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Energy and chem reactions in cells

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Energy and chem reactions in cells

  1. 1. Energy and Chemical Reactions in Cells<br />
  2. 2. Energy and Chemical Reactions<br />Energy for Life Processes<br />Energy is the ability to move or change matter.<br />Energy exists in many forms; including light, heat, chemical energy, mechanical energy, and electrical energy.<br />
  3. 3. Energy<br />Energy can be converted from one form to another.<br />In any transfer of energy or conversion of energy from one form to another, the total amount of energy does not change. <br />The total amount of usable energy however always decreases.<br />
  4. 4. Energy<br />Heat causes a cooking egg to change color and solidify.<br />The energy transferred to the egg by heat rearranges the atoms and molecules in the egg.<br />
  5. 5. Energy<br />Energy can be stored or released by chemical reactions. <br />A chemical reactionis a process during which chemical bonds between atoms are broken and new ones are formed, producing one or more different substances.<br />
  6. 6. Energy<br />At any moment thousands of chemical reactions are occurring in every cell in your body.<br />The starting materials for chemical reactions are called reactants.<br />The newly formed materials are called products.<br />Putting a Mentos mint into a<br />Diet Coke will create a dramatic<br />chemical reaction<br />
  7. 7. Energy<br />Chemical reactions are summarized by chemical equations, which are written in the following format:<br />Reactants  Products<br /> The arrow reads as “changes to” or “forms”.<br />For example, dissolving sodium chloride in water causes the following reaction:<br />NaCl  Na+ + Cl-<br />
  8. 8. Energy in Chemical Bonds<br />In chemical reactions, energy is absorbed or released when chemical bonds are broken and new ones formed.<br />Some chemical reactions release energy while other chemical reactions absorb energy.<br />
  9. 9. Energy in Chemical Bonds<br />Freezing and melting of water are physical, not chemical, changes.<br />Freezing and melting are good examples of how energy is absorbed and released.<br />
  10. 10. Energy in Chemical Bonds<br />When water freezes, the process that leads to the formation of ice crystals causes heat energy to be released.<br />When you place water in the freezer to make ice cubes, heat is released from the water as the water freezes. <br />
  11. 11. Energy in Chemical Bonds<br />When you remove ice cubes from the freezer, the ice begins to melt.<br />As ice melts, it absorbs heat from the environment.<br />When you hold a piece of ice, your hand gets cold and heat is transferred from your hand to the ice as the ice begins to melt.<br />
  12. 12. Energy in Chemical Bonds<br />Metabolism is the term used to describe all the chemical reactions that occur within an organism. <br />A chemical reaction causes<br />fireflies to give off bioluminescent <br />light energy<br />
  13. 13. Energy in Chemical Bonds<br />Your cells get most of the energy needed for metabolism from the food you eat.<br />As food is digested, chemical reactions convert the chemical energy in food molecules to forms of energy that can be used by the cells.<br />
  14. 14. Activation Energy<br />The heat from a flame transfers enough energy to ignite the logs in a campfire. <br />The spark from a spark plug causes the gasoline in an automobile engine to ignite. <br />In both cases energy is needed to start a chemical reaction.<br />The energy needed to start a chemical reaction is called activation energy.<br />
  15. 15. Activation Energy<br />Activation energy is a chemical push that gets a chemical reaction in motion.<br />Even in a chemical reaction that releases energy, activation energy must first be applied before the reaction can occur.<br />
  16. 16. Enzymes<br />Like engines, cells consume fuel because they need energy to function.<br /> Just like an engine requires a spark to begin burning gas, biochemical reactions that occur in cells need activation energy to occur.<br />
  17. 17. Enzymes<br />The chemical reactions in cells occur quickly and at relatively low temperatures because of the actions of enzymes.<br />Enzymes are substances that increase the speed of chemical reactions.<br />An enzyme speeds up a chemical<br /> reaction by lowering its energy of <br />activation, the energy that must be<br /> supplied in order for molecules to <br />react with one another.<br />
  18. 18. Enzymes<br />Most enzymes are proteins.<br />Enzymes are catalysts, which are substances that reduce the activation energy of a chemical reaction.<br />
  19. 19. Enzymes<br />Enzymes help organisms maintain homeostasis ( a constant body temperature)<br />Without enzymes, chemical reactions would not occur quickly enough to sustain life. <br />Enzymes speed up the chemical processes in the body.<br />Enzymes are proteins, produced by different<br /> cells of humans, animals, plants and<br /> microorganisms, which accelerate the<br /> rate of chemical reactions in living organisms.<br /> Like all catalysts, enzymes work by lowering<br /> the amount of activation energy needed for a<br /> reaction to occur and thus dramatically <br />accelerating the rate of the reaction.<br />
  20. 20. Enzyme Specificity<br />A substance on which an enzyme acts during chemical reaction is called a substrate.<br />Enzymes act only on specific substrates.<br />For example, the enzyme amylase works only to breakdown starch to glucose.<br />In this reaction, starch is amylase’s substrate.<br />
  21. 21. Enzymes<br />An enzyme’s shape determines it’s activity. <br />Typically, an enzyme is a large protein with one or more deep folds in it’s surface. <br />
  22. 22. Enzymes<br />These folds form pockets called active sites.<br />An enzyme’s substrate fits into the active site. <br />An enzyme acts only on a specific substrate because only that substrate fits into it’s active site.<br />
  23. 23. Enzymes<br />When an enzyme first attaches to a substrate during a chemical reaction, <br />the enzyme’s shape changes slightly so that the substrate fits more tightly in the enzyme’s active site.<br />
  24. 24. Enzymes<br />At an active site, an enzyme and a substrate interact in a way that reduces the activation energy of the reaction, making the substrata more likely to react.<br />This makes it so far less activation energy is required for the reaction, therefore speeding up the reaction process.<br />
  25. 25. Enzymes<br />The reaction is complete when products have formed. <br />The enzyme is now free to catalyze further reactions<br />
  26. 26. Factors Enzyme Activity<br />Any factor that changes the shape of an enzyme can affect the enzyme’s activity. <br />For example, enzymes operate most efficiently within a certain range of temperatures.<br />Temperature’s outside an enzyme’s range can either break or strengthen some of the enzyme’s bonds, changing it’s shape.<br />
  27. 27. Factors Enzyme Activity<br />Enzymes also operate best within a certain range of pH values.<br />A ph value outside of this normal range can cause enzymes to weaken and break, reducing or eliminating the enzyme’s effectiveness.<br />The enzymes that are present at any given time in a cell determine what happens in that cell. <br />
  28. 28. Factors Enzyme Activity<br />Your body’s cells contain many kinds of enzymes and each enzyme sets off a particular type of special chemical reaction.<br />Different kinds of cells contain different kinds of enzymes that are specific to that cell’s function.<br />The enzymes present in nerve cells will be different combinations of enzymes than those found in blood cells in your body.<br />

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