Chapter 8
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? -40 kcal/mol -20 kcal/mol -10 kcal/mol +20 kcal/mol
-20 kcal/mol
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____. a catabolic pathway a pathway that occurs in animal cells but not plant cells an endergonic pathway a pathway that converts organic matter into energy a pathway in which the entropy of the system decreases
A catabolic pathway
Chemical equilibrium is relatively rare in living cells because metabolic pathways are interconnected. Which of the following statements describes an example of a reaction that may be at chemical equilibrium in a cell? an exergonic reaction in which the free energy at equilibrium is higher than the energy content of the reaction at any point away from equilibrium an exergonic reaction in which the entropy change in the cell is precisely balanced by an opposite entropy change in the cell's surroundings an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment a chemical reaction in which neither the reactants nor the products are being produced or consumed in any metabolic pathway at that time in the cell
A chemical reaction in which neither the reactants nor the products are being produced or consumed in any metabolic pathway at that time in the cell
Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as _____. an allosteric activator of the enzyme a coenzyme derived from a vitamin a noncompetitive inhibitor of the enzyme a cofactor necessary for enzyme activity
A cofactor necessary for enzyme activity
Which of the following statements is consistent with the second law of thermodynamics? A gain of free energy in a system is always associated with conversion of energy from one form to another. Without an input of energy, the entropy of an organism would tend to decrease over time. A constant input of energy is required to maintain the high level of cellular organization. Every energy transformation performed by an organism decreases the entropy of the universe.
A constant input of energy is required to maintain the high level of cellular organization
Which of the following statements about equilibrium of chemical reactions is correct? A reaction that is at equilibrium is not capable of doing any work. Reactions can only go in the direction toward equilibrium. The equilibrium point of a reaction represents the least stable configuration for that reaction. Most reactions in a living cell are close to equilibrium. The equilibrium point is where the system has the highest free energy
A reaction that is at equilibrium is not capable of doing any work
Which of the following is the most correct interpretation of the figure? ATP is a molecule that acts as an intermediary to store energy for cellular work. ADP + Pi are a set of molecules that store energy for catabolism. Pi acts as a shuttle molecule to move energy from ATP to ADP. Energy from catabolism can be used directly for performing cellular work.
ATP is a molecule that acts as an intermediary to store energy for cellular work
Which of the following statements describes a central role that ATP plays in cellular metabolism? ATP provides energy coupling between exergonic and endergonic reactions. Hydrolysis of ATP provides an input of free energy for exergonic reactions. Its terminal phosphate bond is stronger than most covalent bonds in other biological macromolecules. Hydrolysis of the terminal phosphate group stores free energy that is used for cellular work.
ATP provides energy coupling between exergonic and endergonic reactions
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting? ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient. ATPase activity must be transferring Pi to the SR to enable this to occur. ATPase activity must be powering an inflow of calcium from the outside of the cell into the SR. ATPase activity must be opening a channel for the calcium ions to diffuse back into the SR along the concentration gradient.
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient
Which of the following molecules is most similar in structure to ATP? a pentose sugar a DNA nucleotide an RNA nucleotide an amino acid with three phosphate groups attached
An RNA nucleotide
How does an enzyme increase the rate of the chemical reaction it catalyzes? An enzyme reduces the free-energy change (ΔG) of the reaction it catalyzes. An enzyme's active site binds only the reactants, and not the products of a reaction, pushing the equilibrium for the reaction far to the right. An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.
An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes
Which of the following statements is an important consequence of the first law of thermodynamics for a living organism? Organisms grow by converting energy into organic matter. The energy content of an organism is constant. The entropy of an organism decreases with time as the organism grows in complexity. An organism ultimately must obtain all of the necessary energy for life from its environment.
