Ch. 8 Dynamic Study module

What is important about enzymes?

-acts as a catalyst -lowers the activation energy barrier -enzyme cannot change the delta G for a reaction -Heat can speed a reaction, but can be inappropriate by denaturing enzymes and kills cells

Why are inhibitors may be reversible or irreversible?

-if the inhibitor attatches to the enzyme by covalent bonds inhibition is irreversible -Many enzyme inhibitors, however, bind to the enzyme by weak interactions, in which case inhibition is reversible

As ATP begins to build up in a cell, metabolism slows down. How does this happen? ATP binds to the active sites of many of the enzymes involved in metabolism, causing them to stop functioning. ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function. Excess ATP causes many of the enzymes involved in metabolism to denature. ATP acts as an activator, increasing the rate of its production.

ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function

Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible? ADP and ATP are stored in large amounts in a cell. ATP can be regenerated by the addition of a phosphate group to ADP. ADP is generated by the addition of a phosphate group to ATP. None of the listed responses is correct. The hydrolysis of ATP is an irreversible reaction.

ATP can be regenerated by the addition of a phosphate group to ADP

How is ATP connected to its inhibitor?

Allosteric inhibitor (not an activator)

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. Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules. The flow of energy between catabolic and anabolic pathways is reversible. 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. The enzyme functions best at both low and high temperatures. High temperature provides the optimal environment in which this enzyme functions. Temperature has no effect on enzyme function.

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? Both are nonprotein enzyme helpers; but most coenzymes are metal ions, and most cofactors are organic molecules. Cofactors that are metal ions activate enzymes, but coenzymes deactivate them. 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 cofactors and coenzymes act as allosteric inhibitors to various enzymes.

Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor

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. 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 activation energy 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 .

Which of the following statements about enzymes is true? Enzymes increase the rate of a reaction by raising the activation energy for reactions. All of the listed responses are correct. 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 more heat that is added to a reaction, the faster the enzymes will function.

Enzymes speed up the rate of the reaction without changing the delta G 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? Chemical reactions in cells are always at equilibrium. Anabolic reactions drive catabolic reactions. Exergonic reactions drive endergonic reactions. Endergonic and exergonic reactions occur independently of each other. Endergonic reactions drive exergonic reactions.

Exergonic reactions drive endergonic reactions

Feedback inhibition is...

Feedback inhibition is a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway. Feedback inhibition thereby prevents the cell from making more product than is necessary and this wasting chemical resources

Which of the following reactions would be endergonic? HCl → H+ + Cl ATP → ADP + Pi Glucose + fructose → sucrose C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

Glucose + fructose → sucrose

Which of the following statements is correct regarding kinetic and potential 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. Chemical energy is a type of kinetic energy, and thermal energy is a type of potential energy. Potential energy cannot be converted to kinetic energy. 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 statements about the active site of an enzyme is correct? Coenzymes are rarely found in the active site of an enzyme. The structure of the active site is not affected by changes in temperature. The active site has a fixed structure (shape). 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.

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Which of the following statements is correct regarding ATP? The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups. The energy in an ATP molecule is released from the adenine group. ATP cannot transfer energy to other molecules. The energy in an ATP molecule is released from the ribose group. 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

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? Neutral pH provides the optimal environment in which this enzyme functions. Low pH causes the enzyme to denature, and neutral pH causes the enzyme to function normally. pH has no effect on enzyme function. The enzyme functions best at both low and neutral pH. The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.

The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional

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 cooperativity competitive inhibition feedback inhibition noncompetitive inhibition

allosteric regulation -Allosteric regulation is the term used to describe any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site. It may result in either inhibition or stimulation of an enzyme's activity.

