Enzyme Biology and Regulation
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Questions and Answers

What is the primary function of an enzyme's active site?

  • To change the pH of the environment
  • To lower the activation energy
  • To break down the substrate
  • To bind to the substrate (correct)

    • What is induced fit in the context of enzymes?

  • An increase in the enzyme's activity
  • A permanent change in the shape of the enzyme
  • A temporary change in the shape of the active site (correct)
  • A change in the substrate's shape

    • What is the effect of temperatures above the optimum on enzyme activity?

  • It decreases the enzyme's activity
  • It has no effect on the enzyme's activity
  • It causes the enzyme to denature (correct)
  • It increases the enzyme's activity

    • What is the role of cofactors in enzyme catalysis?

    <p>To facilitate the enzyme's catalytic activity</p> Signup and view all the answers

    What is the difference between competitive and non-competitive inhibitors?

    <p>Competitive inhibitors bind to the active site, while non-competitive inhibitors bind away from the active site</p> Signup and view all the answers

    What type of proteins are responsible for transferring phosphate groups from ATP?

    <p>Kinases</p> Signup and view all the answers

    What is the effect of pH on enzyme activity?

    <p>It decreases the enzyme's activity at pH's above or below the optimum</p> Signup and view all the answers

    What is the role of lysozyme in the body?

    <p>It breaks down oligosaccharides in bacterial cell walls</p> Signup and view all the answers

    What is the effect of phosphorylation on some enzymes?

    <p>It can either activate or deactivate them</p> Signup and view all the answers

    What is the term for the process of adding a phosphate group to an enzyme?

    <p>Phosphorylation</p> Signup and view all the answers

    What is the effect of irreversible inhibitors on enzymes?

    <p>They bind irreversibly to the active site</p> Signup and view all the answers

    What is the function of glycogen phosphorylase in wood frogs?

    <p>To release glucose from glycogen</p> Signup and view all the answers

    What is the role of feedback inhibition in enzyme regulation?

    <p>It regulates the enzyme's activity based on the concentration of the product</p> Signup and view all the answers

    What is the adaptation that helps wood frogs from Alaska survive colder temperatures?

    <p>They can increase their glycogen phosphorylase activity in response to cold temperatures</p> Signup and view all the answers

    What is the effect of enzymes on the activation energy of reactions?

    <p>They decrease the activation energy of both exergonic and endergonic reactions</p> Signup and view all the answers

    What is the role of urea in wood frogs during winter?

    <p>It acts as an antifreeze, along with glucose</p> Signup and view all the answers

    What is the primary function of allosteric control in enzyme regulation?

    <p>To stabilize the active or inactive form of an enzyme</p> Signup and view all the answers

    What is the purpose of feedback inhibition in metabolic pathways?

    <p>To regulate the activity of enzymes in a pathway</p> Signup and view all the answers

    What is the role of repressor proteins in genetic control?

    <p>To inhibit gene expression</p> Signup and view all the answers

    How does covalent control regulate enzyme activity?

    <p>By phosphorylating or dephosphorylating proteins</p> Signup and view all the answers

    What is the time scale of genetic control in enzyme regulation?

    <p>Seconds to minutes</p> Signup and view all the answers

    What is the difference between allosteric activators and inhibitors?

    <p>Activators stabilize the active form, while inhibitors stabilize the inactive form</p> Signup and view all the answers

    What is the relationship between the end product of a metabolic pathway and feedback inhibition?

    <p>The end product can inhibit an enzyme in its pathway</p> Signup and view all the answers

    What is the primary function of enzyme control in cells?

    <p>To regulate metabolic pathways</p> Signup and view all the answers

    What percentage of oxygen breathed in is used for electron transport chain?

    <p>90%</p> Signup and view all the answers

    What is the primary function of cytochrome c in the electron transport chain?

    <p>To shuttle electrons between Complex 1 and Complex 3</p> Signup and view all the answers

    What is the number of large protein complexes in the inner mitochondrial membrane involved in the electron transport chain?

    <p>4</p> Signup and view all the answers

    What is the other name for coenzyme Q, an electron carrier in the electron transport chain?

    <p>Ubiquinol</p> Signup and view all the answers

    What is the approximate length of the cytochrome c protein?

    <p>100-104 amino acids</p> Signup and view all the answers

    What is the cofactor found in cytochromes, involved in the electron transport chain?

    <p>Heme with a central Fe atom</p> Signup and view all the answers

    What is the purpose of NADH and FADH2 in the electron transport chain?

    <p>To pass electrons to the electron transport chain</p> Signup and view all the answers

    What is the end result of the electron transport chain in the mitochondrial inner membrane?