An organism ultimately must obtain all of the necessary energy for life from its environment
Which of the following metabolic processes can occur without a net influx of energy from some other process? ADP + P i → ATP + H2O 6 CO2 + 6 H2O → C6H12O6 + 6 O2 amino acids → protein C6H12O6 + 6 O2 → 6 CO2 + 6 H2O glucose + fructose → sucrose
C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O
Which of the following statements is a logical consequence of the second law of thermodynamics? If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe. If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe. Each chemical reaction in an organism must increase the total entropy of the universe. If the entropy of a system decreases, there must be a corresponding decrease in the entropy of the universe.
Each chemical reaction in an organism must increase the total entropy of the universe
Which of the following characteristics is most likely to be associated with an enzyme that catalyzes two different chemical reactions? Either the enzyme has two distinct active sites or the substrates involved in the two reactions have very similar structures. The enzyme is composed of at least two subunits. The enzyme is subject to competitive inhibition and allosteric regulation. The enzyme contains α-helices and β-pleated sheets.
Either the enzyme has two distinct active sites or the substances involved in the two reactions have very similar structures
Which of the following statements about enzyme function is true? Enzyme function is generally increased if the three-dimensional structure or conformation of an enzyme is altered. Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. Enzymes increase the rate of chemical reactions by providing activation energy to the substrate. Enzymes increase the rate of chemical reactions by lowering activation energy barriers.
Enzymes increase the rate of chemical reactions by lowering activation energy barriers
The mathematical expression for the change in free energy of a system is ΔG = ΔH - T ΔS. Which of the following statements is correct? ΔH is the change in entropy, the energy available to do work. ΔG is the change in free energy. ΔS is the change in enthalpy, a measure of randomness. T is the temperature in degrees Celsius.
G is the change in free energy
Enzymes are described as catalysts, which means that they _____. are proteins provide activation energy for the reactions they facilitate increase the rate of a reaction without being consumed by the reaction increase the free energy of the reactants to make the reaction go faster can alter the free energy change (ΔG) for a chemical reaction
Increase the rate of reaction without being consumed by the reaction
Which of the following statements about the evolution of life on Earth, from simple prokaryote-like cells to multicellular eukaryotic organisms, is true? By resulting in such diversity and complexity of life, it is an exception to the second law of thermodynamics. It has occurred in accordance with the laws of thermodynamics and resulted in a substantial increase in the entropy of the planet. It has occurred in accordance with the laws of thermodynamics and resulted in a substantial increase in the total energy in the universe. It has occurred in accordance with the laws of thermodynamics and resulted in a substantial decrease in the entropy of the planet.
It has occurred in accordance with the laws of thermodynamics and resulted in a substantial decrease in the entropy of the planet
Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction. When a glucose molecule is catabolized to CO2 and H2O, chemical energy is lost. Light energy is converted to chemical energy during photosynthesis. A photosynthetic cell within a plant leaf produces chemical energy, stored within glucose molecules.
Light energy is converted to chemical energy during photosynthesis
In a metabolic pathway, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect of malonic acid. What role does malonic acid play with respect to succinate dehydrogenase? Malonic acid is a competitive inhibitor. Malonic acid is an allosteric regulator. Malonic acid blocks the binding of fumarate. Malonic acid is a noncompetitive inhibitor.
Malonic acid is a competitive inhibitor
Which of the following statements is true of metabolism in its entirety in all organisms? Metabolism consists of all the energy transformation reactions in an organism. Metabolism depends on a constant supply of energy from food. Metabolism uses all of an organism's resources. Metabolism manages the increase of entropy in an organism.
Metabolism consists of all the energy transformation reactions in an organism
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes? The active site of the enzyme can provide a microenvironment with a different pH that facilitates the reaction. The binding of two substrates in the active site provides the correct orientation for them to react to form a product. Binding of the substrate to the active site can stretch bonds in the substrate that need to be broken. The active site can provide heat from the environment that raises the energy content of the substrate. The enzyme binds a cofactor that interacts with the substrate to facilitate the reaction
The active site can provide heat from the environment that raises the energy content of the substrate
Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst? The catalyzed reaction will be slower. The catalyzed reaction will have the same Δ_G_. The catalyzed reaction will have higher activation energy. The catalyzed reaction will consume all of the catalyst.
