Chapter 2 - Medium
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Questions and Answers

What is the role of enzymes in chemical reactions?

  • Enzymes act as inhibitors to slow down chemical reactions by increasing the activation energy.
  • Enzymes act as coenzymes to carry chemical groups between different molecules.
  • Enzymes act as catalysts to accelerate chemical reactions by lowering the activation energy. (correct)
  • Enzymes act as substrates to initiate chemical reactions by binding to the active site.

    • What is the function of the active site of an enzyme?

  • It is the specific region of an enzyme where substrate binding occurs. (correct)
  • It is the area of an enzyme that regulates its activity through phosphorylation.
  • It is the site where coenzymes carry out chemical reactions.
  • It is the region of an enzyme that inhibits the substrate from binding.

    • What is allosteric regulation of enzyme activity?

  • Enzymes change shape in response to molecules binding at sites other than the active site. (correct)
  • Enzymes change shape in response to molecules binding at the active site.
  • Enzymes carry out feedback inhibition to regulate their activity.
  • Enzymes inhibit the final product of a metabolic pathway.

    • What is the role of feedback inhibition in enzyme regulation?

    <p>The final product of a metabolic pathway inhibits an enzyme involved early in the pathway.</p> Signup and view all the answers

    What is the primary role of coenzymes like NADH in enzymatic reactions?

    <p>Acting as carriers of electrons in oxidation-reduction reactions</p> Signup and view all the answers

    How does feedback inhibition regulate the activity of enzymes like threonine deaminase?

    <p>By binding the end product to the enzyme and inhibiting its activity</p> Signup and view all the answers

    What is the primary function of ion channels in cell membranes?

    <p>Allowing the passage of inorganic ions across the membrane</p> Signup and view all the answers

    What is essential for maintaining concentration gradients of ions and other substances within the cell?

    <p>Active transport across cell membranes</p> Signup and view all the answers

    What role do coenzymes like FAD play in redox reactions in cellular metabolism?

    <p>Act as electron carriers in redox reactions</p> Signup and view all the answers

    What is covalent modification as a mechanism of enzyme regulation?

    <p>Involving the addition or removal of phosphate groups to/from an enzyme, significantly altering the enzyme's activity</p> Signup and view all the answers

    What is the primary role of carrier proteins in cell membranes?

    <p>Transporting specific substances across the membrane</p> Signup and view all the answers

    Which model attributes a dynamic and selective barrier function to cell membranes?

    <p>Fluid mosaic model</p> Signup and view all the answers

    What is the primary function of coenzymes like NADH in enzymatic reactions?

    <p>Carriers of electrons or specific chemical groups</p> Signup and view all the answers

    How do enzymes regulate their activity through covalent modification?

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

    What type of transport maintains cellular homeostasis through protein channels without cellular energy expenditure?

    <p>Facilitated diffusion</p> Signup and view all the answers

    How do enzymes lower the activation energy of a reaction?

    <p>By providing an alternative pathway with lower energy</p> Signup and view all the answers

    What does the 'fluid' aspect of the fluid mosaic model suggest about membrane components?

    <p>They can move laterally within the layer</p> Signup and view all the answers

    What unique roles do membrane proteins, including ion channels and carrier proteins, play in cellular processes?

    <p>They play unique roles in cellular processes</p> Signup and view all the answers

    What property of the membrane allows for flexibility and dynamic rearrangement of membrane components?

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

    Which type of regulation in enzymes involves attaching or removing a phosphate group from an enzyme?

    <p>Covalent modification</p> Signup and view all the answers

    What do transport mechanisms across cell membranes maintain through active transport and facilitated diffusion?

    <p>Cellular homeostasis</p> Signup and view all the answers

    What do enzymes primarily catalyze reactions by providing?

    <p>An alternative pathway with lower activation energy</p> Signup and view all the answers

    What is the main function of the ion channels and carrier proteins in cell membranes?

    <p>Facilitate the transport of specific substances</p> Signup and view all the answers

    Which of the following best describes active transport across cell membranes?

    <p>Movement of substances against their concentration gradient, requiring energy in the form of ATP</p> Signup and view all the answers

    What is the primary function of cholesterol in cell membranes?