    <p>Synthesis of ATP through oxidative phosphorylation</p> Signup and view all the answers

    During oxidative phosphorylation, what is the primary function of Complex 1, 3, and 4?

    <p>To generate a proton gradient</p> Signup and view all the answers

    What is the net result of the electron transport chain in terms of protons?

    <p>10 protons moved from the matrix to the intermembrane space</p> Signup and view all the answers

    What is the function of cytochrome c in the electron transport chain?

    <p>To receive electrons from Coenzyme Q</p> Signup and view all the answers

    What is the energy currency of the cell that is generated during oxidative phosphorylation?

    <p>ATP</p> Signup and view all the answers

    What is the primary function of cytochrome c in the electron transport chain?

    <p>To transfer electrons to oxygen</p> Signup and view all the answers

    What is the role of uncouplers in mitochondria?

    <p>To move protons back across the membrane, not through ATP synthase</p> Signup and view all the answers

    What is the net ATP yield from the complete oxidation of one glucose molecule?

    <p>32 ATP</p> Signup and view all the answers

    Which protein complex in the inner mitochondrial membrane is involved in the transfer of electrons from NADH to coenzyme Q?

    <p>Complex I</p> Signup and view all the answers

    What is the function of ATP synthase in the electron transport chain?

    <p>To convert the energy of the proton gradient into ATP</p> Signup and view all the answers

    What is the primary consequence of the electron transport chain?

    <p>The reduction of oxygen to water</p> Signup and view all the answers

    What is the electron carrier that receives electrons from NADH and FADH2?

    <p>Coenzyme Q</p> Signup and view all the answers

    What is the role of cytochrome c in evolutionary studies?

    <p>To construct phylogenetic trees</p> Signup and view all the answers

    What is the primary function of the electron transport chain?

    <p>To generate a proton gradient</p> Signup and view all the answers

    What is the result of the movement of electrons through the electron transport chain?

    <p>The pumping of protons across the inner mitochondrial membrane</p> Signup and view all the answers

    What is the role of cytochrome b in the electron transport chain?

    <p>To pump protons across the inner mitochondrial membrane</p> Signup and view all the answers

    What is the energy-rich molecule that is generated during the electron transport chain?

    <p>Proton gradient</p> Signup and view all the answers

    Study Notes

    Enzymes and Catalysis

    • Enzymes lower the activation energy of both

      Enzymes and Catalysis

      • Enzymes lower the activation energy of both Exergonic reactions release energy spontaneously.which require energy and do not occur spontaneously.
      • The active site of an enzyme is where a substrate binds, and it can change shape when a substrate enters - induced fit.

      Active Site

      • Typically, there is a close shape match between the active site and substrate (lock and key) - specificity, ensuring that the enzyme only catalyzes a specific reaction.
      • The active site is a three-dimensional region with a unique shape and chemical properties that allows it to bind to a specific substrate, positioning it for a chemical reaction to occur.

      reactions.

    • The active site of an enzyme is where a substrate binds, and it can change shape when a substrate enters - induced fit.

    Active Site

    • Typically, there is a close shape match between the active site and substrate (lock and key) - specificity.
    • The active site is a cleft or crevice where catalysis takes place.
    • The shape of the active site can change as the substrate enters - induced fit, forming the enzyme-substrate complex.

    Enzyme Catalysis Strategies

    • Enzymes may form covalent bonds with the substrate itself.
    • General strategies of enzyme catalysis include various ways to lower the activation energy.

    Temperature and pH Effects

    • Temperature and pH affect reaction rates; temperatures below or above the optimum canreduce enzyme activity by altering the enzyme's conformation, obstructing active site access, or disrupting essential electrostatic interactions, which are crucial for maintaining the enzyme's active site geometry and facilitating substrate binding. These interactions can be disrupted by pH changes, leading to a decrease in enzyme activity. Optimal pH ranges for enzyme activity can vary greatly, with some enzymes being active in acidic conditions (e.g., pepsin in the stomach) and others in alkaline conditions (e.g., trypsin in the small intestine). Temperature and pH effects are often enzyme-specific, making it essential to understand the optimal conditions for a particular enzyme to function efficiently.
    • pH changes can affectpH changes affect enzyme activity by altering amino acid residues' protonation states, influencing charges, conformation, and substrate binding. pH-dependent protonation states can enhance or hinder enzyme-substrate interactions, modulating activity and thermo-stability.

