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Quiz 4 Part 2

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Justine C.
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10 Questions

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

All of the above

How does phosphorylation of a protein affect its activity?

could increase or decrease the activity

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

Enzymes reduce the free energy of the products of the reaction.

The word "nucleoside" refers to_______.

the nitrogen base and sugar ring

Disulfide bonds stabilize protein shape outside the cell by__________

covalent bonds between cysteines.

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

The hydrolysis of ATP to ADP caused a conformational change in the protein.

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

confocal microscopy

The function of a feedback mechanism is to

turn on/off the synthesis of a gene or product.

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

The last enzyme in a chain of enzymatic reactions signals to a previous enzyme to stop the enzymatic reaction.

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

affinity chromatography

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

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

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