Optimal pH for stomach protease activity

Steps:

• Stomach proteases like pepsin function in acidic conditions of the stomach.
• Pepsin's activity peaks at low pH (around 2) due to the stomach's HCl environment.
• Examine diagrams for enzyme activity versus pH, identifying the curve with maximum rate at acidic pH.
• Match the diagram showing highest activity below pH 3 and low activity at neutral or basic pH.

Why C is correct:

• Diagram C displays peak activity at pH 2, aligning with pepsin's optimal function in acidic gastric conditions as defined by enzyme-substrate interactions stabilized at low pH.

Why the others are wrong:

• A shows peak at pH 7, typical for neutral pH enzymes like pancreatic proteases.
• B shows peak at pH 9, suited for alkaline environments, not stomach.
• D shows flat or broad activity across pH, ignoring pH specificity of pepsin.

Final answer: C