The catalyzed reaction will have the same delta G
The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation? The compound reduces disulfide bonds, causing the enzyme molecules to partially unfold. The compound causes a cofactor to be lost from the enzyme. The compound is a competitive inhibitor. The compound is a negative allosteric regulator. The compound forms a covalent bond with one of the amino acid residues needed for enzyme activity.
The compound is a competitive inhibitor
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy? the energy associated with a gradient of ions across a membrane: kinetic energy the motion of individual molecules: potential energy the covalent bonds of a sugar molecule: potential energy the energy related to the height of a bird above the ground: kinetic energy the heat released from a living organism: potential energy
The covalent bonds of a sugar molecule: potential energy
Which of the following statements about ATP (adenosine triphosphate) is correct? The hydrolysis of ATP is an endergonic process. Almost all of the free energy released on the hydrolysis of ATP is released as heat. The hydrolysis of ATP can supply energy needed for catabolic pathways. The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways. The energy release on hydrolysis of ATP is the result of breaking a bond between the ribose and a phosphate group.
The cycling between ATP and ADP+Pi provides an energy coupling between catabolic and anabolic pathways
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? Living organisms are able to transform chemical energy into entropy. As a consequence of growth, the decrease in entropy of the organism is associated with a corresponding decrease in the entropy of the universe. The decrease in entropy is associated with growth of an organism. As a consequence of growth, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their increased complexity. Living organisms do not obey the second law of thermodynamics, which states that the entropy of an organism increases with each energy transformation.
The decrease in entropy is associated with the growth of an organism. as a consequence of growth, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their increased complexity
Which of the following statements about the role of ATP in cell metabolism is true? The free energy released by ATP hydrolysis has a much more negative ΔG value than the hydrolysis of phosphate groups from other phosphorylated molecules. The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule. The phosphate bonds of ATP are unusually strong bonds.
The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct? The entropy of the universe decreases as the result of this reaction. This is the process of cellular respiration, an anabolic pathway that releases free energy. The entropy of the products is greater than the entropy of the reactants. The free energy lost in this combustion is less than the energy that appears as heat. The reverse reaction, making glucose from water and carbon dioxide, must be an exergonic reaction.
The entropy of the products is greater than the entropy of the reactants
Which of the following would be unlikely to contribute to the substrate specificity of an enzyme? A similar shape exists between a pocket on the surface of the enzyme and a functional group on the substrate. A hydrophobic group on the substrate interacts with several hydrophobic amino acids on the enzyme. The enzyme has an allosteric regulatory site. A positive charge on the substrate is attracted to a negative charge in the active site of the enzyme. The enzyme has the ability to change its configuration in response to the substrate binding.
The enzyme has an allosteric regulatory site
Which of the following statements about feedback regulation of a metabolic pathway is correct? The enzyme that is regulated by feedback inhibition is usually the last enzyme in the metabolic pathway. The products of the pathway become the reactants for a different reaction, and thus products are unable to accumulate. The compound that regulates the pathway acts as a competitive inhibitor or a positive allosteric regulator. The final product of a metabolic pathway is usually the compound that regulates the pathway. Accumulation of the product of the pathway increases further formation of that product.
The final product of a metabolic pathway is usually the compound that regulates the pathway
Which of the following is a chemical reaction? The formation of a covalent bond between two amino acids. The melting of ice. Changing a carbon atom to a nitrogen atom by radioactive decay. Making a hydrogen bond between a water molecule and a sugar molecule.
The formation of a covalent bond between two amino acids
Chemical equilibrium is reached when concentrations of products are higher than the concentrations of reactants. the forward and reverse reactions occur at the same rate. there are equal concentrations of reactants and products. concentrations of reactants and products remain the same.