    Cofactors

    • Cofactors are non-protein molecules that bind to enzymes, enabling them to perform their biological functions. These molecules can be either inorganic (e.g., metal ions like zinc, iron, or copper) or organic (e.g., flavin or heme groups). Cofactors can modulate enzyme activity by influencing the active site's shape, participating in catalysis, or facilitating the transfer of electrons. In some cases, cofactors are tightly bound to the enzyme, while in others, they are loosely associated or even diffuse into the enzyme's active site during catalysis. Examples of enzymes requiring cofactors include carbonic anhydrase (which uses zinc) and lactate dehydrogenase (which uses NAD+). The presence or absence of cofactors can significantly impact enzyme activity, underscoring their critical role in maintaining proper enzyme function.are required for catalysis in some enzymes, including inorganic ions (e.g., Fe, Zn, Cu) and complex organic molecules (coenzymes, e.g., vitamins, NAD+, FAD).

    Enzyme Inhibition

    • Inhibitors can be drugs, toxins, or normal metabolites that regulate activity.
    • Types of inhibitors include:
      • Irreversible inhibitors (bind covalently, e.g., penicillin)
      • Reversible inhibitors:
        • Competitive inhibitors (bind to active site)
        • Non-competitive inhibitors (bind away from active site)

    Enzyme Control

    • Control mechanisms include:
      • Allosteric control (fast, <1 sec): molecule binds away from active site, stabilizing active or inactive forms
      • Covalent control (relatively fast, <1 sec): phosphorylation and dephosphorylation of enzymes
      • Genetic control (slower, seconds-minutes): regulation of enzyme expression

    Feedback Inhibition

    • Feedback inhibition occurs when the end product of a metabolic pathway inhibits an enzyme that catalyzes an earlier reaction in the pathway.

    Examples of Enzyme Control

    • In frogs, glycogen phosphorylase is regulated by both allosteric and covalent control mechanisms, involving phosphorylation and dephosphorylation.
    • Wood frogs release glucose from glycogen as they freeze in winter, and this regulation is essential for their survival.

    Cytochrome c in Evolutionary Studies

    • Cytochrome c is used in evolutionary studies to construct clades, as its amino acid sequence varies slightly between species, allowing researchers to reconstruct phylogenetic relationships and infer evolutionary histories.
    • It is a highly conserved protein, with humans and chimps having identical cytochrome c, and rhesus monkeys differing by only one amino acid

    Electron Transport Chain

    • Electrons lose energy as they move towards electronegative O2
    • Electrons pass through various cofactors and coenzymes, resulting in the reduction of O2 to water
    • About 90% of oxygen breathed in is used in this process

    Electron Transport Chain Complexes

    • The electron transport chain consists of 4 large protein complexes in the inner mitochondrial membrane
    • Complexes 1, 2, 3, and 4 are involved in the process
    • Q (ubiquinol/ubiquinone/coenzyme Q) and cytochrome c are two electron carriers involved in the process

    Cytochrome c

    • Cytochrome c is a small, well-conserved protein throughout evolution
    • It is 100-104 amino acids long and contains a heme with a central Fe atom as a cofactor
    • Cytochromes are redox-active proteins involved in electron transport and redox catalysis

    Electron Transport Chain and Oxidative Phosphorylation

    • The electron transport chain generates a proton gradient, which is a form of potential energy
    • The gradient is used to drive the production of ATP through the process of chemiosmosis
    • ATP synthase forms a pathway for protons to move down their electrochemical gradient, generating ATP

    Uncouplers

    • Uncouplers are proteins that move protons back across the membrane, bypassing ATP synthase
    • This process converts potential energy to kinetic energy (heat), and is used in certain cells to generate heat

    ATP Yield and Fermentation

    • The complete breakdown of glucose produces approximately 32 ATPs
    • In the absence of oxygenIn contrast to the efficient process of cellular respiration, which generates approximately 36-38 ATP molecules from one glucose molecule, fermentation (anaerobic respiration), occurring in the absence of oxygen, yields only 2 ATP molecules per glucose molecule. This process takes place in the cytosol and is characteristic of muscle cells when they are subjected to intense, short-duration exercises. During fermentation, glucose is converted into lactic acid, producing a net gain of 2 ATP molecules through substrate-level phosphorylation. Notably, this process does not involve the electron transport chain or oxidative phosphorylation, unlike cellular respiration. occurs
    • Other catabolic pathways are also available for energy production

    Getting Energy from Fats

    • Fats are a major source of energy storage in humans and other mammals
    • β-oxidation occurs in the mitochondrial matrix, producing 3 NADH, 1 FADH2, and 1 ATP per acyl unit
    • The energy yield from fats is much higher than from carbohydrates

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    Description

    This quiz covers the basics of enzyme biology, including active sites, induced fit, and optimal pH and temperature. It also explores various types of inhibitors and regulatory mechanisms.

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