Final answer:
The acronym "ea" refers to enzyme activity, and the correct answer is option A, which states that enzymes are proteins facilitating chemical reactions by lowering activation energy, thereby helping organisms accomplish metabolic requirements.
Step-by-step explanation:
The term "ea" in the context of the question stands for enzyme activity, and the correct option from the provided list would be A) "ea" stands for enzyme activity, and enzymes are proteins that facilitate chemical reactions by lowering activation energy barriers. Enzymes play a crucial role in assisting living organisms to accomplish their metabolic requirements by acting as biological catalysts. These protein molecules speed up the multitude of chemical reactions required for life. They lower the activation energy required for reactions, facilitating the transformation of substrates into products.
Enzymes have an active site specifically designed to bind to their corresponding substrates, which are the reactant molecules enzymes act upon. When the enzyme and substrate form an enzyme-substrate complex, the enzyme may distort the shape of the substrate to weaken bonds that need to be broken or form new ones. Some enzymes can also actively participate in the chemical reaction, forming transient covalent bonds with the substrate. In all cases, the enzyme emerges unchanged after facilitating the reaction, ready to assist another substrate molecule. Their ability to lower activation energy and speed up reactions without being consumed or altered makes enzymes essential for the functioning of all living cells.