Enzymology - Part I

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| By Kar
Kar, Assistant Professor (Biochemistry)
Karthikeyan Pethusamy is an assistant professor in the Department of Biochemistry at the All India Institute of Medical Sciences in New Delhi
Quizzes Created: 33 | Total Attempts: 50,084
| Attempts: 1,913
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  • 1/7 Questions
    In the graph shown below, increasing the substrate concentration does not increase the rate of reaction at a certain point because - ProProfs

    In the graph shown below, increasing the substrate concentration does not increase the rate of reaction at a certain point because

    • All of the enzymes are occupied by substrates
    • All of the enzymes have been denatured
    • Both are correct
    • None are correct
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Enzymology - Part I - Quiz
About This Quiz

This Enzymology quiz for NEET assesses knowledge on serine proteases, enzyme specificity, and kinetic properties using Km and Lineweaver-Burk plots. It is designed to test and enhance understanding of enzyme characteristics and their biochemical applications.

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  • 2. 

    Select the mismatched pair regarding enzymes and co-factor

    • Manganese - isocitrate dehydrogenase

    • Copper - cytochrome oxidase

    • Zinc - Carbonic anhydrase

    • Cobalt - vitamin B12

    • Selenium - glutathione peroxidase

    • Molybdenum - xanthine oxidase

    • All are correctly matched.

    Correct Answer
    A. All are correctly matched.
    Explanation
    The given answer states that all the pairs regarding enzymes and co-factors are correctly matched. This means that each enzyme listed is indeed associated with the corresponding co-factor mentioned.

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  • 3. 

    False regarding Km

    • Km = concentration of substrate at ½ Vmax

    • Km is inversely proportional to the affinity

    • Km is increased in non-competitive inhibition.

    • Km is increased in competitive inhibition.

    Correct Answer
    A. Km is increased in non-competitive inhibition.
    Explanation
    Km, or the Michaelis constant, represents the substrate concentration at which the reaction rate is half of Vmax (the maximum velocity). It is a measure of the affinity of the enzyme for its substrate; a lower Km indicates higher affinity, and a higher Km indicates lower affinity.
    A) Km = concentration of substrate at ½ Vmax: This is true and is the definition of Km.
    B) Km is inversely proportional to the affinity: This is true. A lower Km means higher affinity, and a higher Km means lower affinity.
    C) Km is increased in non-competitive inhibition: This is false. In non-competitive inhibition, the Km remains unchanged because the inhibitor affects the enzyme's activity but does not compete with the substrate for the active site.
    D) Km is increased in competitive inhibition: This is true. In competitive inhibition, the Km increases because the inhibitor competes with the substrate for the active site, making it appear as though the enzyme has a lower affinity for the substrate.

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  • 4. 

    Select the Serine protease(s)

    • Chymotrypsin

    • Trypsin

    • Elastase

    • Thrombin

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    Serine Protease contain serine at their active site which is a part of catalytic triad.

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  • 5. 

    Which is an enzyme with low specificity ?

    • Glucokinase

    • Tyrosinase

    • Hexokinase

    • None of the above

    Correct Answer
    A. Hexokinase
    Explanation
    Hexokinase is an enzyme with low specificity because it can phosphorylate a wide range of hexoses, such as glucose, mannose, and fructose. It does not require a specific substrate and can catalyze the phosphorylation of multiple hexose sugars. In contrast, enzymes with high specificity only work on specific substrates and have a narrow range of substrates they can act upon.

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  • 6. 

    False regarding Lineweaver-Burk plot

    • 1/Vo is plotted against 1/[S]

    • 1/[S] is plotted against 1/Vo

    • Km and Vmax can be found.

    • Mechanism of action of enzyme inhibitors can be found

    Correct Answer
    A. 1/[S] is plotted against 1/Vo
    Explanation
    also called dobule reciprocal (1/vo Vs 1/[S]) |
    straight line is obtained |
    intercept on x-axis is equal to -1/Km & intercept on the y-axis is equal to 1/Vmax.

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  • 7. 

    Chemical nature of enzyme

    • Proteins

    • RNA

    • Both

    • None

    Correct Answer
    A. Both
    Explanation
    Enzymes are biological catalysts that speed up chemical reactions in living organisms. They can be either proteins or RNA molecules, depending on the specific enzyme. Some enzymes are made up of proteins, while others are made up of RNA. Therefore, the correct answer is "Both" because enzymes can have a chemical nature of either proteins or RNA.

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  • Jul 10, 2024
    Quiz Edited by
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    Kar
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