Coenzymes and cofactors...

are both nonprotein helpers for catalytic activity. organic cofactors are coenzymes. most vitamins act as coenzymes

How does ATP drive mechanical work inside a cell? By providing free energy to facilitate the formation of polymers from monomers By phosphorylating a transport protein By removing free energy from a chemical reaction By binding to motor proteins By removing a phosphate from a transport protein

by binding to motor proteins. -ATP hydrolysis leads to changes in a protein's shape and often its ability to bind to another molecule

How does ATP drive transport work inside a cell? By phosphorylating a transport protein By removing free energy from a chemical reaction By binding to motor proteins By removing a phosphate from a transport protein By providing free energy to facilitate the formation of polymers from monomers

by phosphorylating a transport protein -ATP powers transport and mechanical work -ATP hydrolysis leads to changes in a protein's shape and often its ability to bind to another molecule

Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors? Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site. Inhibitors always bind irreversibly to an enzyme. Neither type of inhibitor affects enzyme function. Only competitive inhibitors affect enzyme function. Competitive inhibitors do not bind directly to the active site of an enzyme while noncompetitive inhibitors do. I

competitive inhibitors bind to the active site of an while noncompetitive inhibitors bind to an enzyme away from the active site

Which of the following states the relevance of the first law of thermodynamics to biology? Energy can be freely transformed among different forms as long as the total energy is conserved. The total energy taken in by an organism must be greater than the total energy stored or released by the organism. Energy is destroyed as glucose is broken down during cellular respiration. Living organisms must increase the entropy of their surroundings. Photosynthetic organisms produce energy in sugars from sunlight.

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. In this situation, the second law of thermodynamics must not apply. 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. The first law of thermodynamics is being violated.

energy input into the organism must be occurring to drive the decrease in entropy

Which of the following statements about enzymes is true? The more heat that is added to a reaction, the faster the enzymes will function. All of the listed responses are correct. Enzymes increase the rate of a reaction by raising the activation energy for reactions. 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.

enzymes speed up the rate of the reaction without changing the delta G for the reaction

ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________. denaturing feedback inhibition positive feedback competitive inhibition cooperativity

feedback inhibition

Enzyme activity is affected by pH because __________. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier most substrates don't function well at high or low pH 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 changes in pH can cause loss of cofactors from the enzyme

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

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 active site the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier low pH will denature all enzymes changes in pH can cause loss of cofactors from the enzyme 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

Just as each enzyme has an optimal temperature...

it also has a pH at which it is most active. Enzyme activity is affected by pH because high or llow pH may disrupt hydrogen bolding or ionic interactions that change the shape of the active site.

What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components? Positive Neutral Negative Zero

positive

An exergonic (spontaneous) reaction is a chemical reaction that __________. occurs only when an enzyme or other catalyst is present releases energy when proceeding in the forward direction cannot occur outside of a living cell leads to a decrease in the entropy of the universe is common in anabolic pathways

releases energy when proceeding in the forward direction

In general, the hydrolysis of ATP drives cellular work by __________. releasing heat changing to ADP and phosphate lowering the free energy of the reaction acting as a catalyst releasing free energy that can be coupled to other reactions

releasing free energy that can be coupled to other reactions

Which of these statements about enzyme inhibitors is true? The action of inhibitors may be reversible or irreversible. A noncompetitive inhibitor does not change the shape of the active site. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback. A competitive inhibitor binds to the enzyme at a place that is separate from the active site. Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory

the action of inhibitors may be reversible or irreversible

Which of the following is changed by the presence of an enzyme in a reaction? The G value for the reactants The G value for the products The sign of ΔG The magnitude of ΔG The activation energy

the activation energy (enzymes lower it)

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? All of the listed responses are correct 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. None of the listed responses is correct.

the aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water

How is energy attained by ATP?

the bonds between the 3 phosphate groups of ATP can be broken down by hydrolysis. The reaction is exergonic and releases -7.3 kcal of energy per mole of ATP hydrolyzed

Which of the following statements is correct regarding ATP? The energy in an ATP molecule is released from the ribose group. The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups. ATP cannot transfer energy to other molecules. ATP molecules do not release free energy when hydrolyzed. 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

What best characterizes the role of ATP in cellular metabolism? The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate. It is catabolized to carbon dioxide and water. The ΔG associated with its hydrolysis is positive. The charge on the phosphate group of ATP tends to make the molecule very water-soluble. 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