The rate of an enzyme catalyzed reaction depends :

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upon substrate concentration and pH, but not on temperature.

only on substrate concentration and pH, but not on temperature.

only on pH and temperature, but not on substrate concentration.

only on temperature, but not on pH and substrate concentration.

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Answer is Wrong!

This question was previously asked in

UPSC CAPF – 2023

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The rate of an enzyme-catalyzed reaction is influenced by multiple factors. Substrate concentration is a key factor, as the rate typically increases with substrate concentration until enzyme saturation is reached (Michaelis-Menten kinetics). pH affects the ionization state of amino acid residues in the enzyme’s active site and the substrate, influencing enzyme-substrate binding and catalysis; enzymes have optimal pH values. Temperature affects the kinetic energy of molecules, increasing reaction rates with increasing temperature up to an optimum, after which the rate decreases sharply due to enzyme denaturation. Therefore, the rate depends on substrate concentration, pH, and temperature. Option A states the rate depends “upon substrate concentration and pH, but not on temperature”. While the premise that the rate does *not* depend on temperature is scientifically incorrect, among the given options, Option A acknowledges dependence on two crucial factors (Substrate concentration and pH). However, it must be stated that the rate *also* depends significantly on temperature. The phrasing of the options appears flawed as dependence on temperature is a fundamental aspect of enzyme kinetics. Assuming there is an intended correct answer among the choices, Option A includes dependencies on two critical factors, even though its exclusion of temperature is incorrect.

– Enzyme reaction rate depends on substrate concentration, pH, and temperature.
– Substrate concentration affects the frequency of enzyme-substrate collisions and active site saturation.
– pH affects the ionization states of enzyme and substrate, influencing activity.
– Temperature affects molecular kinetic energy and enzyme stability (denaturation).

The relationship between reaction rate and substrate concentration is described by models like the Michaelis-Menten equation. Temperature dependence follows the Arrhenius equation up to the optimal temperature. pH dependence is often represented by a bell-shaped curve. All three factors are interdependent and influence the overall enzyme activity and reaction rate. The provided options contain a significant scientific inaccuracy by claiming the rate does not depend on one of the listed factors. Assuming this is a question from a specific exam where A was marked correct despite the flaw, the justification focuses on the factors mentioned in A.

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