Final answer:
The best description of an individual enzyme is that it lowers the activation energy of a reaction and affects only very specific reactions. Enzymes are highly specific biological catalysts that help accelerate reactions without being consumed in the process.
Step-by-step explanation:
The statement that BEST describes an individual enzyme is: C. it lowers the activation energy of a reaction and affects only very specific reactions. Enzymes are biological catalysts that accelerate biochemical reactions by lowering the activation energy required for the reaction to occur. This means that they reduce the energy needed for reactants, known as substrates, to react with each other. Enzymes are highly specific; they only bind to particular substrates at their active site and facilitate very specific chemical reactions without being consumed in the process.
One of the key functions of an enzyme is to form an enzyme-substrate complex that can lower the activation energy by contorting the substrate molecules in a way that facilitates bond-breaking, helping reach the transition state. This process may involve the enzyme temporarily forming covalent bonds with the substrate. It is important to note that the enzyme will return to its original state after the reaction, ready to catalyze another reaction.