Enzyme Specificity in Lock and Key Hypothesis

Steps:

• Recall the lock and key hypothesis: enzymes have active sites shaped precisely for specific substrates, like a lock fitting only one key.
• Identify the property it explains: the specificity of enzymes to particular reactions or substrates.
• Evaluate options: check which describes enzyme-substrate matching rather than composition, temperature, or activity levels.
• Select D as it directly ties to the hypothesis's emphasis on unique catalytic roles.

Why D is correct:

• The lock and key hypothesis defines enzyme specificity, where the active site's shape allows only one substrate to bind and catalyze a single reaction.

Why the others are wrong:

• A: Relates to enzyme composition, not the shape-based binding mechanism.
• B: Describes temperature's impact on enzyme kinetics, unrelated to substrate fit.
• C: Refers to optimal temperature for human enzyme activity, not specificity.

Final answer: D