The forward and reverse reactions occur at the same rate
Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law? The organism must ultimately obtain all the necessary energy for life from its environment. Organisms are unable to transform energy from the different states in which it can exist. The energy content of an organism is constant except for when its cells are dividing. The entropy of an organism decreases with time as the organism grows in complexity.
The organism must ultimately obtain all the necessary energy for life from its environment
Which of the following statements is true for all exergonic reactions? The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. The reaction proceeds with a net release of free energy. The products have more total energy than the reactants. A net input of energy from the surroundings is required for the reactions to proceed.
The reaction proceeds with a net release of free energy
Which of the following aspects of enzyme structure is best described by a clasping handshake analogy? the specific manner in which an enzyme folds to form secondary and tertiary structures the specific manner in which an enzyme is denatured by low pH the specific manner in which an enzyme binds substrate the specific manner in which an enzyme interacts with water
The specific manner in which an enzyme binds substrate
Which of the following statements is true for a system at chemical equilibrium? The system releases energy at a steady rate. The system can do no work. The system consumes energy at a steady rate. The kinetic energy of the system is zero.
The system can do no work
Some bacteria are metabolically active in hot springs because their enzymes have high optimal temperatures. high temperatures make catalysis unnecessary. they are able to maintain a lower internal temperature. their enzymes are completely insensitive to temperature. they use molecules other than proteins or RNAs as their main catalysts.
Their enzymes have high optimal temperatures
Which of the following statements describes a common characteristic of catabolic pathways? They require energy from ATP hydrolysis to break down polymers into monomers. They are exergonic and provide energy that can be used to produce ATP from ADP and Pi. They combine small molecules into larger, more energy-rich molecules. They are endergonic and release energy that can be used for cellular work.
They are exergonic and provide energy that can be used to produce ATP from ADP and Pi
Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization? They can more readily encounter and phosphorylate other membrane proteins. ATP is more abundant near the plasma membrane. Membrane localization lowers the activation energy of the phosphorylation reaction. They flip back and forth across the membrane to access target proteins on either side.
They can more readily encounter and phosphorylate other membrane proteins
Which of the following statements about anabolic pathways is true? They consume energy to build up polymers from monomers. They release energy by degrading polymers to monomers. They decrease the entropy of the organism and its environment. They are usually spontaneous chemical reactions.
They consume energy to build up polymers from monomers
Which of the following statements is true regarding potential energy and kinetic energy? Water at the top of a dam has kinetic energy; water falling through a dam has potential energy. The moving water performs work by moving the blades of turbines in the dam to generate electricity. Water gains kinetic energy as it falls through a dam; water uses potential energy as it moves the blades of turbines in the dam to generate electricity. Water at the top of a dam has potential energy; water falling through a dam has kinetic energy. The moving water performs work by moving the blades of turbines in the dam to generate electricity. Water gains potential energy as it falls through a dam; water uses kinetic energy as it moves the blades of turbines in the dam to generate electricity.
Water at the top of a dam has potential energy; water falling through a dam has kinetic energy. The moving water preforms work by moving the blades of turbines in the dam to generate electricity
Which statement about the binding of enzymes and substrates is correct? Substrate molecules fit into the active site of an enzyme like a key fits into a lock. When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape. Substrate molecules bind to the active site of the enzyme only by weak bonds, such as hydrogen bonds or hydrophobic attraction.
When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in change
Which of the following is an example of potential rather than kinetic energy? water rushing over Niagara Falls a molecule of glucose light flashes emitted by a firefly a crawling beetle foraging for food
a molecule of glucose
A series of enzymes catalyze the reactions in the metabolic pathway 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? the product an intermediate an allosteric inhibitor a substrate
a substrate
What is the name of the thermodynamic barrier that must be overcome before products are formed in a spontaneous reaction? activation energy entropy the equilibrium point free energy
activation energy
If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to add more of the enzyme. heat the solution to 90°C. add a noncompetitive inhibitor. add more substrate. add an allosteric inhibitor.
