Bio CH 8
Which of the following states the relevance of the first law of thermodynamics to biology? Because living things consume energy, the total energy of the universe is constantly decreasing. Photosynthetic organisms produce energy in sugars from sunlight. Energy can be freely transformed among different forms as long as the total energy is conserved.
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? The entropy of the organism's environment must also be decreasing. Heat is being used by the organism as a source of energy. Energy input into the organism must be occurring to drive the decrease in entropy.
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 change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the net energy output. Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the activation energy. Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.
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 reactions would be endergonic? ATP → ADP + Pi Glucose + fructose → sucrose HCl → H+ + Cl
Glucose + fructose → sucrose
Which of the following statements is correct regarding kinetic and potential energy? Potential energy cannot be converted to kinetic energy. Potential energy is related to the relative motion of objects, and kinetic energy is the energy that matter possesses because of its location or structure. Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.
Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.
Which of the following is true regarding metabolic pathways? Metabolic pathways consist of a single chemical reaction. Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme. Metabolic pathways are not important to a cell's ability to function.
Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.
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. All types of cellular respiration produce ATP. Cellular respiration releases some energy as heat.
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
Describe the forms of energy found in an apple as it grows on a tree, then falls, then is digested by someone who eats it.
The apple has potential energy in its position hanging on the tree, and the sugars and other nutrients it contains have chemical energy. The apple has kinetic energy as it falls from the tree to the ground. Finally, when the apple is digested and its molecules broken down, some of the chemical energy is used to do work, and the rest is lost as thermal energy.
Which of the following statements is correct regarding ATP? ATP molecules do not release free energy when hydrolyzed. The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups. ATP cannot transfer energy to other molecules.
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
Which of the following statements is correct regarding ATP? The energy in an ATP molecule is released from the adenine group. The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups. ATP cannot transfer energy to other molecules.
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme? Low pH causes the enzyme to denature, and neutral pH causes the enzyme to function normally. The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional. pH has no effect on enzyme function.
The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.
Kinetic energy due to the random motion of atoms and molecules; energy in its most random form. See also heat.
Thermal Energy
The reactant on which an enzyme works.
substrate
Which of the following has more free energy: glutamic acid+ammonia+ATP or glutamine+ADP+Ⓟi ? Explain your answer.
A set of coupled reactions can transform the first combination into the second. Since this is an exergonic process overall, ΔG is negative and the first combination must have more free energy
Many spontaneous reactions occur very slowly. Why don't all spontaneous reactions occur instantly?
A spontaneous reaction is a reaction that is exergonic. However, if it has a high activation energy that is rarely attained, the rate of the reaction may be low.
Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible? ATP can be regenerated by the addition of a phosphate group to ADP ADP and ATP are stored in large amounts in a cell. ADP is generated by the addition of a phosphate group to ATP.
ATP can be regenerated by the addition of a phosphate group to ADP.
How does ATP typically transfer energy from an exergonic to an endergonic reaction in the cell?
ATP usually transfers energy to an endergonic process by phosphorylating (adding a phosphate group to) another molecule. (Exergonic processes, in turn, phosphorylate ADP to regenerate ATP.)
Which of the following correctly states the relationship between anabolic and catabolic pathways? Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways. Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme? At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional. Low temperatures cause the enzyme to denature, and high temperatures cause the enzyme to move too fast to bind to its substrate. High temperature provides the optimal environment in which this enzyme functions.
At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.
Which of the following statements correctly describes cofactors and coenzymes? Neither cofactors nor coenzymes assist enzyme function. Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor. Both are nonprotein enzyme helpers; but most coenzymes are metal ions, and most cofactors are organic molecules.
Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.
How would the processes of catabolism and anabolism relate?
Catabolism breaks down organic molecules, releasing their chemical energy and resulting in smaller products with more entropy, as when moving from the top to the bottom of Figure 8.5c. Anabolism consumes energy to synthesize larger molecules from simpler ones, as when moving from the bottom to the top of part (c).
Cellular respiration uses glucose and oxygen, which have levels of free energy, and releases CO2, and water, which have low levels of free energy. Is. cellular respiration spontaneous or not? Is it exergonic or endergonic? What happens to the energy released from glucose?
Cellular respiration is a spontaneous and exergonic process. The energy released from glucose is used to do work in the cell or is lost as heat.
Which of the following statements about enzymes is true? Enzymes increase the rate of a reaction by raising the activation energy for reactions. Enzymes speed up the rate of the reaction without changing the ΔG for the reaction. Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme.
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.
The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling? Endergonic reactions drive exergonic reactions. Exergonic reactions drive endergonic reactions. Chemical reactions in cells are always at equilibrium.
Exergonic reactions drive endergonic reactions.
Why do enzymes act only on very specific substrates?
Only the specific substrate(s) will fit properly into the active site of an enzyme, the part of the enzyme that carries out catalysis.
What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components? Zero Positive Negative
Positive
Which of the following is changed by the presence of an enzyme in a reaction? The sign of ΔG The activation energy The magnitude of ΔG
The activation energy
Which of the following statements about the active site of an enzyme is correct? The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits. Coenzymes are rarely found in the active site of an enzyme
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
What best characterizes the role of ATP in cellular metabolism? The release of free energy during the hydrolysis of ATP heats the surrounding environment. The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate The charge on the phosphate group of ATP tends to make the molecule very water-soluble.
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
What best characterizes the role of ATP in cellular metabolism? The charge on the phosphate group of ATP tends to make the molecule very water-soluble. It is catabolized to carbon dioxide and water. The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
Some nighttime partygoers wear glow in the dark necklaces. The necklaces. The necklaces in a way that allows two chemicals to react and emit light in the form of chemiluminescence. Is this chemical reaction exergonic or endergonic?
The reaction is exergonic because it releases energy—in this case, in the form of light
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. The process of photosynthesis produces energy that the plant uses to grow. Growth of the crops must occur spontaneously. The entropy of the universe must decrease to account for the increased entropy associated with plant growth.
To obey the first law, the crops must represent an open system.
Enzyme activity is affected by pH because __________. low pH will denature all enzymes high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site most substrates don't function well at high or low pH
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site
An exergonic (spontaneous) reaction is a chemical reaction that __________. is common in anabolic pathways cannot occur outside of a living cell releases energy when proceeding in the forward direction
releases energy when proceeding in the forward direction
An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy. releases; absorbs releases; releases absorbs; releases
releases; absorbs
In general, the hydrolysis of ATP drives cellular work by __________. releasing free energy that can be coupled to other reactions changing to ADP and phosphate releasing heat
releasing free energy that can be coupled to other reactions
