ap bio chapter eight test bank

Which of the following is a statement of the first law of thermodynamics?

A) Energy cannot be created or destroyed.

Experiment - What is the purpose of using malonic acid in this experiment?

A) It is a competitive inhibitor.

Which of the following statements is (are) true about enzyme-catalyzed reactions?

A) The reaction is faster than the same reaction in the absence of the enzyme.

SQ - If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

A) add more of the enzyme.

Which of the following is considered an open system?

A) an organism

Which of the following types of reactions would decrease the entropy within a cell?

A) dehydration reactions

A chemical reaction that has a positive △G is correctly described as

A) endergonic.

The organization of organisms has become increasingly complex with time. This statement

A) is consistent with the second law of thermodynamics.

Figure 8.2 - Which of the following bests describes the reaction?

A) negative △G, spontaneous

Competitive inhibitors block the entry of substrate into the active site of an enzyme. On which of the following properties of an active site does this primarily depend?

A) the ability of an enzyme to form a template for holding and joining molecules

Among enzymes, kinases catalyze phosphorylation, while phosphatases catalyze removal of phosphate(s). A cell's use of these enzymes can therefore function as an on-off switch for various processes. Which of the following is probably involved?

A) the change in a protein's charge leading to a conformational change

When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows:

B) +△G, +△H, -△S

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a △G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the △G for the new reaction?

B) -20 kcal/mol

SQ - Which of the following metabolic processes can occur without a net influx of energy from some other process?

B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

Which of the following statements regarding enzymes is true?

B) Enzymes increase the rate of a reaction.

Why is ATP an important molecule in metabolism?

B) It provides energy coupling between exergonic and endergonic reactions.

In order to attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur in order for the final attachment to occur?

B) The binding of the first two molecules must cause a 3-dimensional change that opens another active site on the enzyme.

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

B) The organism ultimately must obtain all of the necessary energy for life from its environment.

Which of the following is true for all exergonic reactions?

B) The reaction proceeds with a net release of free energy

Which of the following statements is true concerning catabolic pathways?

B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

B) activation energy.

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. Substance A functions as

B) an allosteric inhibitor.

Which of the following is likely to lead to an increase in the concentration of ATP in a cell?

B) an increase in a cell's catabolic activity

Which of the following represents the activation energy required for the enzyme-catalyzed reaction?

B) b

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

B) by changing the shape of a reactant

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

B) compartmentalization of enzymes into defined organelles

Figure 8.2 - Which of the following terms best describes the reaction?

B) exergonic

SQ - Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________.

B) exergonic; endergonic

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as

B) feedback inhibition.

The active site of an enzyme is the region that

B) is involved in the catalytic reaction of the enzyme.

Which of the following best describes enthalpy (H)?

B) the heat content of a chemical system

Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein?

C) +△H, -△S, +△G

Which of the following statements describes enzyme cooperativity?

C) A substrate molecule bound to an active site affects the active site of several subunits.

A number of systems for pumping across membranes are powered by ATP. Such ATP- powered pumps are often called ATPases although they don't often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a muscle cell cytosol has a free calcium ion concentration of 10 -7 in a resting cell, while the concentration in the SR can be 10 -2, then how is the ATPase acting?

C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.

SQ - Using a series of arrows, draw the branched metabolic reaction pathway described by the following statements, then answer the question at the end. ∙ L can form either M or N. ∙ M can form O. ∙ O can form either P or R. ∙ P can form Q. ∙ R can form S. ∙ O inhibits the reaction of L to form M. ∙ Q inhibits the reaction of O to form P. ∙ S inhibits the reaction of O to form R. Which reaction would prevail if both Q and S were present in the cell in high concentrations?

C) L → N

Experiment - Based on this information, which of the following is correct?

C) Succinate is the substrate, and fumarate is the product.

Which of the following is (are) true for anabolic pathways?

C) They consume energy to build up polymers from monomers.

Which of the following is an example of cooperativity?

C) a molecule binding at one unit of a tetramer allowing faster binding at each of the other three

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What is substance X?

C) a substrate

Which of the following is most similar in structure to ATP?

C) an RNA nucleotide

Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in

C) breaking the bond between glucose and fructose and forming new bonds from the atoms of water.

Which of the following represents the activation energy required for a noncatalyzed reaction?

C) c

When you have a severe fever, what may be a grave consequence if this is not controlled?

C) change in the folding of enzymes

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

C) competitive inhibition

Figure 8.1 - Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher?

C) curve 3

What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?

C) energy coupling

SQ - Most cells cannot harness heat to perform work because

C) temperature is usually uniform throughout a cell.

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

C) the activation energy barrier for this reaction cannot be surmounted.

SQ - Some bacteria are metabolically active in hot springs because

C) their enzymes have high optimal temperatures.

An important group of peripheral membrane proteins are enzymes, such as the phospholipases that attack the head groups of phospholipids leading to the degradation of damaged membranes. What properties must these enzymes exhibit?

C) water solubility

The mathematical expression for the change in free energy of a system is △G =△H-T△S. Which of the following is (are) correct?

C) △G is the change in free energy.

Figure 8.3 - Which of the following is the most correct interpretation of the figure?

D) ATP is a molecule that acts as an intermediary to store energy for cellular work.

How can one increase the rate of a chemical reaction?

D) Add a catalyst.

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?

D) As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.

Which of the following statements is representative of the second law of thermodynamics?

D) Cells require a constant input of energy to maintain their high level of organization.

Which of the following is true of enzymes?

D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

Which of the following statements is a logical consequence of the second law of thermodynamics?

D) Every chemical reaction must increase the total entropy of the universe.

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?

D) It can be added to other molecules in order to activate them.

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

D) It is lost to the environment.

Which of the following is true of metabolism in its entirety?

D) Metabolism is a property of organismal life

Which best describes the reaction?

D) The amount of free energy released as a result of the catalyzed reaction is indicated by "d."

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?

D) The binding of the substrate changes the shape of the enzyme's active site.

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?

D) a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive

Which of the following is an example of potential rather than kinetic energy?

D) a food molecule made up of energy-rich macromolecules

Some enzymatic regulation is allosteric. In such cases, which of the following would usually be found?

D) an enzyme with more than one subunit

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)

D) cofactor necessary for enzyme activity.

Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

D) curve 4

Figure 8.2 - Which of the following represents the △G of the reaction?

D) d

Figure 8.2 - Which of the following would be the same in an enzyme-catalyzed or noncatalyzed reaction?

D) d

Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products?

D) d

Whenever energy is transformed, there is always an increase in the

D) entropy of the universe.

Which curve was most likely generated from an enzyme that requires a cofactor?

E) It is not possible to determine whether an enzyme requires a cofactor from these data.

SQ - If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur?

E) Nothing; the reaction would stay at equilibrium.

When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation?

E) Reactant and product concentrations are not the same

What must be the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in DNA and RNA?

E) There is no difference.

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

E) catabolism

In coupled reactions, in which direction would the endergonic reaction be driven relative to the clockwise direction of the ATP reaction above and shown in the figure?

E) it would be shown in a clockwise direction at the top of the figure

What is the change in free energy of a system at chemical equilibrium?

E) no net change

Assume that the reaction has a △G of -5.6 kcal/mol. Which of the following would be true?

The reaction would result in an increase in entropy (S) and a decrease in the total energy content (H) of the system.