Enzyme Catalysis and Reaction Rates — NEET Biology
📚 Practice ConceptRate can also be called velocity if the direction is specified. Rates of physical and chemical processes are influenced by temperature among other factors. A general rule of thumb is that rate doubles or decreases by half for every 10°C change in either direction. Catalysed reactions proceed at rates vastly higher than that of uncatalysed ones. When enzyme catalysed reactions are observed, the rate would be vastly higher than the same but uncatalysed reaction. For example
Which of the following statements correctly describe the factors affecting enzyme activity? S1. Increasing substrate concentration always linearly increases the velocity of the enzymatic reaction without limit. S2. Enzymes exhibit highest activity at an optimum temperature and pH, with activity declining both above and below these values. S3. Low temperatures can preserve enzymes in a temporarily inactive state, whereas high temperatures can denature them, causing irreversible loss of activity. S4. The active site of enzymes from thermophilic organisms typically denatures above 40°C, similar to human enzymes. S5. Specific chemicals called inhibitors can bind to enzymes and reduce their activity by altering their tertiary structure or competing for the active site.
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Correct answer: B — S2, S3 and S5
S1: Incorrect. With an increase in substrate concentration, the velocity of the enzymatic reaction rises initially but eventually reaches a maximum velocity (Vmax) when all enzyme molecules are saturated with substrate. It does not increase without limit. S2: Correct. Enzymes generally function within a narrow range of temperature and pH, showing highest activity at their specific optimum values. S3: Correct. Low temperatures preserve enzyme structure in an inactive state, while high temperatures destroy enzymatic activity by denaturing the protein. S4: Incorrect. Enzymes isolated from thermophilic organisms are notably stable and retain their catalytic power even at high temperatures (upto 80°-90°C), unlike typical enzymes that denature above 40°C. S5: Correct. Inhibitors are specific chemicals that bind to enzymes, thereby reducing their activity, which can involve altering enzyme shape or competitive binding at the active site. Therefore, statements S2, S3, and S5 are correct.
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