(a) Explain the importance of enzymes in biological systems. (b) What chemical transformations are catalyzed (i) by the enzyme catalase, \((i i)\) by nitrogenase? (c) Many enzymes follow this generic reaction mechanism, where \(\mathrm{E}\) is enzyme, \(\mathrm{S}\) is substrate, ES is the enzyme-substrate complex (where the substrate is bound to the enzyme's active site), and \(\mathrm{P}\) is the product: 1\. \(\mathrm{E}+\mathrm{S} \rightleftharpoons \mathrm{ES}\) 2\. \(\mathrm{ES} \longrightarrow \mathrm{E}+\mathrm{P}\) What assumptions are made in this model with regard to the rate of the bound substrate being chemically transformed into bound product in the active site?

Enzymes are biological catalysts that accelerate chemical reactions in living organisms without being consumed in the process. They play an essential role in almost every biochemical process that takes place within cells and are crucial for maintaining life. These proteins allow reactions to occur at a faster rate and under milder conditions than would otherwise be necessary, enabling metabolism and other cellular processes to happen efficiently. Some examples of important enzyme functions include breaking down food molecules, repairing damaged cell structures, and helping in the production of energy.

(i) Catalase is an enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2). The chemical transformation can be represented as follows: \[2 H_{2}O_{2} \xrightarrow{Catalase} 2 H_{2}O + O_{2}\] (ii) Nitrogenase is an enzyme that reduces atmospheric nitrogen (N2) to ammonia (NH3) through the process of nitrogen fixation. This reaction is crucial for incorporating nitrogen into molecules essential for life, such as proteins and nucleic acids. The chemical transformation can be represented as follows: \[N_{2} + 8 H^{+} + 8 e^{-} \xrightarrow{Nitrogenase} 2 NH_{3} + H_{2}\]

The given enzyme reaction model describes a simple two-step process involving the formation of an enzyme-substrate complex (ES) and the subsequent generation of products. 1. E + S ↔ ES 2. ES → E + P There are two main assumptions made in this model with regard to the rate of the bound substrate being chemically transformed into bound product in the active site: 1. The model assumes that the initial binding of the enzyme (E) to the substrate (S) to form the enzyme-substrate complex (ES) is reversible. This means the complex can dissociate back into separate enzyme and substrate molecules if the reaction conditions change. 2. The model also assumes that the rate-limiting step is the second step (ES → E + P) where the enzyme-substrate complex is being converted into the product (P) and the free enzyme (E). This implies that the chemical transformation of the substrate into the product within the active site is the slowest step of the overall reaction, which determines the overall reaction rate. This is known as the "steady-state assumption".