Prentice Hall Biology - PowerPoint 7 by 4t1kE0o

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									                  Interest Grabber
  Section 2-4




Matter and Energy

Have you ever sat around a campfire or watched flames flicker in a
fireplace? The burning of wood is a chemical reaction—a process that
changes one set of chemicals into another set of chemicals. A chemical
reaction always involves changes in chemical bonds that join atoms in
compounds. The elements or compounds that enter into a chemical
reaction are called reactants. The elements or compounds produced by a
chemical reaction are called products. As wood burns, molecules of
cellulose are broken down and combine with oxygen to form carbon
dioxide and water vapor, and energy is released.




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 Section:
                  Interest Grabber continued
 Section 2-4




1. What are the reactants when wood burns?


2. What are the products when wood burns?


3. What kinds of energy are given off when wood burns?


4. Wood doesn’t burn all by itself. What must you do to start a fire? What
   does this mean in terms of energy?


5. Once the fire gets started, it keeps burning. Why don’t you need to
   keep restarting the fire?


Go to
Section:
                 Section Outline
 Section 2-4




               2–4   Chemical Reactions and Enzymes
                     A. Chemical Reactions
                     B. Energy in Reactions
                        1. Energy Changes
                        2. Activation Energy
                     C. Enzymes
                     D. Enzyme Action
                        1. The Enzyme-Substrate Complex
                        2. Regulation of Enzyme Activity




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Section:
                                         2-4 Chemical reactions and enzymes


Chemical reactions


•A chemical reaction is a process that changes
one set of chemicals into another set of
chemicals by changing chemical bonds.
•The reactants are the elements or compounds
that enter into a chemical reaction
•The products are the elements or compounds
produced by a chemical reaction.
•On notes label reactants and products




 Go to
 Section:
                      2-4 Chemical reactions and enzymes


Energy in reactions


•Energy is either released or absorbed
when chemical bonds are formed or
broken.
•Activation energy is the energy needed
to get a reaction started.



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 Section:
                       Figure 2-19 Chemical Reactions
  Section 2-4




Energy-Absorbing Reaction                 Energy-Releasing Reaction



                     Products                              Activation
                                                           energy
                Activation energy
                                           Reactants
 Reactants
                                                           Products




 Go to
 Section:
                       Figure 2-19 Chemical Reactions
  Section 2-4




Energy-Absorbing Reaction                 Energy-Releasing Reaction



                     Products                              Activation
                                                           energy
                Activation energy
                                           Reactants
 Reactants
                                                           Products




 Go to
 Section:
                   2-4 Chemical reactions and enzymes


Enzymes


•A catalyst is a substance that speeds up the
rate of a chemical reaction
•An enzyme is a protein that acts as a biological
catalyst
•Enzymes speed up reaction by lowering the
activation energy of the chemical reaction
•Show video 2D

Go to
Section:
                 Effect of Enzymes
 Section 2-4




               Reaction pathway
               without enzyme        Activation energy
                                     without enzyme




               Reactants                         Activation
                                                 energy
                       Reaction pathway
                                                 with enzyme
                       with enzyme


                                                     Products




Go to
Section:
                 2-4 Chemical reactions and enzymes


Enzyme Action


•Substrates are the reactants of enzyme-
catalyzed reactions
•An active site is the site on the enzyme where
the substrate binds.
•The active site and substrates in an enzyme-
catalyzed reaction are often compared to a lock
and key because the active site and substrate
have complementary shapes and the fit is
precise.
 Go to
Section:
                   Figure 2-21 Enzyme Action
 Section 2-4


                        Enzyme                     Glucose
                        (hexokinase)
                                                      Substrates
               ADP
    Products
           Glucose-6-                                 ATP
           phosphate
                 Products
                 are released   Active site
                                Enzyme-substrate       Substrates
                                complex                bind to
                                                       enzyme
                                  Substrates
                                  are converted
                                  into products




