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Which types of molecules are metabolized by Cytochrome P450 enzymes?
Which types of molecules are metabolized by Cytochrome P450 enzymes?
Endogenous and exogenous molecules
What is the role of the heme cofactor in the catalytic cycle of Cytochrome P450?
What is the role of the heme cofactor in the catalytic cycle of Cytochrome P450?
What is the name of the diatomic gas that can bind to reduced cytochromes P450?
What is the name of the diatomic gas that can bind to reduced cytochromes P450?
Oxygen
The binding of the organic substrate precedes the reduction of the heme in the catalytic cycle of Cytochrome P450.
The binding of the organic substrate precedes the reduction of the heme in the catalytic cycle of Cytochrome P450.
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What is the name of the technique commonly used to identify and quantify the heme cofactor and the redox activity of cytochrome P450?
What is the name of the technique commonly used to identify and quantify the heme cofactor and the redox activity of cytochrome P450?
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The ______ equation is used to measure the reduction potentials of a molecule based on its oxidation and reduction states.
The ______ equation is used to measure the reduction potentials of a molecule based on its oxidation and reduction states.
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The reduction potential at which 50% of the molecules are oxidized and 50% are reduced is called the [blank] potential.
The reduction potential at which 50% of the molecules are oxidized and 50% are reduced is called the [blank] potential.
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What is the symbol used to represent the standard electrode potential at pH 7?
What is the symbol used to represent the standard electrode potential at pH 7?
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Match the following terms with their correct definitions.
Match the following terms with their correct definitions.
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The stronger the oxidizing agent, the more positive its reduction potential.
The stronger the oxidizing agent, the more positive its reduction potential.
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The stronger the reducing agent, the more negative its reduction potential.
The stronger the reducing agent, the more negative its reduction potential.
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What technique is used to measure the reduction potential of a molecule?
What technique is used to measure the reduction potential of a molecule?
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The binding of an organic substrate to cytochrome P450 can alter the reduction potential of the heme.
The binding of an organic substrate to cytochrome P450 can alter the reduction potential of the heme.
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Electron transfer from NADPH to cytochrome P450 Fe(III) is possible if the reduction potential of NADPH is more positive than that of cytochrome P450 Fe(III)/Fe(II).
Electron transfer from NADPH to cytochrome P450 Fe(III) is possible if the reduction potential of NADPH is more positive than that of cytochrome P450 Fe(III)/Fe(II).
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What is the critical factor that allows NADPH to reduce cytochrome P450 Fe(III)?
What is the critical factor that allows NADPH to reduce cytochrome P450 Fe(III)?
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What kind of experimental evidence supports the statement that oxygen can bind to reduced cytochrome P450?
What kind of experimental evidence supports the statement that oxygen can bind to reduced cytochrome P450?
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What is the significance of the ordered sequence of events in the catalytic cycle of Cytochrome P450?
What is the significance of the ordered sequence of events in the catalytic cycle of Cytochrome P450?
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What are the two types of enzymes that provide electrons for the reduction of cytochrome P450?
What are the two types of enzymes that provide electrons for the reduction of cytochrome P450?
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Which wavelength range would be most suitable for analyzing the extent of P450 reduction?
Which wavelength range would be most suitable for analyzing the extent of P450 reduction?
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Study Notes
Cytochromes P450
- Cytochromes P450 are enzymes involved in the metabolism of endogenous and exogenous molecules.
- The catalytic mechanism involves a precisely ordered sequence of events to minimize unwanted side reactions of reactive oxygen species.
- One substrate binding may precede others in the catalytic cycle.
- Substrates are bound to the active site.
- Heme cofactors play a role in catalysis.
- Products may be released simultaneously or in a specific order.
- The electrons needed for reactions come from NADPH via Ferredoxin Reductase or Cytochrome P450 oxidoreductase.
- UV-visible absorbance spectroscopy is used to identify the heme cofactor and quantify redox activity.
- A diatomic gas can bind to reduced cytochromes P450.
- R3CH binding precedes the reduction of the heme in the catalytic cycle.
- O₂ binds to the reduced heme.
- The specific mechanism of cytochrome P450 is revealed by experiments using reaction kinetics, binding constants, and redox chemistry.
- The first steps in the catalytic cycle are revealed through UV-visible absorbance spectroscopy.
Catalytic Mechanism
- The enzyme R3CH reacts with oxygen (O2) in the presence of NADPH and H+ to produce R3COH, NADP+, and H₂O.
- R3CH is a hydrophobic/lipophilic compound.
Redox Chemistry
- Oxidation is the loss of electrons; reduction is the gain of electrons.
- The half-reaction identifies the oxidation (loss) and reduction (gain) of electrons in a chemical transformation.
- The potential at which 50% of molecules are oxidized and 50% are reduced defines the electrode potential or reduction potential.
- E°' is the symbol representing electrode potential at a pH of 7, given in volts.
- A positive reduction potential implies greater affinity for electrons.
Experimental Evidence
- UV-visible absorbance spectroscopy is crucial for understanding the role of the cytochrome P450 catalytic cycle.
- UV-visible studies identify the cofactor in cytochrome P450.
- Changes in the UV-Visible spectrum shows the cofactor's redox activity.
- Spectroscopy can define the quantitative parameters of redox activity of cytochrome P450.
Substrate Binding and Reduction Potential
- Addition of organic substrate raises the reduction potential of P450.
- Electron transfer from NADPH to P450 Fe(III) is not possible since the NADP+/NADPH potential is more positive than cytochrome P450 Fe(III/II).
- R3CH binding to P450 causes a change in free energy allowing heme reduction by NADPH to occur.
O₂ Binding to Reduced Cytochrome P450
- O₂ binds only after an organic substrate and electron (e-) are present in the active site.
- This prevents the formation of reactive oxygen species.
- The ordered reaction mechanism minimizes the opportunity for cytochromes P450 to reduce O₂ before binding the organic substrate.
Wavelength Analysis
- Specific wavelengths (A, B, C, D) could be measured to quantify cytochrome P450 reduction.
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Description
This quiz explores the fascinating world of Cytochromes P450, enzymes critical in the metabolism of various molecules. It covers their catalytic mechanisms, substrate binding, and the role of heme cofactors in redox reactions. Test your knowledge on the intricacies of these essential enzymes and their biochemical significance.