    <p>Maintains fluidity and stability of the membrane</p> Signup and view all the answers

    What do coenzymes primarily do in enzymatic reactions?

    <p>Assist enzymes in their catalytic activity, often acting as carriers for chemical groups or electrons during reactions</p> Signup and view all the answers

    How does feedback inhibition regulate enzyme activity in metabolic pathways?

    <p>Regulates enzyme activity to avoid overproduction of the end product, maintaining metabolic balance</p> Signup and view all the answers

    What does the fluid mosaic model describe the cell membrane as?

    <p>A flexible, dynamic structure composed of a phospholipid bilayer with embedded proteins</p> Signup and view all the answers

    What are integral proteins crucial for in cell membranes?

    <p>Various cellular functions including transport and signaling</p> Signup and view all the answers

    Which of the following is an accurate example of passive transport across a cell membrane?

    <p>The movement of substances from higher to lower concentration without using energy</p> Signup and view all the answers

    What is not a primary role of cholesterol in cell membranes?

    <p>Serve as the primary energy source for membrane functions</p> Signup and view all the answers

    What is not a primary function of coenzymes in enzymatic reactions?

    <p>Act as primary substrates that enzymes act upon</p> Signup and view all the answers

    What does feedback inhibition not do in metabolic pathways?

    <p>Speed up the reaction at the beginning of a pathway</p> Signup and view all the answers

    What is not a function of integral proteins in cell membranes?

    <p>Storage of genetic information for cellular processes</p> Signup and view all the answers

    Study Notes

    Cell Membranes, Enzyme Function, and Regulation

    • Facilitated diffusion is a type of passive transport through protein channels without cellular energy expenditure
    • The fluid mosaic model attributes a dynamic and selective barrier function to cell membranes
    • Enzymes lower the activation energy of a reaction by providing an alternative pathway with lower energy
    • Covalent modification in enzyme regulation involves attaching or removing a phosphate group from an enzyme
    • The 'fluid' aspect of the fluid mosaic model suggests that membrane components can move laterally within the layer
    • Coenzymes like NADH primarily function as carriers of electrons or specific chemical groups in enzymatic reactions
    • Enzymes regulate their activity through covalent modification, such as phosphorylation or dephosphorylation
    • The fluidity of the membrane allows for flexibility and dynamic rearrangement of membrane components
    • Membrane proteins, including ion channels and carrier proteins, play unique roles in cellular processes
    • Transport mechanisms across cell membranes maintain cellular homeostasis through facilitated diffusion and active transport
    • The fluid mosaic model describes cell membranes as dynamic structures providing a selective barrier
    • Enzymes catalyze reactions by providing an alternative pathway with lower activation energy

    Biology Concepts Summary

    • Active transport across cell membranes involves movement of substances against their concentration gradient, from lower to higher concentration, requiring energy typically in the form of ATP.
    • Passive transport describes movement of substances from higher to lower concentration without using energy.
    • Cholesterol in cell membranes maintains fluidity and stability, modulating the tightness of the phospholipid bilayer.
    • Coenzymes are non-protein compounds that assist enzymes in their catalytic activity, often acting as carriers for chemical groups or electrons during reactions.
    • Feedback inhibition in metabolic pathways regulates enzyme activity to avoid overproduction of the end product, maintaining metabolic balance.
    • The fluid mosaic model describes the cell membrane as a flexible, dynamic structure composed of a phospholipid bilayer with embedded proteins, emphasizing its fluid nature and mosaic-like arrangement of molecules.
    • Integral proteins are embedded within the cell membrane and can span its entire width, crucial for various cellular functions including transport and signaling.
    • An example of passive transport across a cell membrane is the movement of substances from higher to lower concentration without using energy.
    • Other options for active transport mechanisms include direct protein synthesis on the cell membrane or storage of genetic information for cellular processes.
    • Cholesterol does not primarily act as a channel for ions, serve as the primary energy source for membrane functions, or play a role in the synthesis of nucleic acids.
    • Coenzymes are not primary substrates that enzymes act upon, proteins that bind to an enzyme to increase its activity, or a type of enzyme that breaks down proteins.
    • Feedback inhibition does not speed up the reaction at the beginning of a pathway, prevent the pathway from producing its final product, or replicate the enzymes involved in the pathway.

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