Enzymes and Energetics Quiz
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Questions and Answers

What is the primary role of enzymes in chemical reactions?

  • They increase the activation energy needed for reactions.
  • They lower the activation energy necessary for reactions. (correct)
  • They permanently change the substrates.
  • They provide energy for reactions.

    • How do enzymes typically interact with their substrates?

  • Substrates change shape to fit any enzyme.
  • The shape of the substrate fits into the enzyme’s active site. (correct)
  • Enzymes only work in one specific temperature.
  • One enzyme can interact with multiple different substrates.

    • What is a possible effect of a competitive inhibitor on enzyme activity?

  • It deforms the enzyme's structure.
  • It increases the activation energy required.
  • It enhances the enzyme's catalytic ability.
  • It blocks the active site of the enzyme. (correct)

    • What characterizes allosteric enzymes?

    <p>They consist of four subunits and can be activated or inhibited.</p> Signup and view all the answers

    What factor does NOT influence enzyme activity?

    <p>The color of the substrate</p> Signup and view all the answers

    What happens during feedback inhibition?

    <p>The end product of a pathway inhibits early enzymes in that pathway.</p> Signup and view all the answers

    Which statement about enzyme cofactors is true?

    <p>They include ions or molecules that assist enzyme activity.</p> Signup and view all the answers

    Enzymes are described as what type of molecules in relation to the reactions they assist?

    <p>They act as catalysts and are not consumed.</p> Signup and view all the answers

    What is the rate-limiting reaction in the mevalonate pathway?

    <p>HMG-CoA ➟ Mevalonic acid</p> Signup and view all the answers

    Which form of energy is primarily involved in photosynthesis?

    <p>Solar energy</p> Signup and view all the answers

    What does the First Law of Thermodynamics state?

    <p>Energy can be transferred and transformed but cannot be created or destroyed.</p> Signup and view all the answers

    Which statement about kinetic energy is true?

    <p>It is energy that is actively doing work.</p> Signup and view all the answers

    What effect does increasing entropy have on biological order?

    <p>It decreases biological order.</p> Signup and view all the answers

    Why are statins used in relation to the mevalonate pathway?

    <p>To competitively inhibit HMG-CoA Reductase.</p> Signup and view all the answers

    What is Gibbs free energy (G) characterized as?

    <p>The energy that is available to do work.</p> Signup and view all the answers

    Which of the following is a common misconception regarding energy transformation?

    <p>All forms of energy are equally effective at performing work.</p> Signup and view all the answers

    What does a negative ΔG indicate about a chemical reaction?

    <p>The reaction is spontaneous and releases energy.</p> Signup and view all the answers

    Which of the following represents an endergonic reaction?

    <p>Formation of glucose from carbon dioxide and water in photosynthesis.</p> Signup and view all the answers

    Why are reactions that reach equilibrium not desirable for living organisms?

    <p>They signify that no more work can be done due to ΔG = 0.</p> Signup and view all the answers

    What is the metabolic steady state?

    <p>The condition required to ensure continuous energy input and output.</p> Signup and view all the answers

    During cellular respiration, the free energy released from glucose is primarily used to:

    <p>Recharge ATP and produce heat.</p> Signup and view all the answers

    Which statement is true about exergonic reactions?

    <p>They can occur spontaneously without requiring energy input.</p> Signup and view all the answers

    What is the total change in free energy (ΔG) for the complete metabolism of 1 mole of glucose during cellular respiration?

    <p>-686 kcal/mol</p> Signup and view all the answers

    In the equation ΔG = GFinal – GInitial, what does a positive ΔG indicate?

    <p>The reaction requires energy input to occur.</p> Signup and view all the answers

    Study Notes

    Enzymes and Energetics

    • Enzymes are biological catalysts that accelerate chemical reactions by lowering the activation energy (Ea).
    • Enzymes achieve this by aligning substrate functional groups, stretching substrate bonds, and creating microenvironments.
    • The rate of enzymatic reactions depends on the substrate concentration and the availability of enzyme active sites.
    • Enzymes require cofactors (e.g., ions) and coenzymes (e.g., NAD+) for optimal activity.
    • Enzyme activity is influenced by environmental factors such as temperature, pH, and salinity.
    • Enzymes can be inhibited by competitive inhibitors (block active site) and non-competitive inhibitors (deform active site).
    • Inhibition can be irreversible or reversible.

    Enzyme Affinities and Cycles

    • Enzymes exhibit specificity for substrates due to the complementary shape between the substrate and the enzyme's active site.
    • Enzyme-substrate complexes undergo conformational changes during catalysis, resulting in product formation.
    • A single enzyme molecule can catalyze multiple cycles of the same reaction without being destroyed.

    Activators and Inhibitors

    • Allosteric activators stabilize the active form of allosteric enzymes, while allosteric inhibitors stabilize the inactive form.
    • Feedback inhibitors regulate biochemical pathways by inhibiting enzymes involved in earlier steps, often through reversible non-competitive inhibition.

    Biochemical Pathways

    • Biochemical pathways consist of a series of linked chemical reactions where the product of one reaction serves as the reactant for the next.
    • The rate-limiting reaction in a pathway is the slowest step, often targeted by pharmaceuticals to modify pathway activity.

    Basics about Energy

    • Energy is the capacity to perform work. It can be stored (potential energy) or actively doing work (kinetic energy).
    • Energy exists in different forms: solar, electrical, mechanical, chemical, and heat.
    • Chemical energy is stored within chemical bonds and can be transferred when bonds break.
    • Solar energy has a higher potential to perform work than heat.

    Thermodynamic Laws

    • Thermodynamics studies energy transfer and transformation.
    • The First Law states that energy cannot be created or destroyed, only transferred and transformed.
    • Photosynthesis transforms solar energy into chemical energy, while cellular respiration converts chemical energy into ATP.
    • ATP powers various biological processes.
    • Energy transformations are not 100% efficient, resulting in heat production.
    • The Second Law states that energy transfer during transformation increases the entropy (disorder) of the universe.
    • Biological systems require energy to maintain order and fight against entropy.

    Who Says Energy is Free? (Gibbs Energy)

    • Free energy (G) is the energy available to perform work.
    • Change in free energy (ΔG) indicates energy released (exergonic, negative ΔG) or required (endergonic, positive ΔG).
    • Exergonic reactions are spontaneous as reactants have more free energy than products.
    • Endergonic reactions are non-spontaneous as products have more free energy than reactants.

    Cells Transform Energy

    • Photosynthesis is an endergonic process requiring solar energy to synthesize glucose.
    • Cellular respiration is an exergonic process that releases energy from glucose into ATP and heat.

    Don’t Equilibrate to Live

    • Many chemical reactions are reversible and reach equilibrium where ΔG is zero, resulting in no free energy for work.
    • Biota must maintain a negative ΔG to perform work and survive.
    • The metabolic steady state describes the ongoing process of maintaining a negative ΔG.

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    Related Documents

    Enzymes and Energetics PDF

    Description

    Test your knowledge on enzymes and their role in biological reactions. This quiz covers enzyme kinetics, inhibition, and the environmental factors affecting enzyme activity. Understand how enzymes work and their significance in biochemical processes.

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