Quiz 4 Part 2
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Questions and Answers

How does binding of a signaling molecule to its receptor affect its activity?

  • Binding may activate the protein.
  • Binding may inactivate the protein.
  • Binding may change its conformation.
  • All of the above (correct)

    • How does phosphorylation of a protein affect its activity?

  • always increases activity
  • always decreases the activity
  • does not affect the activity
  • could increase or decrease the activity (correct)

    • Which of the following is INCORRECT regarding how enzymes lower the activation energy of a reaction?

  • Enzymes encourage the substrates to change shape toward a transition state that favors the reaction.
  • Enzymes align substrates to promote a reaction between them.
  • Enzymes rearrange electrons in the substrates in a way that favors the reaction.
  • Enzymes reduce the free energy of the products of the reaction. (correct)

    • The word "nucleoside" refers to_______.

    <p>the nitrogen base and sugar ring</p> Signup and view all the answers

    Disulfide bonds stabilize protein shape outside the cell by__________

    <p>covalent bonds between cysteines.</p> Signup and view all the answers

    Shown below is the ATP hydrolysis cycle of a motor protein. What sentence BEST describes the state of the motor protein in "C"?

    <p>The hydrolysis of ATP to ADP caused a conformational change in the protein.</p> Signup and view all the answers

    Which method is most suitable for determining the location of a protein inside the cell?

    <p>confocal microscopy</p> Signup and view all the answers

    The function of a feedback mechanism is to

    <p>turn on/off the synthesis of a gene or product.</p> Signup and view all the answers

    Which of the following is true about a negative feedback loop?

    <p>The last enzyme in a chain of enzymatic reactions signals to a previous enzyme to stop the enzymatic reaction.</p> Signup and view all the answers

    Which method is used for separating proteins based on specific interactions with other molecules?

    <p>affinity chromatography</p> Signup and view all the answers

    Study Notes

    Signaling Molecule Receptor Binding

    • Binding of a signaling molecule to its receptor activates or inhibits the receptor's activity, leading to a response in the cell
    • This binding causes a conformational change in the receptor, triggering a signal transduction pathway

    Protein Phosphorylation

    • Phosphorylation of a protein can either activate or inhibit its activity, depending on the protein and the site of phosphorylation
    • This post-translational modification can alter the protein's function, localization, or interactions

    Enzyme Activation Energy

    • Enzymes lower the activation energy of a reaction by forming an enzyme-substrate complex, positioning the substrate for efficient catalysis
    • The incorrect statement is that enzymes alter the free energy change (ΔG) of a reaction

    Nucleoside Definition

    • A nucleoside is a molecule composed of a sugar molecule (ribose or deoxyribose) and a nitrogenous base (A, C, G, T, or U)

    Disulfide Bonds

    • Disulfide bonds stabilize protein shape outside the cell by forming covalent bonds between cysteine residues
    • This strengthens the protein's tertiary structure, making it more resistant to degradation

    Motor Protein ATP Hydrolysis Cycle

    • In state "C" of the ATP hydrolysis cycle, the motor protein is in a bound state to the microtubule, with ADP bound and no Pi released

    Protein Localization

    • The most suitable method for determining the location of a protein inside the cell is fluorescence microscopy
    • This involves tagging the protein with a fluorescent marker, allowing visualization of the protein's distribution

    Feedback Mechanisms

    • The function of a feedback mechanism is to maintain homeostasis, regulating a process to achieve a stable outcome
    • A negative feedback loop counters the original stimulus, reducing the response and promoting stability

    Protein Separation

    • The method used for separating proteins based on specific interactions with other molecules is affinity chromatography
    • This involves binding the protein to a column with immobilized ligands, allowing separation based on specific interactions

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    Description

    Learn about signaling molecule receptor binding and protein phosphorylation, including how they affect cellular responses and protein activity.

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