9700 · 3.2
Factors that affect enzyme action flashcards
Revision flashcards for Cambridge 9700 Factors that affect enzyme action (syllabus 3.2). Flip, recall, then mark a real past-paper question.
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What is denaturation?
The irreversible change in the specific three-dimensional structure of a protein (like an enzyme), particularly its active site, due to factors like extreme heat or pH. This results in a loss of biological function.
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What is the 'optimum temperature' for an enzyme?
The temperature at which an enzyme exhibits its maximum rate of catalytic activity. Below this, the rate is slower; above this, the enzyme begins to denature.
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How does pH affect enzyme activity?
pH alters the charges on the R-groups of amino acids, disrupting the ionic and hydrogen bonds that maintain the enzyme's tertiary structure and active site shape. This reduces enzyme-substrate binding away from the optimum pH.
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What is Vmax?
Vmax, or maximum velocity, is the maximum rate of an enzyme-catalysed reaction, which occurs when all enzyme active sites are saturated with substrate.
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What is a 'limiting factor' in enzyme kinetics?
A factor (e.g., substrate concentration, enzyme concentration, temperature) that restricts the rate of a reaction, preventing it from increasing further even if other conditions are favorable.
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What is a competitive inhibitor?
A molecule with a shape similar to the substrate that competes for the enzyme's active site. It can be overcome by increasing substrate concentration. It increases Km but does not affect Vmax.
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What is a non-competitive inhibitor?
A molecule that binds to an enzyme at an allosteric site (not the active site), changing the active site's shape and preventing the substrate from binding effectively. It cannot be overcome by increasing substrate concentration. It decreases Vmax but does not affect Km.
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What is the Michaelis-Menten constant (Km)?
Km is the substrate concentration at which the reaction rate is half of Vmax. It is an inverse measure of the enzyme's affinity for its substrate (a low Km indicates high affinity).