CBF | Lectures 9 and 10
CBF | Lectures 9 and 10
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Quiz Questions (11 questions)
1. Enzymes have an active site which is an intricately shaped surface that allows them to specifically bind to substrates and catalyze reactions.
2. In irreversible enzyme inhibition, increasing the concentration of substrate does not affect the reaction rate because the enzyme is permanently inactivated and cannot interact with the substrate.
3. Enzymes do not provide activation energy for reactions; instead, they lower the activation energy required for the reaction to proceed.
4. The relationship between an enzyme and a reactant molecule is a temporary association where the enzyme binds to the substrate, facilitates the reaction, and releases the product without being permanently altered.
5. The enzyme active site catalyzes a chemical reaction, distinguishing it from an antibody-antigen binding site which does not perform catalysis but instead binds to antigens to elicit an immune response.
6. The rate of enzymatic reactions is not affected by molecular weight, as it depends on factors like enzyme concentration, substrate concentration, pH, and temperature.
7. During enzyme kinetics studies, enzyme concentration remains constant to observe the effect of substrate concentration on the reaction rate.
8. A plot of enzyme reaction rate against certain factors like enzyme concentration forms a straight line, indicating a direct proportional relationship.
9. The rate of enzyme-catalyzed reactions increases with temperature until an optimal temperature is reached, beyond which the rate decreases due to enzyme denaturation.
10. Activators increase the rate of enzymatic reactions by enhancing enzyme activity or stability.
11. Inhibitors are inversely proportional to the rate of enzymatic reactions because they reduce enzyme activity by binding to the enzyme and preventing substrate interaction.
Previous Exam Questions (19 questions)
1. The apoenzyme is the protein portion of an enzyme, which is inactive on its own. It requires a non-protein component, such as a cofactor or coenzyme, to form a complete, active enzyme known as a holoenzyme. This structure is crucial for the enzyme's biological activity, as the apoenzyme provides the specific shape and structure necessary for substrate binding.
2. The enzyme synthesized in an inactive form is called a zymogen, which is a precursor that requires a biochemical change to become an active enzyme. This mechanism is crucial in processes where premature enzyme activity could be harmful, such as in digestive enzymes that could damage the tissues where they are produced if activated too early.
3. The effect of a reversible competitive inhibitor can be nullified by increasing the substrate concentration. This is because competitive inhibitors bind to the active site of an enzyme, directly competing with the substrate. By increasing the substrate concentration, there's a higher chance that the substrate will bind to the active site instead of the inhibitor, thus overcoming inhibition.
4. Serum alkaline phosphatase level increases in osteosarcoma, which is a type of bone cancer. Alkaline phosphatase is an enzyme linked to bone metabolism, and its elevated levels can indicate increased bone turnover or bone-related diseases.
5. Creatine phosphokinase isoenzyme is a marker for myocardial infarction, which is commonly known as a heart attack. This enzyme, particularly the MB isoform, is released into the blood when heart muscle cells are damaged, making it a useful marker for diagnosing heart damage.
6. Allopurinol is a specific inhibitor for xanthine oxidase, which is an enzyme involved in purine metabolism. Xanthine oxidase converts xanthine to uric acid, and by inhibiting this enzyme, allopurinol reduces the production of uric acid, helping to treat conditions like gout.
7. The isoenzyme LDH5 is elevated in liver disease. Lactate dehydrogenase (LDH) is an enzyme found in many body tissues, including the liver, and its different isoenzymes can indicate various conditions. LDH5 is particularly associated with liver damage.
8. The inhibitor in the given scenario is a noncompetitive inhibitor, which means it binds to an enzyme at a site other than the active site. This binding alters the enzyme's shape, preventing substrate binding or reducing enzyme activity, regardless of substrate concentration increases.
9. The drug allopurinol is prescribed to inhibit xanthine oxidase in patients presenting with swelling and tenderness of the big toe, a symptom of gout. By inhibiting xanthine oxidase, allopurinol decreases uric acid formation, thus alleviating gout symptoms.
10. A non-specific enzyme inhibitor is a sulfhydryl inhibitor, which can bind to multiple types of enzymes, often by interacting with thiol groups in cysteine residues. This type of inhibition is not selective for a particular enzyme type.
11. Noncompetitive enzyme inhibitors are characterized by their effect on Vmax, without affecting Km. They bind to an enzyme irrespective of substrate presence, reducing the maximum rate of reaction (Vmax) but not altering the binding affinity for the substrate (Km).
12. Methotrexate is a potent anticancer drug that inhibits dihydrofolate reductase, an enzyme crucial for DNA synthesis. By depriving cells of necessary components for DNA replication, methotrexate effectively starves rapidly dividing cells, such as cancer cells.
13. Competitive enzyme inhibition occurs when a molecule, known as the inhibitor, competes with the substrate for binding to the active site of an enzyme, which is a critical mechanism in regulating enzyme activity and can be influenced by factors such as temperature and pH.
14. Malonic acid inhibits succinate dehydrogenase by binding to the active site, mimicking the substrate succinate, and thus interfering with the enzyme's normal function in the Krebs cycle.
15. Allopurinol inhibits xanthine oxidase by competing with xanthine, preventing its conversion to uric acid, which is important in the treatment of gout by reducing hyperuricemia.
16. Methotrexate inhibits dihydrofolate reductase competitively, preventing the conversion of dihydrofolate to tetrahydrofolate, which is essential for DNA synthesis, and thus is used as a chemotherapeutic agent.
17. Sulfonamides act as competitive inhibitors in bacteria by mimicking P-aminobenzoic acid, thereby inhibiting the bacterial enzyme responsible for folic acid synthesis, which is crucial for bacterial growth.
18. Factors affecting enzyme activity include temperature, which can increase enzyme activity up to an optimum point, and pH, which affects the ionization of the enzyme's active site and substrate, impacting the enzyme's ability to catalyze reactions effectively.
19. Enzyme specificity can be categorized into absolute specificity, where an enzyme acts on only one substrate, dual specificity, where an enzyme can act on two different substrates or catalyze two different reactions, and stereo-specificity, where the enzyme is specific to a particular isomer of a substrate.
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**Chapter: Enzymology and Its Clinical Applications** **Introduction to Enzymes** Enzymes are fascinating biological catalysts that drive the multitude of chemical reactions necessary for life. Despite their protein nature, enzymes possess a unique ability to accelerate reactions with remarkable s...
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