What causes competitive inhibition?all substrate is removed from the cellthe active site becomes blocked by a competing moleculethe enzyme is broken in half by lysosomes

Competitive inhibition is caused when the active site of an enzyme becomes blocked by a competing molecule. Here's a step-by-step explanation:

1. Enzymes are proteins that speed up chemical reactions in a cell. They have a region called the active site where substrates (the molecules enzymes act upon) bind.

2. In competitive inhibition, a molecule similar to the substrate binds to the active site of the enzyme. This molecule is known as a competitive inhibitor.

3. The competitive inhibitor competes with the substrate for the same active site, blocking the substrate from binding.

4. When the inhibitor is bound to the active site, the enzyme can't catalyze the reaction with its substrate. This decreases the rate of the reaction.

5. The inhibition can be overcome by increasing the concentration of the substrate. With more substrate molecules present, it's more likely that a substrate molecule (rather than an inhibitor molecule) will bind to the active site.

So, competitive inhibition is caused by a competing molecule that blocks the active site of an enzyme, preventing the substrate from binding and the reaction from occurring.