Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following would be the same in an enzyme-catalyzed or noncatalyzed reaction?
d
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following represents the activation energy required for a noncatalyzed reaction?
c
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following represents the activation energy required for the enzyme-catalyzed reaction?
b
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 ΔG, spontaneous
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?
+ΔH, -ΔS, +ΔG
Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following represents the ΔG of the reaction?
d
Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
compartmentalization of enzymes into defined organelles
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is lost to the environment
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
Some enzymatic regulation is allosteric. In such cases, which of the following would usually be found?
an enzyme with more than one subunit
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as
feedback inhibition
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.
Assume that the reaction has a ΔG 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
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
Which of the following metabolic processes can occur without a net influx of energy from some other process?
C6H12O6 + 6 O2 6 CO2 + 6H2O
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
activation energy
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
If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur?
Nothing; the reaction would stay at equilibrium
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
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?
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________.
exergonic; endergonic
When you have a severe fever, what may be a grave consequence if this is not controlled?
change in the folding of enzymes
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following terms best describes the reaction?
exergonic
Refer to Figure 8.1 to answer the following questions.
Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher?
curve 3
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
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
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
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
Use Figure 8.3 to answer the following questions.
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?
it would be shown in a clockwise direction at the top of the figure
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:
+ΔG, +ΔH, -ΔS
The following questions are based on the reaction A + B C + D shown in Figure 8.2.
Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products?
d
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 considered an open system?
an organism
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
by changing the shape of a reactant
Which of the following is an example of potential rather than kinetic energy?
a food molecule made up of energy-rich macromolecules
How can one increase the rate of a chemical reaction?
Add a catalyst
Which of the following types of reactions would decrease the entropy within a cell?
dehydration reactions
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