Bio Chapter 8

Which of the following statements about allosteric proteins is/are true?

All of the first three listed responses are correct.

Which of the following statements about enzymes is incorrect?

An enzyme is consumed during the reaction it catalyzes.

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Which of the following states the relevance of the first law of thermodynamics to biology?

Energy can be freely transformed among different forms as long as the total energy is conserved.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?

Energy input into the organism must be occurring to drive the decrease in entropy.

Which of the following statements about enzyme function is correct?

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Which of the following statements about enzymes is true?

Enzymes speed up the rate of the reaction without changing the DG for the reaction.

Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true?

High levels of ADP act as an allosteric activator of catabolic pathways

When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations?

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?

Neither the sign nor the magnitude of ΔG have anything to do with the speed of a reaction.

Which of the following environments or actions would not affect the rate of an enzyme reaction?

None of the listed responses is correct.

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Organisms acquire energy from, and lose energy to, their surroundings.

Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation?

Succinylcholine must be a competitive inhibitor with acetylcholine.

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible.

Which of the following statements about the active site of an enzyme is correct?

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

According to the second law of thermodynamics, which of the following is true?

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

What is meant by the "induced fit" of an enzyme?

The enzyme changes its shape slightly as the substrate binds to it.

Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions?

The first and second listed responses are correct.

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?

The first and second listed responses are correct.

From the equation ΔG = ΔH - TΔS it is clear that _____.

The first three choices are correct.

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

Molecules A and B contain 110 kcal/mol of free energy and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.

Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell against the ion's concentration gradient?

This is an example of energy coupling.

Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?

To obey the first law, the crops must represent an open system.

Which of the following has the most free energy per molecule?

a starch molecule

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of _____.

allosteric regulation

How do enzymes lower activation energy?

by locally concentrating the reactants

Which is the most abundant form of energy in a cell?

chemical energy

Which of the following reactions would be endergonic?

glucose + fructose → sucrose

Enzyme activity is affected by pH because _____.

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

The electronic arrangement in which of the following molecules means that this molecule has/have greater free energy than the others?

methane

Which of the following is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP, involved in the production of electrochemical gradients?

proton movement against a gradient of protons

An exergonic (spontaneous) reaction is a chemical reaction that _____.

releases energy when proceeding in the forward direction

In general, the hydrolysis of ATP drives cellular work by _____.

releasing free energy that can be coupled to other reactions

Which of the following is changed by the presence of an enzyme in a reaction?

the activation energy

Which of the following situations does not represent an energy transformation?

the coupling of ATP hydrolysis to the production of a proton gradient across a membrane by a proton pump

Which of the following statements correctly describe(s) the role(s) of heat in biological reactions?

the first and second choices are correct

Which of the following determines the sign of ΔG for a reaction?

the free energy of the reactants and the free energy of the products

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?

the hydrolysis of ATP

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because _____.

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP

A chemical reaction is designated as exergonic rather than endergonic when _____.

the potential energy of the products is less than the potential energy of the reactants

A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that _____.

there is too little activation energy available

Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous?

ΔG

If, during a process, the system becomes more ordered, then _____.

ΔS is negative

When one molecule is broken down into six component molecules, which of the following will always be true?

ΔS is positive