Go to
Section:
                   Figure 2-21 Enzyme Action
 Section 2-4


                        Enzyme                     Glucose
                        (hexokinase)
                                                      Substrates
               ADP
    Products
           Glucose-6-                                 ATP
           phosphate
                 Products
                 are released   Active site
                                Enzyme-substrate       Substrates
                                complex                bind to
                                                       enzyme
                                  Substrates
                                  are converted
                                  into products




Go to
Section:
                   Figure 2-21 Enzyme Action
 Section 2-4


                        Enzyme                     Glucose
                        (hexokinase)
                                                      Substrates
               ADP
    Products
           Glucose-6-                                 ATP
           phosphate
                 Products
                 are released   Active site
                                Enzyme-substrate       Substrates
                                complex                bind to
                                                       enzyme
                                  Substrates
                                  are converted
                                  into products




Go to
Section:
                   Figure 2-21 Enzyme Action
 Section 2-4


                        Enzyme                     Glucose
                        (hexokinase)
                                                      Substrates
               ADP
    Products
           Glucose-6-                                 ATP
           phosphate
                 Products
                 are released   Active site
                                Enzyme-substrate       Substrates
                                complex                bind to
                                                       enzyme
                                  Substrates
                                  are converted
                                  into products




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Section:
              Videos




Click a hyperlink to choose a video.
  Atomic Structure
  Energy Levels and Ionic Bonding
  Covalent Bonding
  Enzymatic Reactions
  Video 1




       Atomic Structure




Click the image to play the video segment.
  Video 2




       Energy Levels and Ionic Bonding




Click the image to play the video segment.
  Video 3




       Covalent Bonding




Click the image to play the video segment.
  Video 4




       Enzymatic Reactions




Click the image to play the video segment.
          Go Online




Career links on forensic scientists
Interactive test


Articles on organic chemistry


For links on properties of water, go to www.SciLinks.org and enter the
Web Code as follows: cbn-1022.
For links on enzymes, go to www.SciLinks.org and enter the Web Code
as follows: cbn-1024.
                     Interest Grabber Answers




1. Give an example of solid matter.
   Sample answers: books, desks, chairs
2. Give an example of liquid matter.
   Sample answers: water, milk
3. Give an example of gaseous matter.
   Sample answers: air, helium in a balloon
4. Is all matter visible?
   No
5. Does all matter take up space?
   Yes
                    Interest Grabber Answers




1. Working with a partner, make a list of ten things that have water in them.
   Possible answers: bodies of water, rain and snow, soft drinks and other
   beverages, juicy foods such as fruits, and so on.
2. Exchange your list for the list of another pair of students. Did your lists contain
   some of the same things? Did anything on the other list surprise you?
   Students’ answers will likely be similar, but not exactly alike.
3. Did either list contain any living things?
   Students’ lists may include plants, animals, or other living things.
                    Interest Grabber Answers




1. On a sheet of paper, make a list of at least ten things that contain carbon.
  Students will likely know that charcoal and coal contain carbon. They may
  also list carbohydrates (starches and sugars), oil, gasoline, wood, or carbon
  dioxide.
2. Working with a partner, review your list. If you think some things on your list
   contain only carbon, write “only carbon” next to them.
  Students will say that charcoal and coal contain only carbon. While these
  materials do contain small amounts of other elements, such as sulfur, they
  are composed mostly of carbon.
3. If you know other elements that are in any items on your list, write those
    elements next to them.
  Students may know that many carbon compounds also contain oxygen and/or
  hydrogen.
                   Interest Grabber Answers




1. What are the reactants when wood burns?
   Reactants are oxygen and cellulose.
2. What are the products when wood burns?
   Products are carbon dioxide and water.
3. What kinds of energy are given off when wood burns?
   Light and heat are given off. Some students may also mention sound (the
   crackling of a fire).
4. Wood doesn’t burn all by itself. What must you do to start a fire? What does this
   mean in terms of energy?
   To start a fire, you must light it with a match and kindling. You are giving the
   wood some energy in the form of heat.
5. Once the fire gets started, it keeps burning. Why don’t you need to keep
   restarting the fire?
   Once the fire gets going, it gives off enough heat to start more of the wood
   burning.
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