AP Lovrien - Enzymes And Energy

According to the induced fit hypothesis of enzyme catalysis, the correct statement is that the binding of the substrate changes the shape of the enzyme's active site. This hypothesis proposes that the active site of an enzyme is not a rigid structure, but rather it can undergo conformational changes upon substrate binding. The enzyme's active site can adjust its shape to better accommodate and interact with the substrate, leading to a more efficient catalytic reaction. This concept highlights the dynamic nature of enzyme-substrate interactions and the importance of the induced fit in enzyme catalysis.

Anabolic pathways involve the synthesis of complex molecules from simpler ones, such as building polymers from monomers. This process requires energy input, usually in the form of ATP, to drive the chemical reactions and build up larger molecules. Enzymes play a crucial role in facilitating these reactions, but they are not mentioned as being independent of enzymes in the question. Therefore, the correct answer is that anabolic pathways consume energy to build up polymers from monomers.

Enzymes increase the rate of chemical reactions by lowering activation energy barriers. Activation energy is the energy required to start a chemical reaction. Enzymes act as catalysts, facilitating the reaction by reducing the amount of energy needed to initiate it. They achieve this by binding to the reactant molecules and bringing them closer together, allowing them to interact more easily and forming a transition state with lower energy requirements. This lowers the activation energy barrier, making the reaction proceed faster. Therefore, enzymes play a crucial role in accelerating biochemical reactions in living organisms.

The active site of an enzyme is the region that is involved in the catalytic reaction of the enzyme. This means that it is the specific location where the enzyme binds to its substrate and facilitates the conversion of the substrate into a product. The active site provides a precise environment for the reaction to occur, including the necessary amino acid residues and functional groups that participate in the catalysis. It is at the active site that the enzyme and substrate interact and form an enzyme-substrate complex, allowing the reaction to proceed efficiently.

An endergonic reaction is a chemical reaction that requires an input of energy in order to proceed. In this type of reaction, the Gibbs free energy (G) increases, indicating that the products have a higher energy state than the reactants. This means that the reaction is not spontaneous and will not occur without the addition of energy. Therefore, the correct answer is endergonic.

When glucose monomers are joined together to form a cellulose polymer, the process requires energy and is not spontaneous, resulting in a positive change in Gibbs free energy (+ change in G). Additionally, the formation of the glycosidic linkages involves bond formation, which requires energy, leading to a positive change in enthalpy (+ change in H). However, the formation of a polymer from monomers typically results in a decrease in disorder, leading to a negative change in entropy (- change in S). Therefore, the correct answer is + change in G, + change in H, - change in S.

Malonic acid is used in this experiment as a competitive inhibitor. This means that it competes with succinate for the active site of succinate dehydrogenase. By binding to the active site, malonic acid prevents succinate from binding and inhibits the conversion of succinate to fumarate. The fact that malonic acid resembles succinate but cannot be acted upon by succinate dehydrogenase allows it to effectively compete with succinate for the enzyme's active site. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid, indicating its competitive nature.

Whenever energy is transformed, there is always an increase in the entropy of the universe. This is because the second law of thermodynamics states that in any energy transformation, the total entropy of the system and its surroundings will always increase. Entropy is a measure of the disorder or randomness in a system, and energy transformations tend to increase the overall disorder of the universe. Therefore, the correct answer is entropy of the universe.

If the ΔG of the enzyme-catalyzed reaction is -20 kcal/mol, it means that the reaction is exergonic and releases energy. Doubling the amount of enzyme in the reaction does not affect the ΔG value, as it is a measure of the energy difference between the reactants and products. Therefore, the ΔG for the new reaction will still be -20 kcal/mol.

The given information states that succinate dehydrogenase catalyzes the conversion of succinate to fumarate. This implies that succinate is the substrate, as it is the molecule being acted upon by the enzyme, and fumarate is the product, as it is the molecule formed as a result of the reaction.

Dehydration reactions involve the removal of water molecules to form larger molecules. This process leads to a decrease in the number of possible arrangements of molecules, resulting in a decrease in entropy within a cell. As a result, dehydration reactions would decrease the entropy within a cell.

An increase in a cell's catabolic activity is likely to lead to an increase in the concentration of ATP in a cell. Catabolic activity involves the breakdown of molecules, such as glucose, to release energy. This energy is used to synthesize ATP through cellular respiration. Therefore, an increase in catabolic activity would result in more molecules being broken down, leading to a higher production of ATP.