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Questions and Answers
In allosteric enzymes, where do allosteric activators and inhibitors bind?
What effect do allosteric effectors have on enzyme-substrate affinity?
How do allosteric enzymes usually exhibit substrate binding?
In the 'T' conformation of allosteric enzymes, what is the affinity for substrate?
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What conformation does the first substrate molecule change to upon binding in allosteric enzymes?
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What kind of fashion do allosteric enzymes generally change to the new conformation?
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What is the role of the rate-limiting step in metabolic pathways?
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What happens when the rate-limiting enzyme in a pathway is inhibited?
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How does feedback regulation usually involve the rate-limiting enzyme?
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What is feed-forward regulation associated with?
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Why do regulatory enzymes of pathways usually exist as tissue-specific isozymes?
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What is the function of GK, the low-affinity enzyme found in the liver?
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Which type of enzymes exhibit sigmoidal velocity versus substrate concentration plots?
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What effect do allosteric activators have on enzyme activity?
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Which molecules regulate rate-limiting enzymes in fuel oxidation pathways?
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What is the role of protein kinases in enzyme regulation?
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How do allosteric effectors compare to competitive and noncompetitive inhibitors in terms of regulation?
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What is the purpose of covalent modification in enzyme regulation?
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Which process directly activates or inhibits enzymes?
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What activates muscle glycogen phosphorylase kinase, aiding in ATP synthesis for muscle contraction?
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What influences the activity of G-proteins by increasing GTP hydrolysis?
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What causes conformational changes to activate or inhibit the function of various proteins?
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What initiates a phosphorylation cascade by increasing cAMP levels?
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What regulates various cellular functions through reversible protein association?
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Which family is NOT part of the Ras superfamily of small G-proteins?
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What prevents premature cleavage of proteins at their sites of synthesis or secretion?
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What process involves the regulation of gene transcription, translation, and messenger RNA stabilization?
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Which enzyme's maximal capacity in the liver is increased with continued ingestion of ethanol through induction of gene transcription?
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What are metabolic pathways?
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What may a metabolic pathway have at which an intermediate becomes the precursor for another pathway?
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Study Notes
Regulation of Enzyme Activity and Metabolic Pathways
- The Ras superfamily of small G-proteins is divided into five families: Ras, Rho, Arf, Rab, and Ran.
- These monomeric G-proteins are bound to a lipid membrane through a lipid anchor and regulate the assembly and activity of protein complexes at these sites.
- Proteolytic cleavage is irreversible and involves zymogens, precursor proteins that must undergo proteolytic cleavage to become fully functional enzymes.
- Zymogens prevent premature cleavage of proteins at their sites of synthesis or secretion.
- Enzymes involved in blood clotting, such as fibrinogen and prothrombin, are zymogens that are cleaved to the active form by other proteases.
- Tissues adjust the rate of protein synthesis to vary the amount of different enzymes present.
- Regulation of enzyme synthesis occurs through gene transcription, translation, and messenger RNA stabilization, which can be induced or repressed.
- Protein degradation can be selectively regulated, as seen in skeletal muscle during fasting or infective stress.
- The regulation of enzyme activity controls metabolic pathways and physiologic processes to match the body’s requirements.
- The maximal capacity of MEOS (cytochrome P450-2E1) in the liver is increased with continued ingestion of ethanol through induction of gene transcription.
- Metabolic pathways are a series of sequential reactions catalyzed by separate enzymes, with a common function of converting substrates to end products.
- Each step in a pathway is usually catalyzed by a separate enzyme, and a pathway may have a branch point at which an intermediate becomes the precursor for another pathway.
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Description
Test your knowledge of enzyme activity regulation and metabolic pathways with this quiz. Explore topics such as zymogens, gene transcription, protein degradation, and the role of small G-proteins in regulating enzyme activity.
