Enzyme Function and Activity

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Primary function of enzymes in biological systems

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Enzymes catalyze biochemical reactions, increasing the rate of reaction without being consumed in the process.

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Structural nature of enzymes

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Enzymes are globular proteins with a specific tertiary structure that is (nearly) complementary to their substrates. Substrates bind to the active site of enzymes.

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How enzymes reduce the activation energy of reactions

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Enzymes lower the activation energy required to initiate a reaction by binding to substrates at their active site, straining the bonds in the substrates and facilitating their conversion into products.

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Induced fit model of enzyme-substrate interaction

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According to the induced fit model, substrates initially collide with the enzyme's active site and form an enzyme-substrate complex. This interaction induces slight changes in the shape of the active site, making it more complementary to the substrate, which facilitates the reaction.

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Effect of temperature on enzyme-controlled reactions

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Increasing temperature initially increases the rate of reaction by providing more kinetic energy for successful enzyme-substrate collisions. However, above the optimum temperature, enzymes denature, decreasing the rate as the active site loses its complementary shape.

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Impact of pH on enzyme activity

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Changes in pH away from the optimum can disrupt ionic forces and hydrogen bonds, causing the enzyme's tertiary structure to deform. This alters the shape of the active site, reducing its complementarity to the substrate and decreasing the reaction rate.

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Relationship between substrate concentration and enzyme activity

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Increasing substrate concentration increases the rate of reaction because there are more enzyme-substrate collisions. However, there is a maximum rate when all active sites are occupied (enzyme saturation).

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Effect of enzyme concentration on reaction rate

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Increasing enzyme concentration increases the rate of reaction because there are more enzymes available to catalyze substrate molecules. The rate plateaus when all substrate molecules are instantly converted to products.

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Differentiate between competitive and non-competitive inhibitors.

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Competitive inhibitors bind to the active site of the enzyme, blocking substrates from binding. Non-competitive inhibitors bind to a different site on the enzyme, causing a conformational change that alters the shape of the active site.

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Rate of reaction calculation and significance of the initial rate.

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The rate of reaction is calculated as the change in concentration of products or substrates over time. The initial rate represents the rate of reaction at the start when substrate concentration is highest, providing insights into the fastest possible reaction rate.