What is the threshold effect in allosteric enzymes and how does it affect their sensitivity to substrate concentration?

• A. Below a certain substrate concentration, allosteric enzymes show little activity, but become highly sensitive once the threshold is reached.
• B. Allosteric enzymes are always sensitive to substrate concentration changes.
• C. Allosteric enzymes show constant activity regardless of substrate concentration.
• D. Allosteric enzymes are insensitive to substrate concentration changes.

Answer: (A)