Exam 3: Energy, Catalysis, and Biosynthesis

In the case of a simple conversion reaction such as X→Y, which value of ΔG° is associated with a larger concentration of X than Y at equilibrium? (Hint: How is ΔG° related to K?)

You are studying a biochemical pathway that requires ATP as an energy source.To your dismay, the reactions soon stop, partly because the ATP is rapidly used up and partly because an excess of ADP builds up and inhibits the enzymes involved.You are about to give up when the following table from a biochemistry textbook catches your eye. $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text {hydrolysis}$ $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\underline{\text {reaction}}$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$ $\Delta G^{\circ}$ $\text { creatine + ATP } \quad\quad\quad\quad \stackrel{\text { enzyme A }}{\longrightarrow} \text { creatine phosphate + ADP +3 kcal/mole }$ $\text { ATP }+\mathrm{H}_{2} \mathrm{O} \quad\quad\quad\quad\quad \stackrel{\text { enzyme B }}{\longrightarrow} \mathrm{ADP}+\text { phosphate } \quad \quad\quad\quad-7.3 \mathrm{kcal} / \text { mole }$ $\text { pyrophosphate }+\mathrm{H}_{2} \mathrm{O} \quad \stackrel{\text { enzyme } \mathrm{C}}{\longrightarrow} 2 \text { phosphate } \quad\quad\quad\quad \quad\quad\quad\quad-7 \mathrm{kcal} / \text { mole }$ glucose 6-phosphate $+\mathrm{H}_{2} \mathrm{O} \quad\stackrel{\text { enzyme D }}{\longrightarrow}$ qlucose + phosphate $\quad\quad\quad\quad\quad\quad\quad-3.3 \mathrm{kcal} / \mathrm{mole}$ Table 3-43 Which of the following reagents is/are most likely to revitalize your reaction?

At first glance, it may seem that living systems are able to defy the second law of thermodynamics.However, on closer examination, it becomes clear that although cells create organization from raw materials in the environment, they also contribute to disorder in the environment by releasing

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB.Which of the following is the correct way to calculate the equilibrium constant for the association between A and B?

Coenzyme A can be converted to acetyl CoA, which is an important activated carrier molecule that has a central role in metabolism and can be used to add two carbons in each successive cycle of fatty acid synthesis. A.Identify the location and type of high-energy bond in the acetyl CoA molecule shown in Figure 3-77. B.How does the bond energy help promote the synthesis of fatty acids? C.What function does the rest of the coenzyme A molecule serve in these reaction pathways? Figure 3-77

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell.Their energy is stored in a readily transferable form such as high-energy electrons or chemical groups.Which of the molecules below donates a chemical group rather than electrons?

The second law of thermodynamics states that the disorder in any system is always increasing.In simple terms, you can think about dropping NaCl crystals into a glass of water.The solvation and diffusion of ions is favored because there is an increase in

The equilibrium constant (K) for the reaction Y→X can be expressed with respect to the concentrations of the reactant and product molecules.Which of the expressions below shows the correct relationship between K, [Y], and [X]?

Two college roommates do not agree on the best way to handle the clutter piled up in your dorm room.Roommate 1 explains that chaos is inevitable, so why fight it? Roommate 2 counters that maintaining an organized environment makes life easier in many ways, and that chaos is not inevitable.What law of thermodynamics drives the thinking of Roommate 1? What thermodynamic argument can be used to support Roommate 2?

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is

The study of enzymes also includes an examination of how the activity is regulated.Molecules that can act as competitive inhibitors for a specific reaction are often similar in shape and size to the enzyme's substrate.Which variable or variables used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor?

Consider an analogy between reaction-coupling and money.In a simple economy, barter provides a means of direct exchange of material goods.For example, the owner of a cow may have excess milk and need eggs, whereas a chicken owner has excess eggs and needs milk.Provided that these two people are in close proximity and can communicate, they may exchange or barter eggs for milk.But in a more complex economy, money serves as a mediator for the exchanges of goods or services.For instance, the cow owner with excess milk may not need other goods until three months from now, or may want goods from someone who does not need milk.In this case, the "energy" from providing milk to the economy can be temporarily "stored" as money, which is a form of "energy" used for many transactions in the economy.Using barter and money as analogies, describe two mechanisms that can serve to drive an unfavorable chemical reaction in the cell.

What information regarding an enzyme-catalyzed reaction is obtained in a plot of the inverse of the initial velocities against the inverse of the corresponding substrate concentrations?

The maximum velocity (V_max) of an enzymatic reaction is an important piece of information regarding how the enzyme works.What series of measurements can be taken in order to infer the maximum velocity of an enzyme-catalyzed reaction?

The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of

Catalysts are molecules that lower the activation energy for a given reaction.Cells produce their own catalysts, called

The small molecule cyclic AMP (cAMP) takes about 0.2 second to diffuse 10 μm, on average, in a cell.Suppose that cAMP is produced near the plasma membrane on one end of the cell; how long will it take for this cAMP to diffuse through the cytosol and reach the opposite end of a very large cell, on average? Assume that the cell is 200 μm in diameter.