What is the change in free energy of a system at chemical equilibrium?
no net change
Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell.
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?
the ability of an enzyme to form a template for holding and joining molecules
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
activation energy
The mathematical expression for the change in free energy of a system is G =H-T S. Which of the following is (are) correct?
G is the change in free energy.
For living organisms, which of the following is an important consequence of the first law of thermodynamics?
The organism ultimately must obtain all of the necessary energy for life from its environment.
Which of the following is true of metabolism in its entirety?
Metabolism is a property of organismal life
Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction.
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?
The binding of the first two molecules must cause a 3-dimensional change that opens another active site on the enzyme.
Which of the following statements is representative of the second law of thermodynamics?
Cells require a constant input of energy to maintain their high level of organization.
Which of the following statements is (are) true about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme.
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?
water solubility
When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?
It can be added to other molecules in order to activate them.
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)
cofactor necessary for enzyme activity.
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
Which of the following is most similar in structure to ATP?
an RNA nucleotide
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following bests describes the reaction?
negative G, spontaneous
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following represents the G of the reaction?
d
Which of the following statements is a logical consequence of the second law of thermodynamics?
Every chemical reaction must increase the total entropy of the universe.
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?
Reactant and product concentrations are not the same
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?
-20 kcal/mol
According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?
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?
a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive
How can one increase the rate of a chemical reaction?
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?
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 is considered an open system?
an organism
The organization of organisms has become increasingly complex with time. This statement
is consistent with the second law of thermodynamics.
Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in
breaking the bond between glucose and fructose and forming new bonds from the atoms of water.
Which of the following statements is true concerning catabolic pathways?
They are usually coupled with anabolic pathways to which they supply energy in the form of ATP.
A chemical reaction that has a positive G is correctly described as
endergonic
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
Refer to Figure 8.1 to answer the following questions.
Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?
curve 4
Which of the following is (are) true for anabolic pathways?
Which of the following is (are) true for anabolic pathways?
Which of the following is an example of potential rather than kinetic energy?
a food molecule made up of energy-rich macromolecules
Whenever energy is transformed, there is always an increase in the
entropy of the universe
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?
There is no difference
Refer to Figure 8.1 to answer the following questions.
Which curve was most likely generated from an enzyme that requires a cofactor?
It is not possible to determine whether an enzyme requires a cofactor from these data.
A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because
the activation energy barrier for this reaction cannot be surmounted.
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
by changing the shape of a reactant
The next questions are based on the following information.
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?
a substrate