Question

The efficiency of an enzyme in catalyzing a reaction is due to its capacity:

• A. to form an enzyme - substrate complex
• B. to decrease the bond energies of the substrate molecule
• C. to change the shape of the substrate molecule
• D. none of the above

Answer 1

Answer: (A)

to form an enzyme - substrate complex

A Catalyst is a substance that accelerates the rate of a chemical reaction without undergoing any change in its chemical composition or mass during the reaction. A catalyst accelerates the rate of a reaction by lowering the activation energy.

Enzyme Catalysis - These are catalysts in the living system. Enzymes are substances which by their presence, alter the rate of any biological event. These are mainly proteins, and enzyme action is structure specific.

Enzyme catalysis is the increase in the rate of a chemical reaction by the active site of a protein. The protein catalyst (enzyme) may be part of a multi-subunit complex, and/or may transiently or permanently associate with a co-factor (e.g. adenosine triphosphate). Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalyzed reactions. A key driver of protein evolution is the optimization of such catalytic activities via protein dynamics.

Enzymes are macromolecular biological catalysts. These are highly selective catalysts greatly accelerating both the rate and specificity of metabolic reactions. All enzymes are insoluble since they exist in the colloidal state. Urease is an enzyme that catalyzes the hydrolysis of urea, forming ammonia and carbon dioxide.

They decrease the activation energy by providing an alternate pathway (enzyme reacts with the substrate to form an intermediate ES complex, which would be impossible in the absence of the enzyme) for the process.

Enzyme + Substrate $\to$ Complex $\to$ Product + Enzyme