Enzyme Activity & Redox Reactions PDF

# Enzyme Activity ## Introduction When the chemical reaction between an enzyme and a substrate is complete, the enzyme remains the same and is ready to do another reaction while the substrate is changed into a product. ## Models of Enzyme Activity There are two models to explain enzyme activity...

# Enzyme Activity ## Introduction When the chemical reaction between an enzyme and a substrate is complete, the enzyme remains the same and is ready to do another reaction while the substrate is changed into a product. ## Models of Enzyme Activity There are two models to explain enzyme activity: - **Lock and Key Hypothesis:** The substrate fits exactly to the active site of the enzyme like a jigsaw puzzle. - **Induced Fit Model:** The shape of the enzyme changes when the substrate fits into the active site. ## Naming Enzymes Enzyme names usually end in "ase" and are named after the affected substrate, e.g., proteases for proteins, lipases for lipids, amylases for starch. ### Types of Enzymes | Enzyme Type | Substrate | Examples | |---|---|---| | Proteolytic Enzymes (Protease) | Meat, seafood, soybean, etc | - | | Fats-Degrading Enzyme (Lipase) | Beef, foie gras and fresh cream, egg yolk, cheese, etc | - | | Sugar-Degrading Enzyme (Amylase) | Chocolate, cake, biscuits, cookies, soft drinks, alcohol | - | ## Enzyme Specificity Enzymes are highly specific for a reaction and only catalyze substrates which can fit inside its active site. Only correctly sized substrates will fit perfectly into the enzyme and cause a reaction. ## Practical Applications of Enzymes Enzymes are all around us and even within us. Here are some of their practical applications in daily life: - **Detergents:** Proteases (remove blood stains), amylases (remove starchy stains), or lipases (remove oil or makeup stains). - **Digestive System:** Salivary amylase breaks down starches into simple sugars. Once food reaches the stomach, digestive enzymes continuously break down large molecules into smaller forms to facilitate fast absorption of nutrients in the body. ## Factors Affecting Enzyme Activity **1. pH (Acidity and Basicity):** - pH is a measure of the hydrogen ion (H+) and hydroxide ion (OH-) concentrations. It ranges from pH1 to pH14. - Acid solutions have pH values below 7, while basic solutions (alkalis are bases) have pH values above 7. - Different enzymes have different optimum pH values. Any change in pH above or below the optimum will quickly cause a decrease in the rate of reaction. - Extreme changes in pH can cause denaturation of enzymes, permanently losing their function. - For example, most human enzymes = pH 6-8, pepsin (stomach) = pH 2-3, and trypsin (small intestines) = pH 8. **2. Temperature:** - Increasing temperature increases the rate of reaction. - Random collision of enzymes with substrate molecules results to more products. - There is a certain temperature at which an enzyme's catalytic activity is at its greatest (optimum temperature). Different enzymes function in different organisms in different environments. - For the enzymes in the human body cells, the optimum temperature is 37°C. Above this temperature, the enzyme structure begins to denature (breaking of weaker bonds). - What happens to an egg (mostly protein) as you cook it? The egg proteins denature from heat. - What happens to your hair (protein) when you use a curling iron? The hair proteins denature from heat. **3. Substrate:** - Increasing substrate concentration increases the rate of reaction. - More substrate molecules will be colliding with enzyme molecules and, thus, more products will be formed. - However, any increase in concentration will have no effect on the rate of reaction since substrate concentration will no longer be the limiting factor. - Enzymes will become saturated and will be working at their maximum possible rate. ## Oxidation and Reduction - The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. - The transfer of energy in the form of electrons allows the cell to transfer and use energy incrementally, that is, in small packages rather than a single, destructive burst. - Reactions that remove electrons from donor molecules, leaving them oxidized, are oxidation reactions; those that add electrons to acceptor molecules, leaving them reduced, are reduction reactions. - Because electrons can move from one molecule to another, oxidation and reduction occur in tandem. They are complementary processes which occur together. Thus, these reactions are now called oxidation-reduction reactions or redox reactions. - The more general definition of oxidation is the loss of electrons and of reduction, the gain of electrons. ### Redox Enzymes - Redox enzymes are a general term for enzymes that catalyze the redox between two molecules. - Among them, oxidase can catalyze the oxidation of substances by oxygen, and dehydrogenase can catalyze the removal of hydrogen from material molecules. - Numerous redox enzymes in organisms require coenzyme NAD or NADP as well as FAD or FMN when reacting. - Some enzymes do not require a coenzyme or a prosthetic group, and directly use oxygen as a carrier of electrons, such as glucose oxidase. - The process of redox reaction in a living body has a movement of a pair of hydrogen atoms, the transfer of electrons, or an oxygen atom addition. - A substance giving electrons or H to oxidize is called an electron donor or a hydrogen donor. - A substance that acts as an oxidant and accepts electrons or hydrogen and is itself reduced is called an electron acceptor or a hydrogen acceptor. ## Conclusion Enzymes play a crucial role in many vital biochemical reactions within our bodies. Understanding how they function and the factors that influence their activity is essential in many fields, including medicine, biotechnology, and food science.