Ch. 6: Into to Metabolism Flashcards
Which of the following is an endergonic reaction?
Glucose + fructose → sucrose
Which of these statements about enzyme inhibitors is true?
The action of competitive inhibitors may be reversible or irreversible.
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
Which of the following is changed in a reaction by the action of an enzyme?
The activation energy
Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?
The continuous removal of the products of a pathway to be used in other reactions and the input of free energy from outside the pathway
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.
Which of the following metabolic processes can occur without a net influx of energy from some other process?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O [CHO + 6O > 6 CO 6 H2O]
Which of the following environments or actions would not affect the rate of an enzyme reaction?
None of the listed responses is 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
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
Most cells cannot harness heat to perform work because __________.
temperature is usually uniform throughout a cell
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 has anything to do with the speed of a reaction. (speed determined by Activation Energy)
In general, the hydrolysis of ATP drives cellular work by __________.
releasing free energy that can be coupled to other reactions
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.
What is meant by the “induced fit” of an enzyme?
The enzyme changes its shape slightly as it binds the substrate.
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________.
exergonic; endergonic
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 enzyme’s active site
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 best characterizes the functional role of ATP in cellular metabolism?
The free energy released by ATP hydrolysis is coupled to endergonic processes via the formation of a phosphorylated intermediate.
The formation of glucose-6-phosphate from glucose is an endergonic reaction and would, therefore, be coupled to which of the following reactions or pathways?
The hydrolysis of ATP
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.
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.
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.
If the entropy of a living organism is decreasing, which of the following is also occurring?
Energy is being supplied to the organism.
Some bacteria are metabolically active in hot springs because __________.
their enzymes have high optimal temperatures
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
In general, the hydrolysis of ATP drives cellular work by __________.
releasing free energy that can be coupled to other reactions
If the entropy of a living organism is decreasing, which of the following is also occurring?
Energy is being supplied to the organism.
What is meant by the “induced fit” of an enzyme?
The enzyme changes its shape slightly as it binds the substrate.