add more of the enzyme
A series of enzymes catalyze the reactions in the metabolic pathway 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. With respect to the enzyme that converts X to Y, substance A functions as ________. an intermediate the substrate a competitive inhibitor an allosteric inhibitor
an allosteric inhibitor
Which of the following types of reactions would decrease the entropy within a cell? catabolic reactions hydrolysis anabolic reactions digestion
anabolic reactions
Which of the following statements describes an example of cooperativity associated with enzyme regulation? one enzyme in a metabolic pathway passing its product to act as a substrate for the next enzyme in the pathway binding of the end product of a metabolic pathway to the first enzyme in the pathway to inhibit the enzyme binding of an ATP molecule along with another substrate molecule in the active site of the enzyme binding a substrate to one subunit of a tetramer stimulates faster binding of substrate to each of the other three subunits
binding of a substrate to each of the other three subunits
Which of the following statements describes a key component of the induced fit hypothesis of enzyme catalysis? Binding of substrate to the active site changes the shape of the active site of an enzyme. Binding of an activator molecule changes the shape of the active site of an enzyme. The conformation of the active site is determined by the tertiary or quaternary structure of the enzyme. Substrate binds to an allosteric site rather than to the active site of an enzyme.
binding of substrate to the active site changes the shape of the active site of an enzyme
How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction? by binding to an allosteric site, thus changing the shape of the active site of the enzyme by binding to the active site of the enzyme, thus preventing binding of the normal substrate by binding to the substrate, thus changing its shape so that it no longer binds to the active site of the enzyme by decreasing the free-energy change of the reaction catalyzed by the enzyme
by binding to an allosteric site, thus changing the shape of the active site of the enzyme
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter the substrate specificity of an enzyme? by changing the three-dimensional conformation of the enzyme by changing the stability of the enzyme by changing the binding site for a noncompetitive inhibitor by changing the optimum pH for the enzyme
by changing the three-dimensional conformation of the enzyme
Which of the following terms most precisely describes the cellular process of breaking down large molecules into smaller ones? catabolism (catabolic pathways) anabolism (anabolic pathways) metabolism dehydration
catabolism (catabolic pathways)
How do cells use the ATP cycle illustrated in the figure? Cells use the cycle to recycle ADP and phosphate. Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis. Cells use the cycle primarily to generate heat. Cells use the cycle to recycle energy released by ATP hydrolysis.
cells use the cycle to recycle ADP and phosphate
Which of the following conditions may be overcome by increasing the substrate concentration in an enzymatic reaction with a fixed amount of enzyme? allosteric inhibition competitive inhibition noncompetitive inhibition the need for a coenzyme
competitive inhibition
HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon? competitive inhibition allosteric regulation noncompetitive inhibition denaturation
competitive inhibitor
A decrease in entropy is associated with which type of reaction? catabolic hydrolysis depolymerization dehydration
dehydration
Which of the following is the strongest evidence that protein structure and function are correlated? Enzymes tend to be globular in shape. Denatured (unfolded) proteins do not function normally. Proteins can readily form hydrogen bonds with water. Proteins have four distinct levels of structure and many functions.
denatured (unfolded) proteins do not function normally
For the enzyme-catalyzed reaction shown in the figure, if the initial reactant concentration is 1.0 micromolar, which of these treatments will cause the greatest increase in the rate of the reaction? doubling the activation energy needed increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2 cooling the reaction by 10°C doubling the enzyme concentration
doubling the enzyme concentration
A chemical reaction that has a positive ΔG is best described as _____. spontaneous exergonic endergonic enthalpic
endergonic
Which of the following statements describes the first law of thermodynamics? The entropy of the universe is decreasing. Energy cannot be transferred or transformed. The entropy of the universe is constant. Energy cannot be created or destroyed.
