14. An is a protein that increases the rate of a chemical reaction by the amount of energy required to start the chemical reaction.

16. The compounds created during a chemical reaction are known as the .

17. The surface of an enzyme where the substrate binds to the enzyme is known as the .

19. The characteristic of the cell membrane that allows it to regulate what enters and leaves the cell is known as .

Answers and Explanations:

14. Catalysts; decreasing; activation.

In science, catalysts are known to speed up a reaction. Every reaction starts with activation energy, but the smaller the activation energy, the faster the reaction will run. That's why catalysts decrease that energy.

16. Products

Chemical reactions turn reactants into products.

17. Active site

The substrate binds to the enzyme at an place called the active site, where the shape of the site matches the shape of the substrate. Usually this model can be called the lock-and-key model, or more recently, the induced fit model.

19. Semi-permeability

Semi-permeability basically means that only certain things can enter the cell. For example, nutrients can come in while waste can be let out. However, harmful substances will be recognized by the cell, so they can't come in thanks to the semi-permeable membrane.

Hope this helps!