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Ch.6   energy   enzymes

Ch.6 energy enzymes






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    Ch.6   energy   enzymes Ch.6 energy enzymes Presentation Transcript

    • Energy and Metabolism KEY WORDS: Energy Free Energy ( Δ G) Potential energy Kinetic energy Enzyme Substrate Activation energy Exergonic reaction Endergonic reaction Catalyst ATP/ ADP
    • Energy
      • The capacity to do work
      • Move matter
    • Energy
      • The capacity to do work
      • Move matter
    • Types of energy
      • Question: __________ is an example of kinetic energy, and __________ is an example of potential energy.
        • Fire; a piece of wood
        • A loaded gun; a flying bullet
        • A rock on top of a hill; a rock rolling down the hill
        • None of these are correct.
        • All of these are correct.
      • Kinetic
      • Potential
    • Chemical Energy
      • Stored in chemical bonds
      -high energy electrons
      • Some molecules store a lot of energy
      • Some molecules much store less
      Carbos, lipids Carbon dioxide, water
    • Chemical Energy
      • Energy can be transferred/transformed
      Sugar + oxygen  carbon dioxide + water + heat C 6 H 12 O 6 + O 2  CO 2 + H 2 O + Energy
    • First Law of Thermodynamics :
      • Energy: neither created nor destroyed
      • Converted from one form to another
      • Exchanged between substances
        • All exchanges of energy increase the entropy of the universe
      • Entropy:
        • Disorder or randomness of a system
      • Heat is most disorganized form of energy
      • Reactions that ↑ entropy happen spontaneously & release energy
      Second Law of Thermodynamics :
    • Two laws of thermodynamics
    • Energy Transformed
    • Exergonic Reactions
      • Release energy
      • “ Spontaneous”
      • Usually breakdown of complex molecules
    • Endergonic Reactions
      • Not “Spontaneous”
      • Usually involve synthesis of complex molecules
      6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
      • Require energy
      + Energy
    • Question: Which of the following reactions is endergonic?
      • CO 2 and H 2 O Glucose
      • Amino acids Proteins
      • Triglycerides Fatty acids
      • Ions moving across membrane from an area of high concentration to an area of low concentration.
    • Question:
      • Which of the following reactions releases energy?
      • CO 2 and H 2 O Glucose
      • Amino acids Proteins
      • Triglycerides Fatty acids
      • Ions moving across membrane from an area of high concentration to an area of low concentration.
    • Coupled Reactions glucose CO 2 + H 2 O Energy Exergonic Endergonic Energy Amino acids Protein Exergonic provides energy for the endergonic
    • Living organisms Metabolism
      • All chemical reactions in an organism
      Anabolism Catabolism
    • Living organisms
      • Capture energy to drive chemical reactions.
      • Convert “raw” energy into usable form
      • Sunlight, food
      Energy Energy ATP
    • The structure and hydrolysis of ATP
    • ATP: the Cell’s Rechargeable Battery
      • ATP energy ADP charged battery dead battery
      • This energy can then be used to run an energy requiring reaction.
    • The ATP cycle
    • According to the first law of thermodynamics, energy
      • is never lost or gained, but is only transformed
      • always requires an ultimate source such as the sun
      • can never be gained, but can be lost
      • can never really be harnessed
      • can never be transformed
    • Each time there is a chemical reaction, some energy is exchanged. According to the second law of thermodynamics, with each exchange
      • Some energy is lost, but other energy is created.
      • Some energy must come from the sun.
      • Some energy is transformed into heat.
      • Energy is gained for future use.
      • Some energy is permanently and completely destroyed.
    • ATP stores energy in the form of
      • mechanical energy
      • heat
      • complex carbohydrates
      • chemical bond energy
      • amino acids
    • The complexity of metabolism
    • Equation: Gibb’s Free Energy Δ G = Δ H – T Δ S Energy available for work All energy Energy NOT available for work
    • The relationship of free energy to stability, work capacity, and spontaneous change
    • Energy changes in exergonic and endergonic reactions
    • Energy profile of an exergonic reaction
    • Disequilibrium and work in closed and open systems
    • Is Δ G for an exergonic reaction positive or negative?
    • What is the difference between: Anabolism Catabolism Metabolism
    • From an energy perspective, when is equilibrium reached?
    • Enzymes KEY WORDS: Enzyme Activation energy Catalyst Substrate Active site Induced fit Coenzyme Allosteric site Competitive inhibitor Noncompetitive inhibitor Feedback inhibition
    • Enzymes and Shape Active Site Induced fit : “Handshake” between substrate and enzyme
    • Activation Energy Activation Energy Net Energy Released
    • Enzymes
      • Proteins that speed up chemical reactions (catalysts)
      • Lower activation energy for a reaction
    • Enzyme reactions can be simplified as:
      • S = Substrates (reactants) enter reaction.
      • P = Product (what you get at the end) result
      • E = Enzymes mediate specific steps
      sucrase sucrose + H 2 O glucose + fructose E + S ES E + P
    • The catalytic cycle of an enzyme
    • Enzymes Key Points :
      • Catalyze reactions
      • Don’t change reactions
      • Same net release/use of energy
      • Enzymes are not changed by reaction
      • Each enzyme catalyzes a specific chemical reaction
    • Enzymes lower the barrier of activation energy
    • Which of the following will lower the activation energy of a reaction in a cell?
      • lowering the temperature
      • lowering the pressure
      • using an enzyme
      • changing the amount of the reactants
      • supplying ATP
    • Which of the following will lower the activation energy of a reaction in a cell?
      • lowering the temperature
      • lowering the pressure
      • using an enzyme
      • changing the amount of the reactants
      • supplying ATP
    • Enzymes
      • accelerate specific chemical reactions
      • are not chemically altered by binding with a substrate
      • lower the activation energy of specific chemical reactions
      • all of the above
      • a and c only
    • 4 Things that Affect Enzyme Activity
      • Substrate concentration
      • Enzyme concentration
      • pH
      • Temperature
      Shape of enzyme (Protein denatured)
    • Environmental factors affecting enzyme activity
    • Enzyme Regulation
      • Enzymes can be turned on and off
      • Regulated by other molecules in the cell
      • Examples:
        • Allosteric regulation
        • Feedback inhibition
        • Inhibitors
    • Inhibition of enzyme activity
    • Allosteric regulation of enzyme activity
    • Feedback inhibition
    • If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is:
      • Add more enzyme
      • Heat the solution
      • Add more substrate
      • Add an allosteric inhibitor
      • Add a noncompetitive inhibitor
    • An enzyme accelerates a metabolic reaction by
      • Altering the overall free energy change for the reaction
      • Making an endergonic reaction occur spontaneously
      • Lowering the activation energy
      • Pushing the reaction away from equilibrium
      • Making the substrate molecule more stable
    • Some bacteria are metabolically active in hot springs because
      • They are able to maintain a cooler internal temperature
      • High temperature facilitates active metabolism w/o need of catalysis
      • Enzymes have high optimal temperatures
      • Enzymes are insensitive to temperature
    • Glycolysis is a metabolic pathway that helps living things extract energy from food. From this we know that glycolysis
      • consists of a series of chemical reactions
      • uses a number of enzymes
      • involves the modification of a series of substrates
      • proceeds by means of each enzyme leaving a succeeding reaction to a different enzyme
      • all of the above