Multiple Choice
The best way to increase the reaction rate for an enzyme saturated with substrate is always to:
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6. Enzymes and Enzyme Kinetics
Optimal Enzyme Conditions
Multiple Choice
In humans, alcohol dehydrogenase (ADH) is a cytosolic enzyme that oxidizes ethanol; which pH is closest to its optimal activity under physiological conditions?
A
Approximately pH 10.5–11.5
B
Approximately pH 1.5–2.0
C
Approximately pH 3.0–4.0
D
Approximately pH 7.0–8.0
Verified step by step guidance1
Understand that enzymes, including alcohol dehydrogenase (ADH), have an optimal pH at which their catalytic activity is highest. This optimal pH usually reflects the environment where the enzyme naturally functions.
Recall that human alcohol dehydrogenase (ADH) is a cytosolic enzyme, meaning it operates inside the cytoplasm of cells, where the pH is typically close to neutral, around 7.0 to 7.4.
Recognize that extreme pH values (very acidic like pH 1.5–2.0 or very basic like pH 10.5–11.5) usually denature enzymes or reduce their activity because they disrupt the enzyme's structure and the ionization state of amino acid residues important for catalysis.
Therefore, the optimal pH for ADH activity in humans is expected to be near physiological pH, which is approximately pH 7.0–8.0, as this maintains the enzyme's proper structure and function.
Summarize that the enzyme's optimal activity aligns with the normal cytosolic pH, making the answer 'Approximately pH 7.0–8.0' the most reasonable choice.
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