloodstream could remove it.Your bloodstream contains an enzyme called carbonic anhydrase thatspeeds up the reaction by a factor of 10 million, so that the reactiontakes place immediately and carbon dioxide is removed from the bloodquickly.
  22. 22. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesNature’s CatalystsEnzymes are very specific, generally catalyzing only one chemicalreaction.Part of an enzyme’s name is usually derived from the reaction itcatalyzes.Carbonic anhydrase gets its name because it also catalyzes the reversereaction that removes water from carbonic acid.
  23. 23. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexFor a chemical reaction to take place, the reactants must collide withenough energy so that existing bonds will be broken and new bonds willbe formed.If the reactants do not have enough energy, they will be unchangedafter the collision.Enzymes provide a site where reactants can be brought together toreact. Such a site reduces the energy needed for reaction.
  24. 24. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexThe reactants of enzyme-catalyzed reactions are knownas substrates.For example, the enzymecarbonic anhydrase converts thesubstrates carbon dioxide andwater into carbonic acid (H2CO3).
  25. 25. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesThe Enzyme-Substrate ComplexThe substrates bind to a site on the enzyme called the active site.The active site and the substrates have complementary shapes.The fit is so precise that the active site and substrates are oftencompared to a lock and key.
  26. 26. Lesson OverviewLesson Overview Chemical Reactions and EnzymesChemical Reactions and EnzymesRegulation of Enzyme ActivityTemperature, pH, and regulatory molecules are all factors that canaffect the activity of enzymes.Enzymes produced by human cells generally work best at temperaturesclose to 37°C, the normal temperature of the human body.Enzymes work best at certain pH values. For example, the stomachenzyme pepsin, which begins protein digestion, works best under acidicconditions.The activities of most enzymes are regulated by molecules that carrychemical signals within cells, switching enzymes “on” or “off” as needed.
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