 Objectives: ◦ Take quiz on energy conversions ◦ Describe how an enzyme works ◦ Complete toothpick enzyme lab  Review Questions: ◦ 1. What does the Law of Conservation of Energy say? ◦ 2. What type of energy conversion does a solar panel on a house carry out?  Other Instructions: Turn in vocab., 11x17  Coloring sheet, and fill-in-the-blank from yesterday

 What happens to chemical bonds during chemical reactions?  How do energy changes affect whether a chemical reaction will occur?  Why are enzymes important to living things?

 Living things are made up of chemical compounds  Everything that happens to an organism is based on chemical reactions

 A process that changes or transforms one set of chemicals into another

 Elements or compounds that enter into a reaction

 Elements or compounds produced by a chemical reaction

 In the blood  In the lungs CO 2 + H 2 0  H 2 CO 3 (carbonic acid) H 2 CO 3  CO 2 + H 2 O Released as you breathe

Energy-Absorbing Reaction Energy-Releasing Reaction Products Activation energy Activation energy Reactants

 The energy that is needed to get a reaction started

 Some chemical reactions are too slow or have activation energies that are too high to make them practical for living tissue  These chemical reactions are made possible by catalysts

 Substance that speeds up the rate of chemical reactions  Work by lowering a reactions activation energy

 Are known as Biological catalysts  Speed up reactions in cells  Very specific name for the reaction is catylzes  Enzyme names always end in - ase

Reaction pathway without enzyme Activation energy without enzyme Activation energy with enzyme Reaction pathway with enzyme Reactants Products

 The reactants of enzyme catalyzed reactions  The active site of the enzyme and the substrate have complementary shapes  Fit like a lock and key

Enzyme – substrate complex

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

 Enzymes are affected by any variable that affects chemical reactions 1. pH 2. Temperature 3. Concentration of enzyme

1. What happens to chemical bonds during chemical reactions Bonds are broken in reactants and new bonds are formed in products 2. Describe the role of energy in chemical reactions some chemical reactions release energy, and other chemical reactions absorb energy. Energy changes determine how easily a chemical reaction will occur

3. What are enzymes, and how are they important to living things? Enzymes are biological catylasts. Cells use enzymes to speed up virtually every important chemical reaction that takes place in cells

4. Describe how enzymes work, including the role of the enzyme substrate complex Substrates, the reactants of an enzyme-catylzed reaction, attach to the enzyme at an active site and form an enzyme – substrate complex. Once the complex is formed, the enzyme helps convert substrate into product

5. A change in pH can change the protein. How might a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key) A change in pH could change the shape of hexokinase. This change would diminish the ability of glucose and ATP to bind to the active site of the enzyme.

 1. Temperature (high and low)  2. pH (generally low)  3. enzyme concentration

In colder temps., the enzyme and substrate are moving slower, so they do not collide as often, causing the rate of the reaction to decrease (less products formed)

 Enzyme is denatured, which means that it changes shape such that it can no longer bind to the substrate

 More enzyme available (higher enzyme concentration = reaction happens faster) more product made

 Low pH tends to break hydrogen bonds, changing the shape of the enzyme (denatured) so that it can no longer bind to the substrate

1. What happens to chemical bonds during chemical reactions Bonds are broken in reactants and new bonds are formed in products 2. Describe the role of energy in chemical reactions some chemical reactions release energy, and other chemical reactions absorb energy. Energy changes determine how easily a chemical reaction will occur

3. What are enzymes, and how are they important to living things? Enzymes are biological catylasts. Cells use enzymes to speed up virtually every important chemical reaction that takes place in cells

4. Describe how enzymes work, including the role of the enzyme substrate complex Substrates, the reactants of an enzyme-catylzed reaction, attach to the enzyme at an active site and form an enzyme – substrate complex. Once the complex is formed, the enzyme helps convert substrate into product

5. A change in pH can change the protein. How might a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key) A change in pH could change the shape of hexokinase. This change would diminish the ability of glucose and ATP to bind to the active site of the enzyme.