CH 3 Smartworks

The free-energy change, ΔG, for the chemical reaction A → B is 0 kJ/mole at 37°C when the concentrations of A and B are 10 M and 0.1 M, respectively. What is the free-energy change for the reaction when the concentrations of A and B are 0.01 M and 1 M, respectively? +23.76 kJ/mole -23.76 kJ/mole +4.61 kJ/mole +11.88 kJ/mole -11.88 kJ/mole

+23.76 kJ/mole

In a chemical reaction, substrate molecule A is broken down to form one molecule of product B and one molecule of product C. The equilibrium constant, K, for this reaction is 0.5. If we start with a mixture containing only substrate A at a concentration of 1 M, what will be the concentration of A when the reaction reaches equilibrium? 0.667 M 0.250 M 0.500 M 0.333 M 0.125 M

0.500 M

For a reaction at 37°C, a 5.94 kJ/mole decrease in ΔG changes K by a factor of which of the following? 10^2 10^3 10^-1 10^1

10^1

Which statement is true about the removal of a terminal phosphate from ATP? A. The reaction is energetically favorable. B. The reaction is a condensation reaction. C. The reaction is associated with a positive change in ΔG°.

A. The reaction is energetically favorable.

What is the relationship between /delta G and /delta G0?Choose one: A. /delta G0 is the free-energy change at standard temperature. B. /delta G0 is the free-energy change at standard temperature and concentrations. C. /delta G0 is the free-energy change at standard concentrations. D. /delta G0 is the free-energy change at standard pressure.

B. /delta G0 is the free-energy change at standard temperature and concentrations.

The ΔG° of the hydrolysis reaction of ATP is -7.3 kcal/mole, but in a cell the actual ΔG is much more negative. What is the reason for the ΔG° and ΔG difference? A. The concentration of ATP is much lower than the concentrations of its hydrolysis products, ADP and Pi. B. ATP is much higher in concentration than the products ADP and Pi. C. Cells use enzymes to perform these reactions, resulting in a difference between ΔG° and ΔG. D. None of the above address the ΔG° and the cellular ΔG difference.

B. ATP is much higher in concentration than the products ADP and Pi.

A reaction A → B has a negative ΔG under experimental conditions. Which statement is true about this reaction? A. The formation of product B will decrease the entropy of the universe. B. Increasing the concentration of B will increase the ΔG, making it less negative. C. The reaction cannot proceed until it is coupled to a reaction with a positive ΔG. D. The reaction is energetically unfavorable. E. The reaction will proceed spontaneously and rapidly.

B. Increasing the concentration of B will increase the ΔG, making it less negative.

Your company has developed an organic molecule with commercial potential and you know how to produce it in the lab. You want to increase production and make as much of the molecule as possible, but the reaction has a positive ΔG°. What can you do to try to drive the reaction toward your desired product? Choose one or more: A.add an enzyme that does not couple to another reaction B.increase the concentration of reactants C.add some products initially to get the reaction primed D.continually remove products

B.increase the concentration of reactants D.continually remove products

Which is not true of a chemical reaction at equilibrium?Choose one: The rates of the forward and reverse reactions are equal. Both the forward and reverse reactions have stopped. ΔG is equal to zero. The net concentrations of substrate and product do not change.

Both the forward and reverse reactions have stopped.

Chemical reactions proceed spontaneously only in which direction?Choose one: A. one that leads to an increase in orderliness B. one that releases water C. one that leads to a release of free energy D. one that goes "uphill" E. one that is energetically unfavorable

C. one that leads to a release of free energy

In the first reaction of glycolysis (the pathway that begins the oxidative breakdown of sugars), the enzyme hexokinase uses ATP to catalyze the phosphorylation of glucose to glucose 6-phosphate and ADP. The ΔG° of this reaction is a favorable -4.06 kcal/mole.Another sometimes active enzyme, called glucose 6-phosphatase, effectively "reverses" this reaction, hydrolyzing glucose 6-phosphate back to glucose and releasing a phosphate. The ΔG° of this reaction is -3.34 kcal/mole.Based on these values, what is the ΔG° for the hydrolysis of ATP: ATP + H2O → ADP + Pi?Choose one: A. -0.72 kcal/mole B. +0.72 kcal/mole C. +14.8 kcal/mole D. -7.4 kcal/mole E. +7.4 kcal/mole

D. -7.4 kcal/mole

What is the value of /delta G at equilibrium?Choose one: A. It depends on the concentration of substrates and products. B. negative C. positive D. zero

D. zero

In the second step of glycolysis (the pathway that begins the oxidative breakdown of sugars), the enzyme phosphoglucose isomerase converts glucose 6-phosphate to fructose 6-phosphate. The equilibrium constant, K, for this reaction is 0.36. If ΔG° = -5.94 ×× log K, which conclusion can be made about this reaction? A. The ΔG° is negative, but whether the reaction proceeds will depend on ΔG, not ΔG°. B. The ΔG° is negative, so the reaction must be coupled to the hydrolysis of ATP. C. The ΔG° is positive, so the reaction will proceed in the reverse direction. D. The ΔG° is negative, so the reaction will always proceed in the forward direction. E. The ΔG° is positive, but in a cell that is burning sugars, the reaction can still proceed in the forward direction.

E. The ΔG° is positive, but in a cell that is burning sugars, the reaction can still proceed in the forward direction.

Determine whether the following statement is true or false: The formation of ATP can be coupled to energetically unfavorable reactions to allow them to proceed.

False

Consider the reaction A + B → AB. How is the equilibrium constant expressed for this reaction with two substrates and a single product?Choose one: K = [AB] / [A][B] K = ([A] + [B]) / [AB] K = [AB] / ([A] + [B]) K = [A][B] / [AB]

K = [AB] / [A][B]

Determine whether the following statement is true or false: Energetically unfavorable reactions can occur if they are coupled to a second reaction with a negative ΔG so large that the net ΔG of the entire process is negative.

True

Determine whether the following statement is true or false: The free-energy change (ΔG) and the standard free-energy change (ΔG°) of a reaction differ in that ΔG depends on the concentrations of the molecules in the reaction, whereas for ΔG°, these concentrations are set to fixed values.

True

Determine whether the following statement is true or false: The mass of the living cell cannot be greater than the amount of matter that is absorbed by the cell.

True

Determine whether the following statement is true or false: The overall free-energy change for coupled reactions is equal to the sum of the free-energy changes for each individual reaction.

True

For the simple reaction Y → X, the equilibrium constant K is equal to which of the following equations? [Y] × [X] [X] × [Y] [X] / [Y] [Y] / [X]

[X] / [Y]

A reaction occurs spontaneously only if the change in free energy (ΔG) is

negative

Which reaction can be driven by the hydrolysis of a molecule of ATP? glucose + oxygen → CO2 + water (ΔG = -686 kcal/mole) sucrose → glucose + fructose (ΔG = -5.5 kcal/mole) CO2 + water → glucose + oxygen (ΔG = 686 kcal/mole) glucose + fructose → sucrose (ΔG = 5.5 kcal/mole)

glucose + fructose → sucrose (ΔG = 5.5 kcal/mole)