Bio 100 Lesson 6 Enzymes PDF

ES YM 0 5 Z CH. N E 6 N DE S S O NL A0 0...

ES YM 0 5 Z CH. N E 6 N DE S S O NL A0 0 Y 1 GB I O ER EN  LESSON OBJECTIVES 1. To be able to define work, energy and state the major forms of energy. 2. To be able to list the major types of chemical reactions in living systems. 3. To be able to differentiate between spontaneous and non-spontaneous reactions. 4. To be able to define activation energy and state its importance. 5. To be able to define the term enzyme. 6. To be able to state the composition, functions and characteristics of enzymes. 7. To be able to explain how different factors affect enzyme activity. 8. To be able to explain how cells couple endergonic reactions to exergonic reactions. 9. To be able to state the role of ATP to cells.  CHEMICAL REACTIONS What are Chemical Reactions:  Processes where substances are changed into other substances  Examples:  When molecules are build.  When molecules are broken down.  Rearrangement of atoms in a molecule. Metabolism:  The sum total of all reactions in a cell. SECTION 6.1 Energy Chemical Reactions Enzymes  ENERGY AND LIFE Examples of Energy and Work:  Winding clock  Music box Why Life Needs Energy:  Because biological work requires energy  To move materials.  To assemble large molecules (macromolecules). What is the Ultimate Source of Energy?  Sun Direction of Energy Flow:  Energy always flow downhill.  Energy cannot be reused. THE DEFINITION OF ENERGY AND WORK What is Energy?  It is the capacity to do work, OR  It is the capacity to cause any change in state or motion of matter, OR  The ability to promote change The Two Forms of Energy:  Potential energy  Kinetic energy  HEAT AND MECHANICAL ENERGY AND UNITS OF ENERGY Heat Energy:  Energy that flows from high temperature (the source) to low temperature (the sink). Mechanical energy:  Energy in the movement of matter. Units of Energy  Kilojoule (kJ)  Kilocalorie (kcal) ENERGY CONVERSIONS IN LIVING SYSTEMS What is Free Energy?  Free energy is the energy that is released by a chemical reaction. How do Cells use Free Energy? 1. Cell movement. 2. Cell transport. 3. Cell reproduction. 4. Assembling of complex molecules.  POTENTIAL ENERGY What is Potential Energy?  Energy possessed by a body due to its position. Physical Examples of Potential Energy: 1. A roller coaster at the top. 2. A stretched rubber band or pulled bow string. 3. An extended or compressed spring. 4. Water behind a dam. 5. Concentration gradient. Note: Biological molecules have “chemical potential energy” in their chemical bonds. Ref. Fig 6.1 p 118  KINETIC ENERGY What is Kinetic Energy?  Energy possessed by a moving object.  A swinging base-ball but has kinetic energy.  Moving molecules in a cell have kinetic energy also. Note:  Living organisms always convert energy from one form to another.  Some energy is used for cellular work. THERMODYNAMICS AND THE LAWS OF THERMODYNAMICS? Thermodynamics:  Thermodynamics is the study of energy conversions. Laws of Thermodynamics:  Two laws that govern energy conversions in the universe.  THE FIRST LAW OF THERMODYNAMICS First Law of Thermodynamics:  Energy cannot be created or destroyed.  *Energy can be transferred or transformed.  The total amount of energy in the universe remain constant. Note:  The first law is also known as the law of energy conservation. THE SECOND LAW OF THERMODYNAMICS The Second Law:  All objects in the universe tend towards disorder or randomness.  OR  The transfer or transformation of energy increases disorder or entropy. What is Entropy?  The measure of randomness is called entropy. ENERGY CONVERSIONS HYDRO-ELECTRIC DAM ENERGY CONVERSIONS  ENTHALPY, FREE ENERGY AND ENTROPY Enthalpy (H):  The total amount of energy. Free Energy (G):  The usable energy or energy that can be used to do work. Entropy (S):  The unusable energy. The Energy Equations:  H = G + TS OR G = H - TS TYPES OF ENERGY THAT ARE USEFUL TO BIOLOGY 1. Light energy 2. Heat energy 3. Mechanical energy 4. Chemical energy 5. Electrical energy Ref. Table 6.1 p119  6.2: ENZYMES AND RIBOZYMES What are Enzymes?  Proteins that catalyze metabolic reactions and make them run faster.  Without enzymes, spontaneous reactions would run very slowly. What are Ribozymes?  Catalytic RNAs are known as ribozymes. What are Metabolic Reactions?  Reactions that occur in living organisms; (anabolic and catabolic reactions).  HOW ENZYMES SPEED UP REACTIONS Reduction of Activation Energy:  Enzymes reduce the activation energy, this greatly speed up metabolic reactions.  Enzymes bring reactants close together and hence facilitate the reaction. What are Substrates?  The reactant/s or substances acted upon by the enzyme. What are Products?  Changed reactants.  