energy cannot be created or destroyed
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _______ is to _______. exergonic; spontaneous entropy; enthalpy exergonic; endergonic free energy; entropy work; energy
exergonic; endergonic
The relationship between catabolism and anabolism is most similar to the relationship between which of the following pairs of terms? exergonic; endergonic free energy; entropy exergonic; spontaneous work; free energy
exergonic; endergonic
________ is a regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme that catalyzes an early step in the pathway. Allosteric inhibition Feedback inhibition Metabolic inhibition Cooperative inhibition
feedback inhibition
Why do hydrolysis reactions occur more readily in solution than dehydration reactions? Hydrolysis reactions are exergonic and decrease entropy of the system. Hydrolysis reactions are endergonic and increase entropy of the system. Hydrolysis reactions are exergonic and increase entropy of the system. Hydrolysis reactions increase G, or Gibbs free energy of the system.
hydrolysis are exergonic and increase entropy of the system
Which of the following is a primary function of the active site of an enzyme? It is activated by the presence of the end product of the metabolic pathway in which the enzyme is involved. It binds noncompetitive inhibitors of the enzyme. It binds allosteric regulators of the enzyme. It catalyzes the reaction associated with the enzyme.
it catalyzes the reaction associated with the enzyme
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? It is used to power yet more cellular work. It is lost to the environment. It is used to generate ADP from nucleotide precursors. It is captured to store energy as more ATP.
it is lost to the environment
Characterization of the complete three-dimensional structure of a newly purified protein suggests that it catalyzes the breakdown of a large substrate. The protein consists of a single polypeptide chain. It has a large pocket that appears to be the binding site for the substrate and a smaller indentation that appears to be the binding site for a regulatory molecule. What do these structural observations suggest about the mechanism by which the activity of this protein is likely regulated? It is probably an enzyme that is regulated by competitive inhibition. It is probably an enzyme that is regulated by noncompetitive inhibition. It is probably an enzyme that is regulated by cooperativity. It is probably a multi-subunit enzyme that is regulated by allosteric regulation.
it is probably an enzyme that is regulated by noncompetitive inhibition
When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell? It enters the nucleus to be incorporated in a nucleotide. It may be used to form a phosphorylated intermediate. It is secreted as waste. It is used only to regenerate more ATP.
it may be used to form a phosphorylated intermediate
In addition to activating or inhibiting enzymes through allosteric regulation, what other means does a cell use to control enzymatic activity? altering internal pH assembly of enzymes into large aggregates localization of enzymes into specific organelles or membranes secretion of enzymes out of the cell
localization of enzymes into specific organelles or membranes
Why is the ΔG of ATP hydrolysis in the cell about twice as great as the ΔG of ATP hydrolysis in a test tube under standard conditions? ATP hydrolysis in cells is catalyzed by enzymes, whereas the reaction in a test tube occurs spontaneously. A cell is an open system, whereas a test tube is a closed system. ATP hydrolysis in a test tube releases more heat than ATP hydrolysis associated with cellular metabolism. Reactant and product concentrations in the test tube are different from those in the cell.
reactant and product concentrations in the test tube are different from those in the cell
In a metabolic pathway, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect of malonic acid. Which of the following statements correctly describes the role played by molecules described in the reaction? Succinate dehydrogenase is the enzyme, and malonic acid is the substrate in the reaction. Succinate dehydrogenase is the enzyme, and fumarate is the substrate in the reaction. Fumarate is the product, and malonic acid is a noncompetitive inhibitor in the reaction. Succinate is the substrate, and fumarate is the product in the reaction.
succinate is the substrate, and fumarate is the product in the reaction
Most cells cannot harness heat to perform work because heat must remain constant during work. heat can never be used to do work. heat is not a form of energy. temperature is usually uniform throughout a cell. cells do not have much heat; they are relatively cool.
temperature is usually uniform throughout a cell
Most cells cannot harness heat to perform work because _____. temperature is usually uniform throughout a cell heat must remain constant during work heat can never be used to do work heat is not a form of energy
temperature is usually uniform throughout a cell
