A drug molecule has been designed to inhibit the activity of an enzyme - VCE - SSCE Biology - Question 1 - 2013 - Paper 1

To determine the most likely shape for the drug molecule that can competitively inhibit the enzyme, we need to understand that competitive inhibition occurs when a molecule resembles the substrate of the enzyme and competes for binding at the active site.

In this case, upon examining the given options A, B, C, and D, we must look for the shape that best fits the active site of the enzyme shown. The correct shape will have similar dimensions and features that allow it to occupy the active site without undergoing a chemical reaction.

Upon reviewing the options, option B best mimics the size and contour required for effective binding. It can be seen that option B has a shape that closely resembles the active site, allowing it to fit perfectly and inhibit the enzyme's activity by preventing the actual substrate from binding. Therefore, option B is the correct answer.