20 Questions
Which electron acceptor is used for detection of succinate dehydrogenase or lactate dehydrogenase activity?
Methylene blue
What is one of the artificial electron acceptors used for detection of succinate dehydrogenase or lactate dehydrogenase activity?
Dichlorophenolindophenol (DCPI)
Which enzyme activities can be detected using methylene blue and dichlorophenolindophenol (DCPI) as artificial electron acceptors?
Succinate dehydrogenase and lactate dehydrogenase
In which state is dichlorophenolindophenol (DCPI) colorless?
Reduced
What happens when electrons are transferred to dehydrogenase enzymes from succinate or lactate?
The reduction occurs
Which chemical species has the highest redox potential?
DCPI
What is the redox potential of NAD/NADH?
-0.06 V
Which chemical species has the lowest redox potential?
FAD/FADH2
What can protons from FADH2 or NADH be transferred to?
Methylene blue or DCPI
What is the effect of methylene blue or DCPI reduction in the reaction catalyzed by succinate or lactate dehydrogenase?
Gradual discoloration
What are two competitive inhibitors of succinate dehydrogenase?
Malonate and pyrophosphate
Which inhibitor has a similar structure to succinate?
Malonate
What is the role of competitive inhibitors in enzyme reactions?
Compete with the substrate for the enzyme's active site
What is the purpose of the SECOND experiment mentioned in the text?
Localization of enzymes in subcellular fractions of the liver
Which enzymes are specifically targeted for localization in the SECOND experiment?
Succinate dehydrogenase, lactate dehydrogenase, and cytochrome oxidase
What is the role of p-phenylenediamine in the context mentioned?
Acting as an artificial electron donor
How does the redox potential of p-phenylenediamine compare to cytochrome c?
Slightly lower than cytochrome c
What is required for the oxidation of p-phenylenediamine in the presence of oxygen?
Active cytochrome oxidase + sufficient cytochrome c
What indicates the progress of the reaction involving p-phenylenediamine and oxygen?
Color appearance in tubes
What is the dependency for the oxidation of p-phenylenediamine?
Cytochrome oxidase
Study Notes
Enzyme Assays
- Methylene blue and dichlorophenolindophenol (DCPI) are artificial electron acceptors used to detect succinate dehydrogenase or lactate dehydrogenase activity.
Redox Reactions
- Electrons transferred from succinate or lactate to dehydrogenase enzymes reduce DCPI or methylene blue, resulting in a color change.
- DCPI is colorless in its oxidized state.
- The redox potential of NAD/NADH is -320 mV.
Redox Potentials
- The chemical species with the highest redox potential is oxygen (O2).
- The chemical species with the lowest redox potential is NADH.
Proton Transfer
- Protons from FADH2 or NADH can be transferred to oxygen or other electron acceptors.
Enzyme Inhibition
- Oxamic acid and malonate are competitive inhibitors of succinate dehydrogenase.
- Malonate has a similar structure to succinate.
Enzyme Localization
- The second experiment involves localizing succinate dehydrogenase and lactate dehydrogenase in tissue samples.
p-Phenylenediamine
- p-Phenylenediamine is an electron acceptor with a redox potential higher than that of cytochrome c.
- Oxygen is required for the oxidation of p-phenylenediamine.
- The formation of a purple color indicates the progress of the reaction involving p-phenylenediamine and oxygen.
- The oxidation of p-phenylenediamine depends on the presence of oxygen.
Test your knowledge of electron acceptors used in enzyme activity detection with this quiz. Explore the roles of methylene blue and dichlorophenolindophenol (DCPI) in detecting succinate dehydrogenase or lactate dehydrogenase activity.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
