Campbell 8.4 - 8.5 Quiz

The correct answer is sucrase because the question mentions that the diagram shows the hydrolysis of sucrose. Sucrase is the enzyme responsible for breaking down sucrose into its component sugars, glucose, and fructose. Therefore, it is logical to assume that the enzyme shown in the diagram is sucrase.

The reaction profile in Fig. 8.12 must be an exergonic reaction since it has a negative deltaG. In exergonic reactions, the products have lower energy than the reactants, and energy is released during the reaction. A negative deltaG indicates that the reaction is spontaneous and can occur without the input of external energy. Therefore, the given reaction profile fits the characteristics of an exergonic reaction.

The correct answer for this question is "energy of activation" or "activation energy" or "Ea" or "free energy of activation". These terms all refer to the energy required to initiate a reaction. It represents the minimum energy that reactant molecules must possess in order to undergo a chemical reaction. The activation energy determines the rate at which a reaction occurs, as higher activation energies result in slower reactions.

Enzymes are highly specific to their substrates because of their precise 3-D shapes. The active site of an enzyme is shaped in a way that only certain molecules, known as substrates, can fit into it. Even molecules that are very similar to the substrate will not be able to bind to the enzyme and undergo a reaction. This specificity ensures that enzymes only catalyze specific reactions and prevents unwanted side reactions from occurring.

Enzymes have an optimal temperature and pH at which their 3D shape is most perfect. This means that the enzyme is able to function at its highest efficiency and catalyze reactions effectively. Any deviation from the optimal temperature or pH can cause changes in the enzyme's shape, leading to a decrease in its activity. Therefore, maintaining the optimal conditions is crucial for the enzyme to work at its best.

The active site is the specific location on an enzyme where a substrate molecule binds. It is a highly precise and complementary fit, similar to a lock and key mechanism. The active site provides the necessary chemical environment for the substrate to undergo a reaction, leading to the formation of a product. Enzymes are highly specific, and their active sites determine which substrates they can bind to and catalyze reactions with. In some cases, enzymes may have multiple active sites, allowing them to bind to and catalyze reactions with multiple substrates simultaneously.

An inhibitor is a substance that binds to an enzyme and reduces its ability to function. It acts as the opposite of a cofactor, which enhances the enzyme's activity. By binding to the enzyme, inhibitors can block the active site or alter the enzyme's conformation, preventing it from catalyzing the reaction efficiently. Inhibitors are commonly used in medical treatments to regulate enzyme activity and inhibit specific biochemical pathways.

Competitive inhibitors are a type of enzyme inhibitor that bind to the active site of the enzyme. This binding prevents the substrate from binding to the enzyme, as the inhibitor molecule competes with the substrate for the active site. As a result, the enzyme-substrate complex cannot form, and the reaction is inhibited.

Cofactors are molecules that can bind to enzymes and assist in their functioning. They can be inorganic ions or organic molecules, such as vitamins. By binding to enzymes, cofactors can alter their shape or provide necessary chemical groups for catalytic reactions to occur. In this context, both "cofactor" and "cofactors" are correct as they refer to the singular and plural forms of the term. Similarly, "coenzyme" and "coenzymes" are also correct as they denote specific types of organic cofactors that are required for enzyme activity.

Raising the temperature of an enzyme-catalyzed reaction increases the kinetic energy of the molecules, causing them to move around more. This increased movement leads to a higher frequency of collisions between enzymes and substrates. Since enzymes catalyze reactions by binding to substrates, more collisions between enzymes and substrates means more opportunities for the reaction to occur. Therefore, increasing the temperature initially speeds up the reaction rate.

The correct answer is 40 degrees Celsius. This means that there is a 40-degree difference between the optimal temperature of a typical human enzyme and that of a thermophilic bacteria. Thermophilic bacteria are able to thrive in high-temperature environments, while human enzymes have an optimal temperature range that is lower.

The given statement is true because it states that molecule C-D is a reactant of the reaction shown in Fig. 8.12. This implies that molecule C-D is involved in the chemical reaction and is consumed during the process. Therefore, the answer is true.

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction to occur. They do not affect the overall thermodynamics of the reaction, meaning they cannot change the free energy change (deltaG) of a reaction. Enzymes only facilitate reactions that are energetically favorable and would occur anyway, but they do not alter the equilibrium or the final outcome of the reaction. Therefore, the statement that enzymes cannot change the deltaG of a reaction is true.

Noncompetitive inhibitors do not bind in the active site of the enzyme. Instead, they bind to another site on the enzyme, causing a change in its 3D shape. This change in shape prevents the substrate from binding to the active site, inhibiting the enzyme's activity. Both "noncompetitive inhibitor" and "non-competitive inhibitor" refer to the same concept.

The size of the activation energy is directly related to the rate of a reaction. A higher activation energy means that more energy is required for the reaction to occur, resulting in a slower reaction rate. Conversely, a lower activation energy means that less energy is needed, leading to a faster reaction rate. Therefore, the statement is true.

The given statement is false. Pepsin works best at acidic pHs, not basic pHs. Pepsin is an enzyme that breaks down proteins in the stomach, and it functions optimally in the highly acidic environment of the stomach. On the other hand, trypsin is an enzyme that works best at basic pHs, specifically in the small intestine where the pH is more alkaline.

The activation energy (Ea) is the energy required for a reaction to occur. Enzymes lower the activation energy, making it easier for the reaction to proceed. As a result, the rate of reaction increases when an enzyme is present. The reactants and products of the reaction remain the same regardless of the presence of an enzyme. The deltaG (free energy change) also remains unchanged as enzymes do not affect the overall energy change of a reaction.

When the temperature of a reaction gets too hot, the increased energy can disrupt the weak hydrogen bonds, van der Waals interactions, and even the stronger ionic bonds. Hydrogen bonds are easily broken due to their relatively low strength, while van der Waals interactions, which are weak attractive forces between molecules, can also be disrupted. Additionally, high temperatures can provide enough energy to overcome the strong electrostatic forces holding ions together in ionic bonds, causing them to break. Covalent bonds, on the other hand, are much stronger and require significantly higher temperatures to be disrupted.