HOW ENZYMES SPEED UP REACTIONS Fig 6.4 p121  HOW ENZYMES ACT Fig 6.5 p122  THE ACTIVE SITE OF AN ENZYME What is the Active Site?  The point on the enzyme where the substrate is bound. How big is the Active Site?  The active site forms just a small part of the enzyme. Structure of the Active Site:  The structure of the active site is complimentary to that of the substrate (e.g. the glove and hand relationship) THE ACTIVE SITE  ENZYME SPECIFICITY What is Enzyme Specificity?  Each enzyme can act on a specific kind of substrate.  Each enzyme catalyzes a particular kind of reaction. How are Enzymes Named?  Enzymes are named by adding the prefix –ase to the reaction it catalyzes. Examples:  Deaminase – removes amino groups.  Decarboxylase – removes carbon dioxide.  Kinase – transfers a phosphate group.  FACTORS THAT AFFECT ENZYME ACTIVITY 1. Temperature 2. pH 3. Activators 4. Inhibitors  TEMPERATURE Effect of Very High Temperatures:  Very high temperature denature proteins (enzymes). This destroys their 3-D structure. Effect of Very Low temperatures:  Low temperature reduce kinetic energy of reactants.  This slows down the rate of any reaction. What is Optimum Temperature?  Temperature at which the enzyme performs best or the right temperature for the enzyme. THE EFFECT OF TEMPERATURE ON ENZYME ACTIVITY Fig. 6.7 p125.  VARIATIONS IN OPTIMUM TEMPERATURES Hot Springs:  Organisms adapted to life in the water of hot springs have enzymes with high optimum temperatures.  Only a few types of hardy bacteria. Icy Conditions:  Organisms that live in very cold conditions have enzymes with very low optimum temperatures.  THE EFFECT OF PH ON ENZYME ACTIVITY Effects of Very Low and Very High pH:  Affect the ionization states of various charged groups.  This interferes with the interactions between reactants and enzymes.  Extreme pH values too can damage the 3-D structure of enzymes.  All the above can slow down or stop enzyme action. THE EFFECT OF PH ON ENZYME ACTIVITY  THE OPTIMUM PH What is the Optimum pH?  The pH at which the enzyme performs best.  Most enzymes work best at or around neutral pH. Variations in Optimum pH.  Optimum pH varies according to the environment under which the enzyme operates.  Trypsin work in the acidic stomach -- it has a very low optimum pH.  THE EFFECT OF ENZYME ACTIVATORS What are Enzyme Activators?  Substances that bind to enzymes and activate them.  Activators include cofactors and coenzymes. What are Cofactors?  Inorganic substances that activate enzymes e.g. Fe2+ and Mg+  We get these from minerals in our food. What are Coenzymes?  Organic substances that activate enzymes.  Coenzymes are derived from vitamins, in fruits and vegetables.  ENZYME INHIBITORS What are Enzyme Inhibitors?  Substances that interfere with enzyme activity. Types of Inhibitors: 1. Competitive Inhibitors. 2. Non competitive Inhibitors. 3. End-products as Inhibitors.  COMPETITIVE INHIBITORS Competitive inhibitors:  Substances that bind to active site and block the binding of the substrate.  In this way, the inhibitor competes with substrate for the active site. Note:  Competitive inhibitors are substances with a molecular structure that is very similar to that of the natural substrate of the enzyme. How to Reduce competitive Inhibition:  Competitive inhibition can be corrected by increasing the concentration of the substrate. NONCOMPETITIVE INHIBITION Noncompetitive Inhibitors:  Substances that interfere the 3-D structure of the enzyme and disables it.  Most noncompetitive inhibitors form covalent bonds with the enzyme and permanently inactivate it. Examples of Noncompetitive Inhibitors:  Lead  Penicillin  END-PRODUCT INHIBITION (NEGATIVE FEEDBACK) End-product Inhibition:  This occurs when the end product inhibits a key enzyme in the pathway that synthesizes it.  Accumulation of end-product shuts down the reaction producing it.  Depletion of end-product allow reaction to run. THE MECHANISM OF END- PRODUCT INHIBITION  WHAT IS THE IMPORTANCE OF END-PRODUCT INHIBITION? The Importance of End-product Inhibition:  It allows for self-regulation or negative feedback inhibition. Physical Examples of Negative Feedback Systems.  Thermostats.  Car cruise control.  REVIEW QUESTIONS 1. List the types of reaction? 2. List the laws of thermodynamics. 3. Give an example of an anabolic reaction. 4. What is an exergonic reaction? 5. What is energy? List the types of energy. 6. What is an enzyme? How is an enzyme different from a ribozyme? 7. What is activation energy? 8. How is competitive inhibition different from non- competitive inhibition? 9. Define optimum temperature and state how too high temperatures interfere with enzyme activity. 10. List the factors that affect enzyme activity 11. State the importance of end-product inhibition to living organisms.